Another low idle thread...
Thread Starter
Teching In
Joined: Feb 2013
Posts: 37
Likes: 0
From: Pennsylvania
Another low idle thread... Ok... I've been searching for a fix for this for over a year now. Still have no clue what it could be. Before you ask, yes I've searched other threads/forums. Hundreds of them. Every single one dies before they find the problem. At this point I'm just looking for opinions on where the problem could be coming from.
My car runs perfect until it gets up to operating temp. Once it gets there it starts to idle low (about 400-500 RPM) and idle rough like its missing. On rare occasions it surges too. Usually only after not running for awhile. It runs fine when I'm driving, the problem just exists just at idle.
My car is a 94 Z28. 42,000 miles. LT1 A4. All stock with the exception of an adjustable borla cat-back exhaust. Cat is gutted. I've replaced: Spark plugs, Spark plug wires, O2 sensors, Air filter, Battery, and the fuel filter. Cleaned all the sensors I could and tested them as well. 99.9% sure the opti is good. EGR valve is good. Checked, checked and checked again for vacuum leaks. Fuel pressure is fine. No codes what so ever. I've run fuel injector cleaner through it too.
A few more side notes...stick with me...
Recently changed the spark plugs and they were soaked with gas. I have an oil leak somewhere. Nothing major. Never any puddles but it is all over underneath. When i let of the gas the exhaust pops..not sure if any of that really matters one way or another.
I'm sure I'm forgetting something along the way but if you made it all the way through that you're awesome lol. Thanks for any and all advice..Really appreciate it!!
My car runs perfect until it gets up to operating temp. Once it gets there it starts to idle low (about 400-500 RPM) and idle rough like its missing. On rare occasions it surges too. Usually only after not running for awhile. It runs fine when I'm driving, the problem just exists just at idle.
My car is a 94 Z28. 42,000 miles. LT1 A4. All stock with the exception of an adjustable borla cat-back exhaust. Cat is gutted. I've replaced: Spark plugs, Spark plug wires, O2 sensors, Air filter, Battery, and the fuel filter. Cleaned all the sensors I could and tested them as well. 99.9% sure the opti is good. EGR valve is good. Checked, checked and checked again for vacuum leaks. Fuel pressure is fine. No codes what so ever. I've run fuel injector cleaner through it too.
A few more side notes...stick with me...
Recently changed the spark plugs and they were soaked with gas. I have an oil leak somewhere. Nothing major. Never any puddles but it is all over underneath. When i let of the gas the exhaust pops..not sure if any of that really matters one way or another.
I'm sure I'm forgetting something along the way but if you made it all the way through that you're awesome lol. Thanks for any and all advice..Really appreciate it!!
Where is the oil coming from? Did it get on the opti? Oil on the O2's can cause issues.....I'd look into that. Could be the dreaded back of the intake oil leak. Who scanned it and with what scanner? I would think there would be codes of some sort with that issue.
Thread Starter
Teching In
Joined: Feb 2013
Posts: 37
Likes: 0
From: Pennsylvania
No lights/codes. Not quite sure where its leaking from. Its not much but i will be looking into it. Oil level is about where it should be and isnt discolored or anything. The O2's are a couple months old. They're still clean.
Thread Starter
Teching In
Joined: Feb 2013
Posts: 37
Likes: 0
From: Pennsylvania
The ICM was checked too. I guess it could be failing when it gets warm but would that give me a rough idle/miss? Kind of a long shot here but My exhaust has adjustable plates and i have the wide open one in now. So its pretty much a straight pipe. With that plus the gutted cat give me too much flow for a stock car? Still has stock manifolds on it.
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On The Tree
Joined: Jul 2006
Posts: 177
Likes: 0
From: Keego Harbor, Michigan
Is your car on a stock tune? Your symptoms to me, indicate a car running rich. If you have anyone local that tunes LT1's well i would have them look at it. if not i would mail it into of the mail order tuners.
On The Tree
Joined: Jul 2006
Posts: 177
Likes: 0
From: Keego Harbor, Michigan
TECH Veteran
Joined: Apr 2008
Posts: 4,985
Likes: 112
san tool or just look at it?
you should not have to adjust the stop screw on TB if this problem was not there before....they don't "back out" on their own
did you scan or use a volt meter to check IAC volts?, you should if you have not
TECH Addict
Joined: Dec 2010
Posts: 2,610
Likes: 4
From: Maricopa, AZ
Ok... I've been searching for a fix for this for over a year now. Still have no clue what it could be. Before you ask, yes I've searched other threads/forums. Hundreds of them. Every single one dies before they find the problem. At this point I'm just looking for opinions on where the problem could be coming from.
My car runs perfect until it gets up to operating temp. Once it gets there it starts to idle low (about 400-500 RPM) and idle rough like its missing. On rare occasions it surges too. Usually only after not running for awhile. It runs fine when I'm driving, the problem just exists just at idle.
My car is a 94 Z28. 42,000 miles. LT1 A4. All stock with the exception of an adjustable borla cat-back exhaust. Cat is gutted. I've replaced: Spark plugs, Spark plug wires, O2 sensors, Air filter, Battery, and the fuel filter. Cleaned all the sensors I could and tested them as well. 99.9% sure the opti is good. EGR valve is good. Checked, checked and checked again for vacuum leaks. Fuel pressure is fine. No codes what so ever. I've run fuel injector cleaner through it too.
A few more side notes...stick with me...
Recently changed the spark plugs and they were soaked with gas. I have an oil leak somewhere. Nothing major. Never any puddles but it is all over underneath. When i let of the gas the exhaust pops..not sure if any of that really matters one way or another.
I'm sure I'm forgetting something along the way but if you made it all the way through that you're awesome lol. Thanks for any and all advice..Really appreciate it!!
My car runs perfect until it gets up to operating temp. Once it gets there it starts to idle low (about 400-500 RPM) and idle rough like its missing. On rare occasions it surges too. Usually only after not running for awhile. It runs fine when I'm driving, the problem just exists just at idle.
My car is a 94 Z28. 42,000 miles. LT1 A4. All stock with the exception of an adjustable borla cat-back exhaust. Cat is gutted. I've replaced: Spark plugs, Spark plug wires, O2 sensors, Air filter, Battery, and the fuel filter. Cleaned all the sensors I could and tested them as well. 99.9% sure the opti is good. EGR valve is good. Checked, checked and checked again for vacuum leaks. Fuel pressure is fine. No codes what so ever. I've run fuel injector cleaner through it too.
A few more side notes...stick with me...
Recently changed the spark plugs and they were soaked with gas. I have an oil leak somewhere. Nothing major. Never any puddles but it is all over underneath. When i let of the gas the exhaust pops..not sure if any of that really matters one way or another.
I'm sure I'm forgetting something along the way but if you made it all the way through that you're awesome lol. Thanks for any and all advice..Really appreciate it!!