After the weekend before last at the track I started having problems with my car running lean at idle. Datamaster tells me it's lean and I eventually get DTC errors if I let it idle long enough. Tried a lot of things but haven't found the source of this false lean. Exhaust smells terrible at idle!

My question is has any one encounter this?

When I pump my brakes at idle the RPM raises 200 RPM and when I stop pumping the breaks the idle goes back down.

Not sure of the exact section this post should have been placed in.

Thanks in advance.

BC

 

What specific codes are you getting? I would assume DataMaster is showing you BLM's approaching 160 in Cell 16, correct? Sounds like there may be a vacuum leak. Does anything improve if you pull the vacuum hose for the brake booster off the intake manifold and block the connection off? What is the IAC doing when all this is happening?

 

Thanks Injuneer.

I will get you the answers to your specific questions soon. Right now I am at work.

Off the top of my head:

It runs lean at idle and low throttle.

At idle the LongTerm numbers are at 160 on both sides. As soon as the car goes into closed loop you can watch the ShortTerm numbers go up to 193 on both sides. If you wait long enough they will eventually set lean 02 errors on both side. One before the other.

I think there maybe a vacuum leak also but I can't seem to find. Gauge reads 10 but programmer said there should be around 12-15. I have sprayed carbon cleaner almost everywhere. Today one of my friends suggested that it may be a crack in the brake booster. I will try your test as soon as possible.

So far I have tried to.
Cleaning the MAF
Cleaning the EGR
Checking vacuum leaks using carbon cleaner
Cleaned IAC and reset
Reset PCM
Tightened intake bolts and header bolts.
Changing the Flange Collector gasket driver side. (Still thinks it has a small leak. I think I need something thicker then the stock gaskets.)

Car idles better for the most part but once the car
idles long enough and the short terms read very lean he car starts to
stumble I am pretty sure because of the extra gas
the pcm is commanding.

Thanks again.

 

Sounds like the brake booster to me if the vacuum leak / rpms seems to be affected by depressing the pedal. Plugging up the vac hose to the booster should show you the issue, be sure there's no slpits in the vac line too to the booster...cap off the nipple on the manifold..if the BLMs go back down then thats your problem.