Newbie with idle issues looking for help
Thread Starter
Teching In
Joined: May 2016
Posts: 8
Likes: 0
From: Southern California
Newbie with idle issues looking for help Hey guys, I just picked up an 01 z28. This is my first GM car and I'm still figuring how they operate. A little background info, the 4l60e blew for the prior owner, he took the engine out to re-gasket the motor and install with a level 2 trans and a circle d 3800 nitrous converter.
I bought the car with a bad idle issue when the engine is cold, I can barely get it to run unless I keep the RPMs up for a couple minutes before driving. The car smells like it's running rich. No check engine codes. I've been searching on this forum for advice but I'm hitting a dead end.
What I've done so far, I tried locating the grounds, the 2 on the radiator support are ok, the ones on both sides of the block are good. I managed to feel what I think was 1 (of the 3?) wire bolted to the back of driver head, I couldn't feel any grounds on the back of the passenger head but I might not have gotten my hand back far enough. The pcv tubing is all connected and appears to be brand new oem, it routes from front of intake to back of passenger and driver head. All the vacuum lines appear to be connected when I look at the diagram on the DS shock tower. I replaced the pcv valve within the hose but that didn't help. I hooked up a vacuum gauge and it read about 15/16 pounds. Unplugged the Iac, made no difference.
An interesting thing I noticed. If I disconnect the pcv valve and tube from the front of the intake and leave the pcv port unplugged, the engine idles great. If I plug the port with my finger or plug the pcv valve and hose back into the port it dies right away. Any advice you guys can offer would be greatly appreciated. This idle problem is driving me nuts.
I bought the car with a bad idle issue when the engine is cold, I can barely get it to run unless I keep the RPMs up for a couple minutes before driving. The car smells like it's running rich. No check engine codes. I've been searching on this forum for advice but I'm hitting a dead end.
What I've done so far, I tried locating the grounds, the 2 on the radiator support are ok, the ones on both sides of the block are good. I managed to feel what I think was 1 (of the 3?) wire bolted to the back of driver head, I couldn't feel any grounds on the back of the passenger head but I might not have gotten my hand back far enough. The pcv tubing is all connected and appears to be brand new oem, it routes from front of intake to back of passenger and driver head. All the vacuum lines appear to be connected when I look at the diagram on the DS shock tower. I replaced the pcv valve within the hose but that didn't help. I hooked up a vacuum gauge and it read about 15/16 pounds. Unplugged the Iac, made no difference.
An interesting thing I noticed. If I disconnect the pcv valve and tube from the front of the intake and leave the pcv port unplugged, the engine idles great. If I plug the port with my finger or plug the pcv valve and hose back into the port it dies right away. Any advice you guys can offer would be greatly appreciated. This idle problem is driving me nuts.
TECH Junkie
Joined: May 2012
Posts: 3,050
Likes: 715
From: Poplarville, MS
Check your Coolant temp sensor and Air Intake Temp Sensor. From what you have described, it sounds like it is running too rich. A wire at coolant sensor plug on my car broke and it would barely run and was very rich.
Thread Starter
Teching In
Joined: May 2016
Posts: 8
Likes: 0
From: Southern California
I'll check those out this weekend and post back. I just re-torqued my intake because the bolts were all loose but thst didn't help. Possible I have bad intake gaskets from running it with the intake lose. I'll pull the intake if the sensors check out good. My brother has a 98 z28 I can swap sensors with.
Thread Starter
Teching In
Joined: May 2016
Posts: 8
Likes: 0
From: Southern California
I've yet to take it for a test drive because the water pump went out too but I was able to confirm the IAC. It was stuck and wasn't opening. I cleaned it out with carb cleaner, bolted it back on and it started idling again perfectly.
