Hunting idle issue

[MuRCieLaGo]

I like the idea of resetting that IAC. Thanks a lot for your detailed answer, will continue my homework ASAP!

[XfireZ51]

Disconnecting the throttle cables necessitates re-doing the Min Air Adjustment.
That’s why I remove my plenum w throttle cables attached unless absolutely necessary otherwise.
The idle oscillation can also be a result of the throttle plate being open beyond the idle setting. Check ur TPS v and adjust if needed.

[Ccmano]

Originally Posted by XfireZ51

Disconnecting the throttle cables necessitates re-doing the Min Air Adjustment.
That’s why I remove my plenum w throttle cables attached unless absolutely necessary otherwise.
The idle oscillation can also be a result of the throttle plate being open beyond the idle setting. Check ur TPS v and adjust if needed.

Some good points, was the throttle position sensor removed or possibly knocked out of adjustment? Good to check the voltage.

With regard to a vacuum leak, while there are many possibilities, how much is your vacuum pump running with the ignition on but engine not running?
H

[secondchance]

Originally Posted by Ccmano

Some good points, was the throttle position sensor removed or possibly knocked out of adjustment? Good to check the voltage.

With regard to a vacuum leak, while there are many possibilities, how much is your vacuum pump running with the ignition on but engine not running?
H

If the pump stays quiet for 45 seconds, it's acceptable. However, this means good vacuum up to check valve. There could be other vacuum leak into intake.

[MuRCieLaGo]

Tonight I checked some stuff.

-No obvious leak.
-Vaccuum pump stays quiet for 13 seconds.
-TPS checked: 0.55V.
-Throttle cable isn't too tight, there's a slight slack in it when at rest.
-Tried to reset IAC, procedures don't seem to do anything.

Still no success...

When I let the car coast in 2nd gear I'm at 18 mph!

[Ccmano]

Originally Posted by MuRCieLaGo

Tonight I checked some stuff.

-No obvious leak.
-Vaccuum pump stays quiet for 13 seconds.
-TPS checked: 0.55V.
-Throttle cable isn't too tight, there's a slight slack in it when at rest.
-Tried to reset IAC, procedures don't seem to do anything.

Still no success...

When I let the car coast in 2nd gear I'm at 18 mph!

Ok, as Haibeck says (and I believe Hib too)... high idle is caused by a vacuum leak 99% of the time. In my opinion messing with the “min air adjustment” is a last resort and you need at least a Tech 1 scanner to do it. For your idle to change suddenly after a plenum pull still indicates a leak. The only way I would suspect the throttle body (requiring a min air adjustment) is if you wiped away the DAG sealing compound around the secondary throttle Plates thinking it was dirt build up. Another member here had fun with that one.

I would start here with Haibecks write up.

http://www.zr1specialist.com/HAT%20W...5%20Engine.pdf

H

[Hib Halverson]

If your secondary vacuum pump runs every 13 seconds you likely have a small leak somwhere in the SPT vacuum system.

However, as others have suggested if you have a vacuum leak which is causing the idle speed problem, it's not a leak in the SPT system causing the trouble.

If you can't find a leak, then maybe the TB is worn out and leaking.

In any event, fooling with minimum air to solve your problem is not a wise idea.

Marc's discussion of vac. leaks is outstanding. Like others suggest, start by reading that.

[XfireZ51]

Just to set the record straight, nobody is suggesting that Murcielago’s issue would be remedied by resetting the Min Air. Whenever addressing issues like this my approach is to first confirm that the basic settings and parameters are within spec. And that’s ALL I was recommending.
However, I would suggest getting a scantool (don’t need a Tech 1), to look at IAC COUNTS. You should have one anyway. It pays for itself many times over IMO.

[XfireZ51]

What was the coolant temp that video was shot at? Just after startup?

[MuRCieLaGo]

So I guess I'll go through that pdf, seems to be fairly simple! I bought a Bluetooth adapter but it doesn't work in real time, I get a reading every 3 seconds when I'm lucky (frustrating). I might remove that Secondary Vaccuum System (and sending my chip to Marc Haibeck)...

Video was taken at the startup after disconnecting the battery. Temperature was just starting to rise on the needle (10 minutes after I started the car).

PS: When I removed the plenum, there was still some pressure in the coolant system. I know it basically filled the hole that goes to #6 cylinder. The car had a lot of white smoke for maybe 15 minutes at idle. Not sure if it could have affected something.

I can't thank you enough for your help guys. I love the ZR-1 community, so friendly.