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Q. for those with manual transmission

moustacio

New member
Joined
Mar 10, 2012
Location
Colorado
Hey all,

Quick question that should apply to anyone with a manual transmission:

While driving and then putting the car in neutral, does your vacuum reading fluctuate slightly? Also, same scenario, does your rpm's drop straight to idle speed and stay, or is there a slight fluctuation there as well?

Thanks for any input.

For reference, 1988 745 turbo with m46
 
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These cars don't usually idle perfectly although it's not impossible. I would say some fluctuation is normal and yes it does drop to idle speed in neutral. Since your also in Colorado the high altitude could make it tougher to get a perfectly smooth idle.
 
I'd expect idle to move up and down by 50-100rpm in normal operation. Wouldn't worry much about it as long as it's not really hunting.
 
Hey thank you for the replies and assurance.

Was having bad rpm jumps and vacuum loss upon shifting to neutral before fixing some fuel issues. Glad to hear this is "normal" behavior after fixing my fuel issues.

And I actual get pretty steady idle when the car is just running, like waiting for it to warm up. Last time I had a timing light on it I had around max +/- 100 rpm swing.

Thanks again guys.
 
MMO in Gas

Hi everyone,

Another question for y'all:
So I filled up and added Marvel Mystery Oil to the gas (around 6 ounces for around 16 gallons of gasoline) and now I don't have any of the symptoms in my first post. The symptoms stopped after 20 miles or so of driving with the mix.

Questions are: does this sound like the MMO is lubricating worn fuel pump(s)? Something with the injectors? Something else?

I've used Techron and Lucus upper cylinder cleaner in the gas somewhat regularly but never got these results.

Any input is much appreciated and hopefully this might help someone else.
 
MMO is good stuff. You probably just needed something like that to clean the injectors better than the Techron. I used to use the Techron for a long time and it always took a few tanks to notice a difference. The Lucas worked better for me and MMO was probably the right additive at the right time for your situation.
 
You likely just need to have your injectors cleaned. MMO is good (Lucas is similar) to help limp some older injectors along, but after a while even that won't help. Pulling the injectors is easy and most injectors clean up fine.

I've done this a number of times over the years on different cars. I use Dr. Injector local to me. Not cheap, but cures all of the drivability issues associated with old gunky injectors. I also use quality fuel (no Arco).
 
Hey thank you much for the replies.

I will continue to run the MMO in the gas until I get around to cleaning the injectors. Or swapping in new high impedance injectors after bypassing the resistor pack. I'll update with any changes. And yes, ever since I've had the car it's either shell or exon/mobile fuel.

Thanks again everyone
 
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