Rough idle with 89 Vette!
Thread Starter
4th Gear
Joined: May 2020
Posts: 4
Likes: 0
From: Panama City, Florida
Rough idle with 89 Vette!
I've got an 89 Corvette 6 speed with a bad idling issue.
When starting cold, it likes to surge from 900rpms to about 1700. If I drive it before it enters closed loop, it will rev to about 2100rpms while in neutral or pressing the clutch and will not go lower than 1700rpms while in gear cruising.
At first, I thought the IAC or TPS were the culprit. Both have been replaced and installed with the proper relearning/position procedures.
Throttle Body has been cleaned as well, and about 70% of vacuum hoses in the vehicle have been replaced.
O2 Sensor was replaced about 2 months ago and this problem is immediately following a head gasket repair project.
MAF sensor and relays are only a couple weeks old and fuel injectors were replaced with Bosch 3 22#s from Fuel Injector Connection during the head gasket process.
Unsure if it could be the cause but I also went ahead and did an AIR system delete - removed all the hoses and capped off the exhaust manifolds until I can get new headers.
I have a TunerCat chip in the ecm along with the appropriate software, and DataCat with the cable to read live data on the vehicle.
If anybody could please help, it'd be appreciated. I'm about at wits end!
When starting cold, it likes to surge from 900rpms to about 1700. If I drive it before it enters closed loop, it will rev to about 2100rpms while in neutral or pressing the clutch and will not go lower than 1700rpms while in gear cruising.
At first, I thought the IAC or TPS were the culprit. Both have been replaced and installed with the proper relearning/position procedures.
Throttle Body has been cleaned as well, and about 70% of vacuum hoses in the vehicle have been replaced.
O2 Sensor was replaced about 2 months ago and this problem is immediately following a head gasket repair project.
MAF sensor and relays are only a couple weeks old and fuel injectors were replaced with Bosch 3 22#s from Fuel Injector Connection during the head gasket process.
Unsure if it could be the cause but I also went ahead and did an AIR system delete - removed all the hoses and capped off the exhaust manifolds until I can get new headers.
I have a TunerCat chip in the ecm along with the appropriate software, and DataCat with the cable to read live data on the vehicle.
If anybody could please help, it'd be appreciated. I'm about at wits end!
Thread Starter
4th Gear
Joined: May 2020
Posts: 4
Likes: 0
From: Panama City, Florida
While hot and running the IAC reads 0 counts.. I tried an adjustment procedure outlined by another thread and was able to get the counts to 20 and stay there but then when I turned it off and cranked it back up, they were back to 0
Team Owner
Joined: Jul 2004
Posts: 28,473
Likes: 3,291
From: Hartford WI
It should hold steady at 20. I will Rev and let it settle back. If it can hold through a few revs that should be fine. When you Rev it goes up and settles down when you let off. When you shut off, it takes time to get back to closed loop.
