89 tpi rough idle. suggestions?
Thread Starter
Intermediate
Joined: Apr 2008
Posts: 44
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89 tpi rough idle. suggestions?
i have a 89 drop with 105,ooo miles and runs STRONG. stock except for k&n air filter, high perf. coil, high flow cat and dual flowmasters. after it warms up, there is a miss. (its probably there the whole time but not as noticeable) the only times you'll notice it is when youre at a light and the rpms fluctuate (from 5oo to 7oo), sort of pulsating. any suggestions? id appreciate it!
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Fluctuating idle sounds like maybe a vacuum leak or a dirty IAC pintel & bore.
First check for any stored trouble codes.
Check manifold vacuum and inspect the hoses for cracks.
Remove the IAC motor and clean the pintel & bore; method on my site.
Also clean the TB bore & plates with TB cleaner, not carb cleaner.
Put a timing light onto each wire to see if the miss corresponds to a miss on one of the wires.
First check for any stored trouble codes.
Check manifold vacuum and inspect the hoses for cracks.
Remove the IAC motor and clean the pintel & bore; method on my site.
Also clean the TB bore & plates with TB cleaner, not carb cleaner.
Put a timing light onto each wire to see if the miss corresponds to a miss on one of the wires.
Le Mans Master
Joined: Sep 2006
Posts: 6,050
Likes: 147
From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
fluctuating idle
I just had something similar. I got a check engine light, and it gave a code 33. That is the MAF. I unplugged the maf, re installed it, tapped on the MAF power relay, got back in, started it up, and it was still there. turned the car off, started it again, tapped on the MAF, and the check engine light was out. drove about 2 miles, it was back on again. hunting idle and check engine light.
I unplugged the MAF relay, plugged it back in after inspecting the relay blades, and it stayed out. hasn't come back on since.
I had a hunting idle about 2 years ago, and I unplugged the ignition module over on the right side by the heater. the engine stabilized, and gave a code for the ignition control module.
I changed the module, disconnected the battery for 2 minutes, and it never came back till last week when the MAF 33 code came on.
update.......
I got the check engine light again today, and same thing. hunting idle. check engine light. code 33. I changed the MAF power relay because when I shut the car off and got gas, when I started the engine, it was all normal.
I did notice on the freeway, when the light came on, the gas pedal was like a fuel pump switch, either on and accelerating, or coasting.
hope it helps
I unplugged the MAF relay, plugged it back in after inspecting the relay blades, and it stayed out. hasn't come back on since.
I had a hunting idle about 2 years ago, and I unplugged the ignition module over on the right side by the heater. the engine stabilized, and gave a code for the ignition control module.
I changed the module, disconnected the battery for 2 minutes, and it never came back till last week when the MAF 33 code came on.
update.......
I got the check engine light again today, and same thing. hunting idle. check engine light. code 33. I changed the MAF power relay because when I shut the car off and got gas, when I started the engine, it was all normal.
I did notice on the freeway, when the light came on, the gas pedal was like a fuel pump switch, either on and accelerating, or coasting.
hope it helps
Last edited by coupeguy2001; May 1, 2008 at 11:19 PM. Reason: info
Thread Starter
Intermediate
Joined: Apr 2008
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ive been hearing the word "injectors" alot, so i tested the connections to each injector and the ohms were similar, so the spark is fine, but does anyone know how to test the injectors? ? ? (p.s. im going out with a can of wd40 to do a more thorough vaccuum check right now)
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Joined: Oct 2007
Posts: 6,795
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From: So. Cal.
2025 C7 of the Year Finalist- Unmodified
2024 C7 of the Year Finalist - Unmodified
2023 C7 of the Year Finalist - Unmodified
miss
Runs fine cold in open loop. After 2 minutes goes to closed loop. Misses in closed loop. If this is the case, its injectors
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