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BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

About 2 days ago the car started running like shit cold, warm, hot doesn't matter. Did not want to idle. It felt like it was running lean so I richened it and the car ran better but still didn't really have any balls unless I floored it and then it cleared up and ran great, but at least it would idle.

Today I got a day off so I started poking around and found that something had flown up and disconnected the O2 sensor. So I put my gastester on the car and got the mixture adjusted to a 1.7% CO reading and then hooked the O2 sensor up.

Car runs worse. I disconnect the O2 sensor and it does the same thing as before, it will run like its either flooding or starving at anything between idle and full throttle. It kind of does the same thing with the o2 sensor hooked up too, but actually has less power.

It seems like the problem is that the O2 sensor has been damaged and needs to be replaced. My question is, should it make that big of a difference? Shouldn't the car run fairly well without the o2 sensor? From my understanding, it only allows tweaking to the mixture via the frequency valve and that this tweaking is by no means instantaneous. With it disconnected it should be defaulting to a 50/50 duty cycle, right?

Am I missing something? Is there something else I should look for or is the O2 sensor likely the entire problem?
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1980 924 NA
1982 931

xanderdeg · Posted: Thu Mar 07, 2013 3:44 pm Post subject:

Check for vacuum leaks!

kcoyle · Joined: 15 Jan 2011 Posts: 712 Location: Long Island, NY

DITC connection if it's the turbo car?
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1982 931- Stock with MBC at 8psi

Relax, all right? My old man is a television repairman, he's got this ultimate set of tools. I can fix it.

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

Sorry, NA car. Vacuum leak is possible... I did screw the adjustment screw all the way in and idle only fell to 1k.
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1980 924 NA
1982 931

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Definitely sounds like a major vac leak. Your mixture is probably all fubar'd now.
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erstwhile owner of just about every 924 variant ever made

staticsan · Joined: 19 Jan 2009 Posts: 450 Location: Sydney, Australia

I can confirm that a vacuum leak will destroy the car's ability to idle. That happened to mine. It was tricky keeping my foot on both the brake and the accelarator so it wouldn't die at lights!

Wade.
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'82 British NA - Which I think I've been very lucky with!

pmcaya2 · Joined: 24 Nov 2005 Posts: 191 Location: Scio, NY USA

Since this was a sudden drop in performance, Check the air handling ducting between the fuel distributor and intake - the injection system depends on a good vacuum.to lift the intake plate.

There's another thing to check: Timing alignment between the cam mark, crank and distributor. I experienced a drop in performance and checked everything twice. When I removed the timing belt cover, I found a dead mouse trapped in the housing - it slipped the timing 3 or 4 cogs - it ran , but not well. I thought that this was very unusual until a friend told me that the same thing happened on his VW engine. This can occur when an engine isn't run much in winter. Ice can also cause the problem - its worth checking. - Peter

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

So I check the mechanical timing and found that it was off just slightly due to the tensioner moving the crankshaft pulley when applying tension. Took care of that even though I doubt it was causing much of an issue. I also adjusted the ignition timing to about 3 degrees advanced, had it at 10 degrees advanced before. hooked up the mity vac and checked the vacuum. It floated from 12 - 15 psi indicating that it was either running rich or lean. So I adjusted the A/F ratio until the vacuum held steady at 16 psi.

I sprayed down every thing in the engine bay with brake cleaner trying to find a leak, and found nothing.

Car runs alot better when warm, still not perfect. Runs like total ass when cold. Idles great anytime.

Going to recheck my cold and hot fuel pressures and my compression Wednesday (my next day off).

Any other ideas? I haven't replaced the O2 sesor yet, but I really don't think it has anything to do with my problem.
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1980 924 NA
1982 931

BionicBalls · Joined: 05 Jan 2009 Posts: 642 Location: Charlotte, NC

Checked my fuel pressures:

Cold: 40 psi
Hot: 54 psi
System: 72 psi

Obviously a problem with the WUR. I took it apart and cleaned it all out and put it back together. Didn't see anything clogged, and the heater element was working properly.

Retested this morning and got 10 psi at about 40 degrees. It rose steady to 54 and held. Car is running like a champ again. Not sure what caused the WUR to act up so all of a sudden. Going to change the filter tomorrow just to be on the safe side.
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1980 924 NA
1982 931