3k rpm idle until stopped. New IAC and TPS
01-06-2015, 02:46 PM
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Staging Lane
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3k rpm idle until stopped. New IAC and TPS My car, 2000 ls1 m6 with a cam, will stick to 3k rpm while driving. When I come to a stop it will slowly drop down to the proper idle. I threw a code for tps and iac. I replaced both and it still does it. When the car is idling normally, I can unplug the iac and the car will no longer have this sticking idle when driving around. What could cause this? The car has been driven 10k miles after swap, and this just recently happened.
Last edited by LSX Man; 01-06-2015 at 04:01 PM.
01-12-2015, 01:23 PM
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Staging Lane
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The car is a 1991 camaro, with a ls1 and t56 out of a 2000 trans am. Car has 236/238 601 cam along with Longtube headers. I had a mail order tune from vengeance racing that has worked great for 9,000 miles. This problem is new. I have a new tps sensor, iac, along with a new battery. The car keeps throwing a code for the tps. I even changed it with another new tps and had the same problem. When Iac is unplugged the problem goes away, even swapped iac sensors out as well with another new one.
I checked for vacumn leaks across the board with no luck, all lines seem good. I also disconnected the battery over night to reset the computer with no luck.
I am truly lost at this point. Any advice would be great!
I checked for vacumn leaks across the board with no luck, all lines seem good. I also disconnected the battery over night to reset the computer with no luck.
I am truly lost at this point. Any advice would be great!
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01-30-2015, 02:05 PM
#9
Since this was a swap, it's possible something in the wiring harness came loose? You might try to check the connections for the IAC plug from the harness with a volt meter. Do you know what code it threw? The TPC and IAC come out of the loom together so it may be a wiring issue.
But, it does sound like you're getting a cruise control effect from having the IAC at full open when cruising around. When you disconnect and the cruise control effect goes away, have you taken then IAC out to see its stopper position?
If it's fully closed when disconnected, then that's why it idles correctly (it opens up when cold and slowly steps down as the car warms up and the airflow requirements lax). That would explain the problem if the IAC remains open. So, when you plug it in, if there is a short, the IAC may open fully allowing a lot of air into the motor, bypassing the throttle blade.
I'd check the wiring harness for any problems. And probably just run the IAC with the stopper set around a quarter open for now unplugged. You might have some cold start issues, but around town it'll be fine. Your IAC motor has 310 steps per the PCM. Hot, you want it around 40-70 with the cam. So that's 40 steps from closed. 310 = fully open.
But, it does sound like you're getting a cruise control effect from having the IAC at full open when cruising around. When you disconnect and the cruise control effect goes away, have you taken then IAC out to see its stopper position?
If it's fully closed when disconnected, then that's why it idles correctly (it opens up when cold and slowly steps down as the car warms up and the airflow requirements lax). That would explain the problem if the IAC remains open. So, when you plug it in, if there is a short, the IAC may open fully allowing a lot of air into the motor, bypassing the throttle blade.
I'd check the wiring harness for any problems. And probably just run the IAC with the stopper set around a quarter open for now unplugged. You might have some cold start issues, but around town it'll be fine. Your IAC motor has 310 steps per the PCM. Hot, you want it around 40-70 with the cam. So that's 40 steps from closed. 310 = fully open.
