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83 245t fails smog

A

adamdrives

Active member
Joined
Aug 9, 2010
Location
San Jose
Hey guys, looking for some help getting my 83 turbo wagon to pass smog. I've out a good amount of work into it, and drives fairly well, but is at the limit or exceeding all gasses on the dyno.

Relevant information:
  • New wire harness
  • new CPR
  • all sensors in head new
  • junkyard fuel distributor
  • cleaned injectors
  • new o2 sensor
  • valve clearance adjusted
  • all vac hoses replaced
  • frequency valve operational
  • about 100* drop after cat
  • just seafoamed and changed oil
  • it passed in 2018 with nothing too close to the limit

It's right at/over the the HC limit at idle, and slightly below loaded. CO is close to limit at idle, and a little high (0.6/1.0) loaded, according to my smog guy. NOx is very high, around 1800-2000 all the time, but much lower if you rev it up. According to my smog guy, its running rich at idle and leaning out (high NOx) loaded. He suspects the cat, but the temp test shows its good, not sure how meaningful that is.

I have good waveform from the oxygen sensor, it bounces between .2 and .8 or so and responds quickly if I make a big vac leak. I have components to make a fuel pressure test kit on the way, but I am wondering what adjustments I can make if the pressure is too high or too low.
 
"about 100* drop after cat"

Should be the opposite. Good Cat will raise the temp- not drop it. And the CO level that you have is not high. What is O2 %?
 
IPD_Smog_Check_List.jpg
 
Redwood Chair said:
What is the timing set at?

And what is the dwell?
Click to expand...

Timing is @ 12*, dwell fluctuates between 24-30

PCH said:
"about 100* drop after cat"

Should be the opposite. Good Cat will raise the temp- not drop it. And the CO level that you have is not high. What is O2 %?
Click to expand...

Ah, I had that backwards. I'll check the data sheet today at work for o2.
 
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I think the adjust to point is 42% but you need to confirm fuel pressure before you crank the CO screw.

Note on Philski's check list above that fuel is high on both lists and the cat is at the bottom of both.

I know, fuel pressure test equipment parts on order.

Buried in that long list of OZ documents is the GreenBook for CI.

https://greenbook-archive.s3.ap-sou...b8a4edbd129db03beaa92bb194b447765f18a7ded740e
 
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And BTW, 25MPH is HALF the load of the 15MPH portion.

CO is a good indicator of rich/lean.

I passed the ASE L1 Advanced Engine Performance class which is a prereq to become a smog guy here in CA. There were several questions about 5 gas analysis results. But it's not always very cut and dry to interpret the results.

As CO goes up (rich) NOX should go down.

I see high'ish CO and NOx and that make me lean towards kitty. I could be wrong.

Another thing I've been playing with is E85. I run a blend of about half a tank E85 in my 91 740T with a 16T cranked up. SOME E85 may bring emissions down.
 
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A TWC is a THREE WAY CAT. It lowers all THREE pollutants. You may be masking another issue, but when it comes down to getting your new registration sticker, or not, I may gamble with a $150 (installed) cheap aftermarket cat. It's worked for me more times than it hasn't.

That being said, this is on LH2.4 cars. On a LH2.2, or especially a Kjet, there is a lot more that can throw the mixture off and fail ya. GL.
 
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ZVOLV said:
A TWC is a THREE WAY CAT. It lowers all THREE pollutants. You may be masking another issue, but when it comes down to getting your new registration sticker, or not, I may gamble with a $150 (installed) cheap aftermarket cat. It's worked for me more times than it hasn't.

That being said, this is on LH2.4 cars. On a LH2.2, or especially a Kjet, there is a lot more that can throw the mixture off and fail ya. GL.
Click to expand...

There is no such thing as a $150/installed cheap aftermarket catalyst that will be CARB compliant.

To OP: it does sound like a cat will clean it up, everything else sounds okay. Inspect the Cat that is on the car currently, if it's an aftermarket catalyst already and has been on the car for more than 5 years it could be getting weak. If you do pull the trigger on replacing the cat, buy a Walker/Tenneco replacement. They clean up the best by far. Also, inspect the exhaust system for any leaks ahead of the catalyst. If there are any leaks, repair and re-test. Good Luck.
 
I've done a magnaflow and a Walker. I think it WAS about $150 installed. I may be wrong I forget. I prefer Walker at this point. Yes, both had CARB numbers.

PLEASE post back with the results. We want to hear that you passed!
 
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The cat looks original, on this car its part of the downpipe. It doesn't have any rattle or rusty welds like the later ones tend to. Right now I'm waiting for components for a fuel pressure test. Once I've confirmed that fuel is ok I'll look more into a potential cat issue.
 
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