First off I will say I have researched my problem to the fullest extent. Here it is.. since head gasket repairs Iam unable to get my scanmaster LBL reading to come off of 160, and Iac used to read high "78" now reads 0 after today.

So far today, adjusted valves again with engine off method.
Adjusted the valves 2 times with engine running.
Pulled fuel rail to check for a dripping injector.
Used vacuum gage, reads 20 in. vacuum with no needle fluctuate.
Checked plug wires to insure proper firing order.
Checked injector connectors to insure plugged into proper injector.
Installed new O2 sensors.

Any suggestions would be greatly appreciated, this car used to run perfect until this head gasket problem and Iam out of ideas.
1995 Z28

 

how is it not running right.

 

If you're showing 160 on the side with the head gasket replaced, and the IAC is driving shut, I'd be thinking huge vacuum leak somewhere.


What RPM is the car idling at??? If the LBL is stuck at 160, I believe that's interpreted at the computer is adding fuel to that side. Hence, unmetered air entering. IAC shutting to "0" tells me that the leak would be behind the TB somewhere.

 

Fastbird ... Wow ... Just wow

 

Thanks for the replies, car runs ok but definately notice power loss, maybe I will pull the intake back off, I tryed spray car cleaner around intake and no difference noted. Car seems to ilde normal at 900 rpm.

 

Just wanted to say did some more research and going to try to tighten the slip on tube some more from the number 1 cylinder on my header since its setting a code 44 lean conditon on that side, then definately search for a vacuum problem again even though gage reads 20 inches all the time. Hopefully I will be posting soon with my remedy.

 

Well 20" of vacuum is pretty good. I assume you're running a stock cam. If you're pulling that much then it may be something else. Have you given thought to a compression/leakdown test??

Reason I ask is that I had a somewhat similar experience recently. My black car would have the right side LTerms (RBL for you 94+ guys) dump to the bottom at 108, and my IAC would drive shut also. Turned out I had crushed ring lands in two cylinders.

Before you start thinking the worst, is the TB a stock or aftermarket?? Either way, try playing with the throttle stop to get the IAC working again, and watch the BL's while you do so. You may see a difference just from that. Reason being is that the IAC passages split when it hits the manifold, and there's two exit points, one in front of the #1 and #2 intake runners, essentially diverting air to both sides of the intake. If the IAC is shut, no air is getting through those passages, it's coming through the TB (or a leak, which you've ruled out). If it comes through the TB, it's not a guarantee that it's going to get "even" distribution so to say.

 

Stock cam and throttle body. Compression good on all the left cylinders 165-170. With defective ring land would I still have good compression ?