I have been having this nasty stumbling/missing problem with my car after the engine warms up. I have replaced the O2 sensor so I don't think that was the problem.The car seams to cycle this stumble, another words its not constant. The car has thrown a code 45,42 & 43 in the last 2 weeks, but once the codes are cleared it takes a long time before any come up again.According to my hanes manual some of the sensors that can be at fault with these codes are the EGR,Knock sensor,Ignition module.I had the car to an auto Mechanic last week but they could't be sure what was causing this problem (No codes being thrown by the computer that day. The mechanic had a feeling it might be the EGR. What do you guys think?

------------------
1990 Iroc convertible,305 tpi,Black with black leather interior,lowered,Taylor 8mm wires,K&N's

 

I've had more trouble with TPS (Throttle Position Switches). A TPS is nothing but a sliding potentiometer and can cause problems because of wear to the resistive surface. Uneven resistance will cause drivability problems but not cause the ECM to flag a code.

A bad EGR will certainly cause pinging as will a defective Knock Sensor. Be sure to check for carbon deposits in the EGR passages. If the passages are restricted, you will get all of the symptoms of a bad EGR valve even though the valve itself is OK.

But, in your case, I'd take a look at the TPS and see if it's OK even though the fault code isn't showing.

 

Before i got it replaced (e-test) the EGR valve on my car was not working at all. It was completely clogged up with carbon, but the car ran perfectly.

------------------
1985 305 Z28
White w/ Grey ground effects
Red interior
K&N Chrome Element and Filter
Flowmaster 80 series muffler
Aftermarket High-Flow Cat
Chrome Edelbrock Valve Covers

 

if the car has a bad EGR the car should run bad all the time..

my guess is you have a vacuum leak that is appears to be worse when the engine is running because it's more exaggerated on a hot engine..

EGR symptoms would give you things like:
<ul>[*]rough idle because it's hanging open[*]rough idle or 'surging' on the freeway because it's hanging open[*]smooth acceleration[*]'surging' or smooth acceleration under part throttle, could be either depending how bad it is[*]could be throwing a code[/list]
my car had a bad EGR and it didn't even throw any codes.. it was probably still within factory spec but the car ran horribly..

------------------
Webmaster: www.IROC-Z.org

[This message has been edited by ColinOpseth (edited July 11, 2001).]