Idle to high around 2000rpms

[We Gone]

So I need some advice from the experts. I have a good friend here in Ga. who has a 91 P&P headers exhaust and tune If i had to guess 500 flywheel HP.

He can not get the idle down below 2000, This just started after the car sat for an extended time. I went over and helped check out the normal things such as vacuum or vacuum leaks none found. I hooked up my scanner and what I did find was a code 62, and the 02's never cross counted the stayed around 750-800 both right and left just a flat line??

He does run a % of race gas in it could that have burned up the 02's?
Will the 02's create this high idle issue?


Thanks Guys any help will be great.

[RussMcB]

Steve, are you sure there isn't a vacuum leak under he plenum?

When my (stock) ZR-1 had a 2,000 rpm idle, Marc H said (almost immediately) it was a vacuum leak, and he was right.

I'm not sure if fouled O2 sensors might cause high idle.

Good luck.

[Funracer]

I agree vacume leak. Last time I left a vacume hose off under the plenum
it idled at 2000. Pulled plenum again, reattached loose tube, prob solved.

[XfireZ51]

So I need some advice from the experts. I have a good friend here in Ga. who has a 91 P&P headers exhaust and tune If i had to guess 500 flywheel HP.

He can not get the idle down below 2000, This just started after the car sat for an extended time. I went over and helped check out the normal things such as vacuum or vacuum leaks none found. I hooked up my scanner and what I did find was a code 62, and the 02's never cross counted the stayed around 750-800 both right and left just a flat line??

He does run a % of race gas in it could that have burned up the 02's?
Will the 02's create this high idle issue?


Thanks Guys any help will be great.

IIRC a Code 62 is a left side O2 sensor running lean. Race gas could poison the O2. 750-800mv means rich. Could be ECM is trying to compensate. What are your IAC counts. I'll guess they're above 35.

[We Gone]

IIRC a Code 62 is a left side O2 sensor running lean. Race gas could poison the O2. 750-800mv means rich. Could be ECM is trying to compensate. What are your IAC counts. I'll guess they're above 35.

Thanks guys, The secondary vac system was in good shape and only cycled every 30+ sec. and than only a few burps. We did not want to pull the plenum just yet, may be my fault I got focused on the 02 readings. I to was thinking the ECM was trying to compensate, I don't remember the IAC counts and forgot to push the capture button.

We got to talking about car and stuff ;) I had not seen Mark in many years so we had a lot to catch up on. I'll make a trip back when I get more information may be a few weeks as its about a 100 drive one way. Was a great drive in the 93 for me!!! but the cam cover washer I replaced was still seeping just a bit.

I hope he does not mind but this is his beast...One great looking ZR-1

http://imagizer.imageshack.us/v2/800x600q90/907/a3Szvn.jpg

[RussMcB]

I agree. Very nice.

[We Gone]

Any other ideas or comments.

[GOLDCYLON]

Any other ideas or comments.


You have verified the MAP hose? Its sounds like an under hose plenium leak. The MAP would/should show an open fault as well

[A26B]

Option other than bad O2: Verify whether the 2000 rpm idle is vacuum leak or throttle related. Put a heavy book or piece of plywood over the air horn while running. Engine dies, it's throttle or IAC related, keeps running, it's vacuum.

[GOLDCYLON]

Option other than bad O2: Verify whether the 2000 rpm idle is vacuum leak or throttle related. Put a heavy book or piece of plywood over the air horn while running. Engine dies, it's throttle or IAC related, keeps running, it's vacuum.


Yep thats right Jerry anything that can block the intake I used a piece of cardboard it does the trick as well

[trobey]

Had the same problem you described a couple of months ago and I too thought it was oxygen sensor, but it was a vacuum leak. One on the vacuum hoses blew off, was quickly identified and replaced and ran like new. But it sure ran like crap with leak.

[We Gone]

Thanks guys

As I stated I'm not on site and we did not pull the plenum so your right we can not fully rule out a vac leak just could not hear one. The owner is also following this thread and I'm sure will try some of these ideas he is familiar with the ZR-1 and had this one over 15 years. Hope to get back up and see him in the next few weeks or after the next holidays.

[GOLDCYLON]

Thanks guys

As I stated I'm not on site and we did not pull the plenum so your right we can not fully rule out a vac leak just could not hear one. The owner is also following this thread and I'm sure will try some of these ideas he is familiar with the ZR-1 and had this one over 15 years. Hope to get back up and see him in the next few weeks or after the next holidays.


Let us know Steve

[edram454]

I just had work done at SGC and had my engine refinsihed and now my idle is at 1100rpm instead of its regular 800-900. I did have the plenum and injector house siamese ported and the injector bosses removed along with a fidanza flywheel and new corsa exhaust with long tube headers and no cats. the intake was ported by jeal and now reported by SGC. injector housing was ported by jeal at 34cm and now at 37.4cm. the coolant lines were removed from the plenun and capped off. Aaron said there was no vacuum leak and thought it could be the z industries chip. I dont believe that would be since it has been in this car for years. Car runs great except for the 1100 idle. I can live with this but I would rather not. what do you guys think? vacuum leak or throttle linkage since it was manipulated during the engine refinish. Any ideas would be appreciated.

ed ramos #3028

[XfireZ51]

I just had work done at SGC and had my engine refinsihed and now my idle is at 1100rpm instead of its regular 800-900. I did have the plenum and injector house siamese ported and the injector bosses removed along with a fidanza flywheel and new corsa exhaust with long tube headers and no cats. the intake was ported by jeal and now reported by SGC. injector housing was ported by jeal at 34cm and now at 37.4cm. the coolant lines were removed from the plenun and capped off. Aaron said there was no vacuum leak and thought it could be the z industries chip. I dont believe that would be since it has been in this car for years. Car runs great except for the 1100 idle. I can live with this but I would rather not. what do you guys think? vacuum leak or throttle linkage since it was manipulated during the engine refinish. Any ideas would be appreciated.

ed ramos #3028

I suspect they removed the throttle cable and disassembled the throttle body.
Did they re-set the Min Air throttle opening? Hopefully, removing the injector bosses left enough material to seal the injector.
Finally, are you saying they did this work and DIDN'T re-calibrate the tune????

[GOLDCYLON]

I just had work done at SGC and had my engine refinsihed and now my idle is at 1100rpm instead of its regular 800-900. I did have the plenum and injector house siamese ported and the injector bosses removed along with a fidanza flywheel and new corsa exhaust with long tube headers and no cats. the intake was ported by jeal and now reported by SGC. injector housing was ported by jeal at 34cm and now at 37.4cm. the coolant lines were removed from the plenun and capped off. Aaron said there was no vacuum leak and thought it could be the z industries chip. I dont believe that would be since it has been in this car for years. Car runs great except for the 1100 idle. I can live with this but I would rather not. what do you guys think? vacuum leak or throttle linkage since it was manipulated during the engine refinish. Any ideas would be appreciated.

ed ramos #3028

I suspect the PROM was not adjusted for the mods

[edram454]

no the prom was not adjusted yet. my car has the zimmer chip installed and had headers and ported intake already. I just had the injector housings re-ported and totally hogged out. I will eventually take it to have a dyno tune and burn a chip for it. the car runs very good and will probably run better with a good dyno tune. I had run out of time and just wanted my car back. I am taking care of a few things on the car to get it were it should be and will fine tune it later. he removed the intake injector bosses and ported the rest to the max and port matched to the head. I will send it back later and port- out the heads and then re-tune. I will take care of that idle speed later.

ed ramos #3028

[XfireZ51]

no the prom was not adjusted yet. my car has the zimmer chip installed and had headers and ported intake already. I just had the injector housings re-ported and totally hogged out. I will eventually take it to have a dyno tune and burn a chip for it. the car runs very good and will probably run better with a good dyno tune. I had run out of time and just wanted my car back. I am taking care of a few things on the car to get it were it should be and will fine tune it later. he removed the intake injector bosses and ported the rest to the max and port matched to the head. I will send it back later and port- out the heads and then re-tune. I will take care of that idle speed later.

ed ramos #3028

A "dyno tune" isn't going to do what is needed. At best, it optimizes for WOT ONLY. And although your Zimmer chip was meant for headers and porting, you're moving more air now and that needs to be adjusted for. In the meantime, enjoy the car.

[Pete]

If they didn't over port the injector bosses if they didn't miss any vacuum lines/hoses.
I think your issue is most likely your TB if they took it apart to powder coat or bore bigger.
If your idle with same chip was fine before should be same now.

I would start with TB
Pete