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Old 08-09-2020, 05:04 PM   #1
Rusty_ratchet
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Default Failed Smog

1985 Volvo 240

I took my car in for emissions testing and failed.
The results of the test are below:



I tested the O2 sensor using a labscope. The voltage was alternating between approx 0V and 1V. I also believe it is fast enough.

I checked for vacuum leaks using a smoker. I found a small leak at one of the air intake hose nipples. It was pretty small, but a leak never the less. It is an aftermarket hose and the nipple was deformed into a sort of "D" shape. I still have the original and put it back on. No leaks now, and I'm skeptical that the previous hose had enough of a leak to be a problem.

I measured the temp of the pipe just before and after the catalytic converter. It is 490 F at the front and 550 F at the back. Should the temp be lower at the front?

I pulled the spark plugs and some photos are shown below (1 on the far left, 4 on the far right):





The plugs have 22k miles on them. They were gapped to 0.028" when I installed them and are now 0.032" except for the cylinder 4 plug that is 0.033". This is more wear than I would have expected. I would have thought that it would be closer to 30k miles before they reached their limit. I am using Volvo plugs.

All the plugs look dry, except for the cylinder 4 plug:


There is an exhaust leak at the header pipe. This is after the O2 sensor. Does it make a difference in smog since it is after the O2 sensor?


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Old 08-10-2020, 12:09 AM   #2
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€5 a new cat will pass you.
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Old 08-10-2020, 03:18 AM   #3
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AZ? Cursory visual? Auto-tragic? Drive it on the rollers, yeah?

Don't crack the manifold/get too crazy spraying stuff on it hot hot?

If anything the exhaust leak in that spot is probably helpful/free air injection for the cat for the tailpipe test.

Those late model 85+ DPs kinda suck. Surfacing that flange flat can be a challenger and the late 82-84 style are much better made. Don't forget the bellhousing bracket to go with the early DP.
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Old 08-10-2020, 11:06 AM   #4
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Originally Posted by ZVOLV View Post
€5 a new cat will pass you.
Is that because of the temps at the front and back of the pipe?

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Originally Posted by Kjets On a Plane View Post
AZ? Cursory visual? Auto-tragic? Drive it on the rollers, yeah?

Don't crack the manifold/get too crazy spraying stuff on it hot hot?

If anything the exhaust leak in that spot is probably helpful/free air injection for the cat for the tailpipe test.

Those late model 85+ DPs kinda suck. Surfacing that flange flat can be a challenger and the late 82-84 style are much better made. Don't forget the bellhousing bracket to go with the early DP.
The manifold was not hot. I put a leaf blower at the tailpipe and sprayed soapy water on the joints etc. I also found some leaks at the bend of the header pipe so that that will need to be replaced.

The car is an automatic. What does it mean to drive it on the rollers? My commute was on the freeway until March, and its been driven very little since then. I've probably driven 100 miles in-town since March, and no driving on the freeway.

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Old 08-10-2020, 12:00 PM   #5
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Fix any exhaust leaks before or after (within a 12" or so) the oxygen sensor. Replace your plugs, run some fuel system cleaner through it to help out the injectors, change your oil.... then test.

Temp should be lower at the front of the catalytic converter. The heat gain is from the reaction with the catalyst.
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Old 08-10-2020, 12:45 PM   #6
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Egr car?
Plug the advance and will bring nox down a bit.
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Old 08-10-2020, 01:14 PM   #7
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Originally Posted by culberro View Post
Fix any exhaust leaks before or after (within a 12" or so) the oxygen sensor. Replace your plugs, run some fuel system cleaner through it to help out the injectors, change your oil.... then test.

Temp should be lower at the front of the catalytic converter. The heat gain is from the reaction with the catalyst.
Thank you for the tips. Hopefully the tuneup will help.

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Egr car?
Plug the advance and will bring nox down a bit.
No, the car does not have an EGR.
I can't find a vacuum advance for the distributor. The distributor just has a three-prong electrical plug.
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Old 08-10-2020, 01:32 PM   #8
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Quote:
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Egr car?
Plug the advance and will bring nox down a bit.
Good call. Ive heard of the "put a BB" in there method.


The vac hose goes to the ignition box at the passenger inner fender


Octane increase could bring it down too. Maybe even put a decent amount of E85 in there. Lower combustion temps= lower NOX.

A couple tricks and a retest may do it.

Where is this test? Thats not a CA emissions report.
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Old 08-10-2020, 01:45 PM   #9
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Originally Posted by ZVOLV View Post
Good call. Ive heard of the "put a BB" in there method.


The vac hose goes to the ignition box at the passenger inner fender


Octane increase could bring it down too. Maybe even put a decent amount of E85 in there. Lower combustion temps= lower NOX.

A couple tricks and a retest may do it.

Where is this test? Thats not a CA emissions report.
Thanks, I'll look for it.
I am in Arizona.
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Old 08-10-2020, 02:17 PM   #10
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AZ they let me drive the car on the rollers for the emissions test, was surprised.
Never had a state allow the owner to drive the car/prefer it that way.
Pretty libertarian/awesome place in some ways, not always in others.
Was a joy to skip kalifornia as an Oregonian/MT guy visiting.
Specs are pretty strict/test cars back to 1968, but at least they're not *******s about it like CA.
Tho, I failed once and they took my $12, which I was sore about, but upon re-test was free/passed easily (busted fuel pressure regulator stuck shut).
OR it's free to fail DEQ/fail as many times as you want/don't give them any data/info, but pass is cheap enough.

It was a stick shift car so I kinda wanted to be the one to drive it, it simulated some gentle accelerations/hills/maintain speed/inertia drum dyno.

3rd in the manual car was a little hard to be smooth/maintain speed/not open/shut the throttle as much or rapidly, but 2nd you'd have the thing spun up closer to 3000rpm (25-35mph?) stirring up more crankcase windage, interesting decision tree there.

Didn't want the tech to crunch up what is otherwise the 1 in 100 M47 that doesn't crunch into 1st or anything and is buttery smooth & silent.

Can be a challenge to make them pass a stringent NOX test (don't think Tucson has NOX, but Phx suburbs, yes) on the lean-burn ignition years 83-88 even if the car's tip top tuned up & engine is tight with clean oil/proper valve adjustment etc. Flat-top piston B23 being the most NOX unfriendly, relatively.
M-cam technically passes emissions just a tiny bit cleaner than the T if you live somewhere with really strict emissions dyno tests (SoCal. or Phoenix usually).
I always install the M in the trash if I have a T and I'm doing a T-belt/valve adjustment for power & economy, but it's a consideration, strictly speaking; the factory was thinking emissions with the M and if you get a full live-time 5-gas readout, the M's cleaner on the dyno tests.

No EGR those years. Lowest allowable you can set the timing to is ~10º (well, even with a perfectly tight pre 85 oil wick dist, it'll probably wander + or - 1 degree at idle, even if charging voltage/belts run smooth etc with the mopar ignition.

IDK if they check the timing like CA/are visual Nazis. They just seem to sniff it over/make sure it has a cat/most everything is in place in the engine bay generally (pre-heat hose/whatever) and nothing looks hacked/missing. 10º should be allowable, it's 12º + or - 2 IIRC.
Make sure the early B230 crank pulley hasn't slipped/is accurate before setting timing.

Car may run warm/be prone to overheat in hot weather with the timing set at 9-10, even if the belts don't slip/aren't glazed, alt bushings are good/have a thin helper washer hack/mod & it has a tight tropical can clutch/air guide in place/clean radiator & A/C condenser (if equipped...we got non-A/C DL cars in OR/WA coastal, but I've never seen a non-A/C '85 EFI car in AZ )

Car will pass on ethanol/alcohol easier, might run like crap...with those #s you probably don't need to resort to that or such things.
Make sure the injectors & oil are clean/thing's tuned tip top and maybe retard the timing at idle slightly/to min allowable or BB in the vac line to the mopar box or whatever (car will be a slug/might run a little warm).

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Old 08-10-2020, 02:35 PM   #11
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Originally Posted by Kjets On a Plane View Post
AZ they let me drive the car on the rollers for the emissions test, was surprised.
Never had a state allow the owner to drive the car/prefer it that way.
Pretty libertarian/awesome place in some ways, not always in others.

It was a stick shift car so I kinda wanted to be the one to drive it, it simulated some gentle accelerations/hills/maintain speed/inertia drum dyno.

3rd in the manual car was a little hard to be smooth/maintain speed/not open/shut the throttle as much or rapidly, but 2nd you'd have the thing spun up closer to 3000rpm (25-35mph?) stirring up more crankcase windage, interesting decision tree there.

Didn't want the tech to crunch up what is otherwise the 1 in 100 M47 that doesn't crunch into 1st or anything and is buttery smooth & silent.

Can be a challenge to make them pass a stringent NOX test (don't think Tucson has NOX, but Phx suburbs, yes) on the lean-burn ignition years 83-88 even if the car's tip tip top. No EGR those years. Lowest allowable you can set the timing to is ~10º (well, even with a perfectly tight pre 85 oil wick dist, it'll probably wander + or - 1 degree at idle, even if charging voltage/belts run smooth etc with the mopar ignition), though IDK if they check the timing like CA/are visual Nazis.
Make sure the crank pulley hasn't slipped/is accurate before setting timing.

Car may run warm/be prone to overheat in hot weather with the timing set at 9-10, even if the belts don't slip/aren't glazed, alt bushings are good/have a thin helper washer hack/mod & it has a tight tropical can clutch/air guide in place/clean radiator & A/C condenser (if equipped...we got non-A/C DL cars in OR/WA coastal, but I've never seen a non-A/C '85 EFI car in AZ )
I used to drive the car on rollers for emissions when I was in Tucson, but they haven't let me do that in Phoenix.

The car had pretty good NOx numbers in years past (2.0 to 2.7 over the past 16 years). I haven't seen them check the timing. When I checked the timing, it seemed pretty stable. I should probably check the timing again though, since I did not disconnect the vac advance (I couldn't find it so thought it did not have one).

I replaced the bushings a year or two ago and they are still in pretty good shape. Some of the bushings have a helper washer, and some do not. I'll try to find the ones that don't.

My parents drove a 240 from Seattle to AZ in 1980. It didn't have AC, but they had one put in shortly after moving here :-)
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Old 08-10-2020, 02:47 PM   #12
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Hm, is the thermostat reaching OP temp?
NOX is uneven combustion temp more than anything.
More timing, hot spots, not reaching OP temp, more compression etc make that a challenge if it doesn't have EGR.

Absent EGR they had to really wreck compression ratios/timing advance curves install very warm thermostats & instally dreadful cams in cars in the late 70s to get those engines to pass the NOX standard. Engines got better/newer designs, aluminum heads, better combustion chambers/bore/stroke geometry, coolant flow paths and EGR and more complex controls with better resolution and they didn't have to do such terrible things to the engine bay/band-aid old designs & ruin power & economy.

The lean-burn higher compression mid-80s volvos squeak under when new/when the cat was new, but an EGR LH2.4 car/same engine would limbo under the bar with numbers like 1 or less on that scale, for example.

Could just be a ~200K mile/20+ year old ancient cat is finally letting go even if injectors are clean/cycles on the clean heated 02 sensor fine etc, but I wouldn't throw money at that or ever buy one if I could help it.

That dyno test is often a pretty good truth teller in AZ if anything isn't tip top perfect.
Kinda like smog tests in that way; (nearly) free 5-gas time.
If anything isn't tuned up tip top/engine is burning oil or something's not right for longevity, you'll find out!
Just a cheapskate that refuses to ever buy a cat if it's remotely avoidable, particularly anything aftermarket/cheaply made.

Be glad you don't live in the corrupt new-car-status-symbol-lobby CA police state where they're trying to take your old car away from you/costs a fortune & super inconvenient to pass/get labeled as a gross polluter/presumed guilty of high crimes if you fail.
They've also lowered the NOX standard to lower than when those 83-88 lean-burn cars that already eeked under when the cat was new & rest of the cars were new!
Ex/de-facto entrapment, much?

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Old 08-10-2020, 02:49 PM   #13
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You wanna plug it not disconnect it. It helps bring nox down. Another guy in here says the spring wears out in the advance diaphram device and it over advances the timing. Check your vacuum hoses as well. To the heater controls, evap canister, flame trap etc. Double check the accordion intake tube while your at it.
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Old 08-10-2020, 03:10 PM   #14
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Quote:
Originally Posted by Kjets On a Plane View Post
Hm, is the thermostat reaching OP temp?
NOX is uneven combustion temp more than anything.
More timing, hot spots, not reaching OP temp, more compression etc make that a challenge if it doesn't have EGR.

Absent EGR they had to really wreck compression ratios/timing advance curves install very warm thermostats & instally dreadful cams in cars in the late 70s to get those engines to pass the NOX standard. Engines got better/newer designs, aluminum heads, better combustion chambers/bore/stroke geometry, coolant flow paths and EGR and more complex controls with better resolution and they didn't have to do such terrible things to the engine bay/band-aid old designs & ruin power & economy.

The lean-burn higher compression mid-80s volvos squeak under when new/when the cat was new, but an EGR LH2.4 car/same engine would limbo under the bar with numbers like 1 or less on that scale, for example.

Could just be a ~200K mile/20+ year old ancient cat is finally letting go even if injectors are clean/cycles on the clean heated 02 sensor fine etc, but I wouldn't throw money at that or ever buy one if I could help it.

That dyno test is often a pretty good truth teller in AZ if anything isn't tip top perfect.
Kinda like smog tests in that way; (nearly) free 5-gas time.
If anything isn't tuned up tip top/engine is burning oil or something's not right for longevity, you'll find out!
Just a cheapskate that refuses to ever buy a cat if it's remotely avoidable, particularly anything aftermarket/cheaply made.

Be glad you don't live in the corrupt new-car-status-symbol-lobby CA police state where they're trying to take your old car away from you/costs a fortune & super inconvenient to pass/get labeled as a gross polluter/presumed guilty of high crimes if you fail.

I am using an 87 degree thermostat. The needle on the temp gauge typically sits just below the white dot under normal driving conditions. Typically the highest the needle goes is the white dot.
I try to keep the car in good shape, so am surprised the car didn't pass. Oh well.
I typically change the oil every 2k miles, and use Mobile 1 10w-30. I don't notice the engine burning any oil.

I am going to avoid getting a new cat if possible. If it comes to that then I'll probably get a 50 state compliant cat. I've seen good things about the MagnaFlow cats.

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You wanna plug it not disconnect it. It helps bring nox down. Another guy in here says the spring wears out in the advance diaphram device and it over advances the timing. Check your vacuum hoses as well. To the heater controls, evap canister, flame trap etc. Double check the accordion intake tube while your at it.
That's good to know about the spring wearing out. I'm going to get my timing light and check the vacuum advance hose and timing in a sec.

I checked the vacuum hoses with a smoker. I found a very small leak at one of the intake hose nipples. I fixed the leak, but would be surprised if it was enough to make a difference. The intake hose looks ok.

In regard to the heater controls: I think the hose that goes from the intake to the firewall is used for the heater controls. I disconnected the hose and used a MityVac to draw a vacuum. I let it sit for a while and the vacuum held. That was with the "re-circulation" button depressed. I didn't check it without recirculation. I have noticed that there is a hissing sound when I turn off re-circulation. I assume there is a leak, but only when re-circulation is off.
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Old 08-10-2020, 03:20 PM   #15
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Go with a Walker cat. My magnaflow "failed smog" after only a couple years and the shop BS'd me saying they sent it in for analysis, and it a replacement was declined. I doubt he lifted a finger.


Also, on my 1991 740T, I run almost half a tank of E85 on stock injectors and ECU and it fixes my knock on hard acceleration

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Old 08-10-2020, 03:25 PM   #16
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They sold an updated mopar box & harness for 81-87 cars. Not cheap in the day.
In practice, you can install the '88 mopar box & harness together in 85-87 cars.

Nice upgrade. Timing less wandery, has the sleeves on the pin for the plug installed OE (you're supposed to replace the sleeves if you unplug the box technically/keep the harness & box together per the volvo book).
Map sensor doesn't seem to fail on those.
Though I've had pretty good luck with the mopar box on the cool weather cars, seen more failures on CA cars.

The MAP sensor fails all together electrically and timing is full retarded/car won't pull a hill/overheats or spring can get weak/over-advances timing at cruise, failing NOX, yes.

Plug the vac line, don't disconnect, don't want a vac leak, make sure vac line isn't chafed/doesn't leak with your mity-vac.

If the dist gets oiled at the oil wick and oil is changed often, the dist probably isn't seized in the block in the AZ desert climate probably doesn't have a wobbly shaft. Penitrating oil between the dist/block to get the dist to move to set the timing and gummy gross oil is common in the PNW rainforest...that front corner of the intake side of the block is often filled with all sorts of goo in our climate (moisture trap, has the fan/cold damp air blowing on it here). Probably not even an issue where you are as long as the dist oil wick was oiled to keep the bushing from wearing out in it.

They kinda had it right with the B18/B20; dist out of the damp/in the middle of the nice warm block...car doesn't get moisture under the dist cap in that location in a nice oily cloud, block doesn't collect gooey oil there.

Later, that location would make dist access difficult with the intake there (try dealing with it/dist service on an early PRV though (under the multi-piece intake)!) & they needed to figure out that wretched plastic oil trap box & gave the cars taller gearing/emissions cams to keep windage down/hot oil vapors/thu-flow PCV system with fresh air went away, which worked well on the old B18/B20s and made for fewer warm/cold/damp spots in the block for longevity/oil longevity on B18/B20 but wasn't as good for emissions.

The dist location & that plastic crankcase oil trap box is a sort of band-aid/revision to what was previously a better thought-out clean-slate design (for/of the era) of the old B18/B20s in some ways for emissions/the new aluminum x-flow head.


Refusal to buy any aftermarket or cats generally, on principle is probably logical & prudent.
Most are junk, exhaust all other possible causes first, as even if you by some miracle buy one of OE or better quality (doubtful such a thing exists in the aftermarket), if the engine's worn or out of tune, you could wreck something very expensive very easily.

Assuming the throttle position switch works/base idling is set right, no need to unplug the vac line to the mopar box, when the throttle is in the idling position, the mopar box ignores the manifold vacuum reading in that instance, basically.
Caveat: timing spec is A/C off/that base idling speed IIRC.

LH2.0 & 2.2 cars bump the idling speed up to ~900 with the A/C on. Timing might be more stable with the A/C dial turned @ the 900 speed, but I believe the spec is A/C off.

Lambda switching got a little higher resolution/more frequent with each version of LH-jet, idling speed got just a little slower, until you get to LH3.1; super lean burning, 540RPM idling speed! (some 5-speed 1990+ late cars, non-CA, non-EGR only).

But LH2.0 is like 775RPM + or -, LH2.2 725RPM, etc for base idling IIRC (check your book).
Base idle should be warm and there's the feeler gauge spec for when the throttle switch should close with a clean throttle body, technically.
Various o-rings and bits for the throttle body may be hard to find now, in practice, if the linkage is all in good shape, they mostly work fine.

I'd run the 87 t-stat too for most use.

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Old 08-10-2020, 03:59 PM   #17
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Go with a Walker cat. My magnaflow "failed smog" after only a couple years and the shop BS'd me saying they sent it in for analysis, and it a replacement was declined. I doubt he lifted a finger.


Also, on my 1991 740T, I run almost half a tank of E85 on stock injectors and ECU and it fixes my knock on hard accelleration
That's good to know about Walker and MagnaFlow!
I'll see where I can get some E85 gas.

Quote:
Originally Posted by Kjets On a Plane View Post
They sold an updated mopar box & harness for 81-87 cars. Not cheap in the day.
In practice, you can install the '88 mopar box & harness together in 85-87 cars.

Nice upgrade. Timing less wandery, has the sleeves on the pin for the plug installed OE (you're supposed to replace the sleeves if you unplug the box technically/keep the harness & box together per the volvo book).

The MAP sensor fails all together electrically and timing is full retarded/car won't pull a hill/overheats or spring can get weak/over-advances timing at cruise, failing NOX, yes.

Plug the vac line, don't disconnect, don't want a vac leak, make sure vac line isn't chafed/doesn't leak with your mity-vac.

If the dist gets oiled at the oil wick and oil is changed often, the dist probably isn't seized in the block in the AZ desert climate probably doesn't have a wobbly shaft. Penitrating oil between the dist/block to get the dist to move to set the timing and gummy gross oil is common in the PNW rainforest...that front corner of the intake side of the block is often filled with all sorts of goo in our climate (moisture trap, has the fan/cold damp air blowing on it here). Probably not even an issue where you are as long as the dist oil wick was oiled to keep the bushing from wearing out in it.

I refuse to buy any aftermarket or cats generally, on principle.
I checked the timing with the vac line plugged. The timing was at 11 degrees and was very steady. Once the car sat at temp for a bit, I did not notice any wandering.

I measured 14.5 +/- 0.5 in/Hg at the vac line with the MityVac. I figured there was a leak somewhere because I previously measured 16 in/Hg at the intake. The 90 degree elbow at the electronic box looks fine. The other end of the tube is a piece of rubber hose (not a 90 degree elbow) and was a little loose, so I put some Oetiker/European style hose clamps on it and made sure it is tight. I how measure between 15.5 and 16 in/Hg. I checked the timing after "fixing" the vacuum hose and it is now about 12 degrees.
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Old 08-10-2020, 04:02 PM   #18
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Quote:
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They sold an updated mopar box & harness for 81-87 cars. Not cheap in the day.
In practice, you can install the '88 mopar box & harness together in 85-87 cars.

Nice upgrade. Timing less wandery, has the sleeves on the pin for the plug installed OE (you're supposed to replace the sleeves if you unplug the box technically/keep the harness & box together per the volvo book).
Map sensor doesn't seem to fail on those.
Though I've had pretty good luck with the mopar box on the cool weather cars, seen more failures on CA cars.

The MAP sensor fails all together electrically and timing is full retarded/car won't pull a hill/overheats or spring can get weak/over-advances timing at cruise, failing NOX, yes.

Plug the vac line, don't disconnect, don't want a vac leak, make sure vac line isn't chafed/doesn't leak with your mity-vac.

If the dist gets oiled at the oil wick and oil is changed often, the dist probably isn't seized in the block in the AZ desert climate probably doesn't have a wobbly shaft. Penitrating oil between the dist/block to get the dist to move to set the timing and gummy gross oil is common in the PNW rainforest...that front corner of the intake side of the block is often filled with all sorts of goo in our climate (moisture trap, has the fan/cold damp air blowing on it here). Probably not even an issue where you are as long as the dist oil wick was oiled to keep the bushing from wearing out in it.

They kinda had it right with the B18/B20; dist out of the damp/in the middle of the nice warm block...car doesn't get moisture under the dist cap in that location in a nice oily cloud, block doesn't collect gooey oil there.

Later, that location would make dist access difficult with the intake there (try dealing with it/dist service on an early PRV though (under the multi-piece intake)!) & they needed to figure out that wretched plastic oil trap box & gave the cars taller gearing/emissions cams to keep windage down/hot oil vapors/thu-flow PCV system with fresh air went away, which worked well on the old B18/B20s and made for fewer warm/cold/damp spots in the block for longevity/oil longevity on B18/B20 but wasn't as good for emissions.

The dist location & that plastic crankcase oil trap box is a sort of band-aid/revision to what was previously a better thought-out clean-slate design (for/of the era) of the old B18/B20s in some ways for emissions/the new aluminum x-flow head.


Refusal to buy any aftermarket or cats generally, on principle is probably logical & prudent.
Most are junk, exhaust all other possible causes first, as even if you by some miracle buy one of OE or better quality (doubtful such a thing exists in the aftermarket), if the engine's worn or out of tune, you could wreck something very expensive very easily.

Assuming the throttle position switch works/base idling is set right, no need to unplug the vac line to the mopar box, when the throttle is in the idling position, the mopar box ignores the manifold vacuum reading in that instance, basically.
Caveat: timing spec is A/C off/that base idling speed IIRC.

LH2.0 & 2.2 cars bump the idling speed up to ~900 with the A/C on. Timing might be more stable with the A/C dial turned @ the 900 speed, but I believe the spec is A/C off.

Lambda switching got a little higher resolution/more frequent with each version of LH-jet, idling speed got just a little slower, until you get to LH3.1; super lean burning, 540RPM idling speed! (some 5-speed 1990+ late cars, non-CA, non-EGR only).

But LH2.0 is like 775RPM + or -, LH2.2 725RPM, etc for base idling IIRC (check your book).
Base idle should be warm and there's the feeler gauge spec for when the throttle switch should close with a clean throttle body, technically.
Various o-rings and bits for the throttle body may be hard to find now, in practice, if the linkage is all in good shape, they mostly work fine.

I'd run the 87 t-stat too for most use.
What would break?
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Old 08-10-2020, 04:18 PM   #19
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Cats can burn up / melt / honeycomb can break apart and clog if the engine burns oil or has an ignition miss/backfire etc.

If the engine's tip top, cat doesn't need to do a lot (still helps, especially somewhere really strict on all 3 numbers).

If it's not, don't buy a cat as a bandaid.
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Old 08-10-2020, 04:45 PM   #20
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Cats can burn up / melt / honeycomb can break apart and clog if the engine burns oil or has an ignition miss/backfire etc.

If the engine's tip top, cat doesn't need to do a lot (still helps, especially somewhere really strict on all 3 numbers).

If it's not, don't buy a cat as a bandaid.
Good to know.

I just did a water-decarb and will change the plugs once the engine cools off.
I changed the oil about 300 miles ago, but am not sure if I should change it since I did the decarb.
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Old 08-10-2020, 04:51 PM   #21
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^As it pertains to emissions, I only change oil if the car had a running problem/it has a bunch of gassy stinky ick in it & it's probably a good idea anyway at that point.

If it got driven on the highway/doesn't run rich or have known running issues or stink/reek of gas/gross hydrocarbons, changing it is unlikely to really help with emissions, especially if the engine isn't known to burn oil.

Furthermore, it doesn't help/make that much difference to change the oil on the volvos, as they're not prone to burning much oil (decel/intake valve stem seal puff letting off the throttle higher RPMs/vacuum, @ ~150K+miles, yes just a little bit on stick shift cars especially...decel not so much a thing with the auto-tragic/no lockup converter/always conservatively upshifting with mechanical controls on throttle lift-off) & the volvo SOHC doesn't have a PCV valve/through-flow crankcase vent system...just one-way out-flow thru that stupid mickey-mouse-band-aid plastic box while *trying* to cool/separate the oil out of the vapors, so the oil stinking of stinky gas doesn't make your emissions HC #s all *that* much worse, in all likelihood, and effects on NOX are likely tertiary/over time (built up carbon hot spots if anything).

Old honda that burns some oil with no hot & cold & damp spots in the well designed all-aluminum-alloy open deck crankcase/thru-flow PCV valve crankcase vent arrangement, dirty (hydro-carbon stinky) oil sure will, though, for example. Mostly HC #s more than NOX though. Granted, the oil doesn't so much get 'dirty' in the honda in the first place, just escapes past the rings/out the tailpipe! If it hits that sweet spot of still decent compression/tuned up perfect, you just never have to change it/keep adding (@ what point is smoke-less 2-stroke oil 'appropriate' pegging the charts for your white trash/OR incest-a-cada chainsaw logger award eligibility (guilty (no known in-breeding at least) )!

Granted, they make more smoke-less oils both to prevent knock & / or combust more completely.
Oil is fascinating that way, but if its to be burned, its applications are more slanted toward motorsports knock resistance in a 2-stroke or wankel, or high boost application where it's re-breathed partially than emissions/longevity, strictly speaking.

Diesel oils are great for detergents, but often lousy for smoke-less complete combustion or detonation resistance if burned to some extent; different goals.

For the summer in AZ for longevity, you can probably actually get away with a straight 30-weight (or even 40wt, though in theory the redblock has a lot of air around it/cooling system and thinner is often better for rings) without any cold starting issues & a block heater for no cold starts / less wear.

Oil really is amazing and has really difficult job to do. Way above me to know about what goes into it all.

Straight 30 wt on 20-30 degree damp/cold days here would be something like molasses / bubble gum to crank over.

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Old 08-10-2020, 06:55 PM   #22
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I failed my first test with like 800 nox over the max 750 or whatever it was. What I did (thanks to my fellow tbricker suggestions) was I plugged the yellow/white vacuum line going into the ignition control box that's on the passenger fender and I made extra sure my cat was warmed up by driving for like 30 minutes. I also left my car running while I waited for the test so the cat had no time to cool down. Also did an oil change because I had to anyway, not sure if it did anything. Second test I got almost 0 nox. Plugging the line made sure the car didn't advance timing when revving up, which apparently keeps the nox under control.
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Old 08-10-2020, 11:06 PM   #23
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I failed my first test with like 800 nox over the max 750 or whatever it was. What I did (thanks to my fellow tbricker suggestions) was I plugged the yellow/white vacuum line going into the ignition control box that's on the passenger fender and I made extra sure my cat was warmed up by driving for like 30 minutes. I also left my car running while I waited for the test so the cat had no time to cool down. Also did an oil change because I had to anyway, not sure if it did anything. Second test I got almost 0 nox. Plugging the line made sure the car didn't advance timing when revving up, which apparently keeps the nox under control.

Thanks for the tip. It's amazing it would make such a bid difference!
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Old 08-10-2020, 11:30 PM   #24
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Cooler more even temp combustion helps, whether with the aid of inert gas (EGR), or retarding the timing/cooling the points of ignition (spark plug, mostly) and having a bunch of the force that previously drove the piston down go out the exhaust valve/continue to combust gently thru the cat (with according power & economy loss / boiling the coolant on the exhaust side of the engine if retarding the timing excessively &/or possibly melting the cat/prematurely fatiguing all the exhaust hardware if leaving it that way ).

BB in the vac line; less timing at cruise/light load.
Retard initial advance to 9-10ish idling at correct speed/A/C off/whatever's allowable legally for a visual/prudent per the book/otherwise. (might have to reset base idling speed, timing affects it slightly)

Take your test.
What happens thereafter is anyone's guess.
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Old 08-11-2020, 12:15 AM   #25
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Cooler more even temp combustion helps, whether with the aid of inert gas (EGR), or retarding the timing/cooling the points of ignition (spark plug, mostly) and having a bunch of the force that previously drove the piston down go out the exhaust valve/continue to combust gently thru the cat (with according power & economy loss / boiling the coolant on the exhaust side of the engine if retarding the timing excessively &/or possibly melting the cat/prematurely fatiguing all the exhaust hardware if leaving it that way ).

BB in the vac line; less timing at cruise/light load.
Retard initial advance to 9-10ish idling at correct speed/A/C off/whatever's allowable legally for a visual/prudent per the book/otherwise. (might have to reset base idling speed, timing affects it slightly)

Take your test.
What happens thereafter is anyone's guess.
I did some searching, but don't see how to adjust the ignition timing. I did see where someone mentioned removing the dist, adjusting the rotor position, and reinstalling it. They also stated that a tooth either way resulted in the ignition being way off.

My car has mostly sat since March and ran ok, but not as smoothly as it did when I was driving every day. Today I fixed a small leak with the vac line that goes to the electronic box by the fender, did a water decarb, and replaced the spark plugs. It certainly seems to run more smoothly. I am probably going to replace the header pipe and then get it retested. Hopefully these maintenance items fix it.
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