Idle Issues...
04-10-2008, 07:15 PM
#1
Launching!
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Idle Issues... Car details:
2002 Z28. full exhaust, stock computer tune, ported throttle body (not radical, worked fine on car it came off of), 80k miles on motor. no emissions crap. smooth bellows. manual. brand new plugs, wires, and oil.
What it does:
It sounds like the typical hanging idle problem that other people have had. It idles at 1500 when you're moving but, drops to 1000 only when fully stopped.
What we tried:
Following the recommendations from the mighty search button we had the car checked for vacuum leaks and found none. Thought it might be a bad IAC, replaced that and it made it WORSE (idled at 2500 instead).
What else might be wrong with the car:
she's had a hard life. Theres RTV around the oil pan, so who knows what that's masking and what ELSE might be wrong with it. The car has a lot of water coming out of the exhaust as well and it looks like a cold morning start with the water vapor and all, only in the afternoon with 70* weather. Also needs a new clutch pretty bad.
So does anyone have any ideas about how to fix the idle on the car? it gets shitty MPG for being so stock and all the other issues might be pointing to a larger problem, so i'm actually thinking about getting rid of it before the whole thing falls apart. THANKS!
2002 Z28. full exhaust, stock computer tune, ported throttle body (not radical, worked fine on car it came off of), 80k miles on motor. no emissions crap. smooth bellows. manual. brand new plugs, wires, and oil.
What it does:
It sounds like the typical hanging idle problem that other people have had. It idles at 1500 when you're moving but, drops to 1000 only when fully stopped.
What we tried:
Following the recommendations from the mighty search button we had the car checked for vacuum leaks and found none. Thought it might be a bad IAC, replaced that and it made it WORSE (idled at 2500 instead).
What else might be wrong with the car:
she's had a hard life. Theres RTV around the oil pan, so who knows what that's masking and what ELSE might be wrong with it. The car has a lot of water coming out of the exhaust as well and it looks like a cold morning start with the water vapor and all, only in the afternoon with 70* weather. Also needs a new clutch pretty bad.
So does anyone have any ideas about how to fix the idle on the car? it gets shitty MPG for being so stock and all the other issues might be pointing to a larger problem, so i'm actually thinking about getting rid of it before the whole thing falls apart. THANKS!
04-12-2008, 08:41 PM
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TECH Apprentice
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Do you know anyone who knows how to tune? You really need to know where the IAC piston is in relationship to the TB blade. I'm not a tuner, but your new IAC making things worse would at least be a good place to START troubleshooting. If you know someone with a laptop & tuning software, or someone with a VERY capable diagnostics scan tool, you might want to take a look at IAC step, and throttle blade position (may not be opening far enough at idle, causing IAC piston to "run out of adjustment travel). At operating temp, the IAC shouldn't be open much more than 25% or so.
After that, I'd look at timing, and/or possible fuel pressure problems......wish I had more to offer, but I'm behind the curve as far as diagnosing EFI sensor problems.
After that, I'd look at timing, and/or possible fuel pressure problems......wish I had more to offer, but I'm behind the curve as far as diagnosing EFI sensor problems.
04-14-2008, 03:51 PM
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Launching!
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yah, we were thinking of having the car tuned as well... think those other issues its having might affect the idle, etc? apparently after a bit of driving after the new IAC, the stopped idle lowered to 850... so it helped a little bit... the car's still not right though.. It's just odd to me that a car thats so close to stock would have such large issues... :/
04-14-2008, 08:24 PM
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This is just a thought , but by any chance did the other person who had that throttle body drill a hole in the butterfly ? That would cause a high idle on a stock engine .
