94 q45 stalling when warm

[SidewaysSlider]

OK. I have a 1994 q45 (bone stock)... I just bought about a month ago. i replaced both knock sensors and a bad fuel injector. Now she starts up fine and idles fine for a while. Once the car is at normal operating temperature, she'll start to stutter a bit then the revs will start to drop and then eventually die out. As she is stuttering and the revs drop, the exhaust will smoke(whitish). From then, I'll have a hard time starting her and keeping her to idle. I'll have to press the gas to keep it from dying out. Any advise would be greatly appreciated!! Thanx! oh....the car has 76,xxx miles on it.

[Q_SHIP]

Do you hear the fuel pump humming? I have heard cases of pumps failing after they heat up. The pump may be so clogged it's heating up the pump more than it should.

Turn the key tu the "ON" Position and listen for a hum in the back seat area. If it's really bad, it can be heard with the car running.

Just a thought.

[Q45tech]

Have the IAC duty cycle checked.

When cold started what does rpm rise to [2000 rpm-1500 rpm?]............what is position of coolant temp needle when problem starts?

Probably just needs a serious degunking in intake, plenum and IAC.

Does PCV valve work? Rattle when shaken?

[bruce.weiland]

May not be close, but.... I had a problem with one of my Q's under warranty. I really can't recall if it was the 91 or the 95.

It would start and run fine, but after it warmed up it ran very roughly at lower rpm. If I was driving freeway speed it was not a problem. Once the rough running started, if I turned it off, I could not restart it. Had the smoking problem too.

They had the car for about a week and a half total. They changed out three different types of injectors and thought they had the problem solved. It was warmed up when I picked up the car, they had it "fixed" for a day, and before I drove off the lot, it did it again.

They finally solved the problem. It was a warped fuel manifold. As the car warmed up the fuel rail (please correct me on that Q45tech if that is the wrong term) that supplied the injectors would warp enough with the heat to cause the problem. Once they changed out that part the problem never recured.

Just one more thing to check.

Bruce

[SidewaysSlider]

when i start the car cold, the revs go to about 1300-1500 rpms then slowly come down to about 850-750rpms. When i replaced the knock sensors and fuel injectors, i cleaned the IAC and the plenum. How do you check the IAC duty cycle?? Thanks for the responses guys. keep'um coming!.

[maxnix]

How do you check the IAC duty cycle??

I believe with a scope. Search for Q45tech's posts on the subject, IAC.