sporadic idle issue
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New User
Joined: May 2018
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From: Idaho
sporadic idle issue
Im having a problem with sporadic idle. On cold start she fires right up and runs great until I touch the throttle. The rpms shoot up pretty high and won't come back down. Sometimes it will chug and stall nearly to the point of dying then it recovers and runs fine for a few minutes. I checked my IAC but it appears to be fine. I plan to hit it with some carb cleaner but I don't have any at the moment. From what I have heard the IAC will cause high idle, not low. I checked all the hoses for leaks but they all look good. Im starting to wonder if its my plenum gasket. Is there possibly something else im missing? I have never dealt with this issue before so any info is helpful. Thanks in advance
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Joined: Jul 2011
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From: Upstate NY
It could be vacuum related still. If you unplug the IAC with the engine cold, it should disengage and go straight to low idle. That tells you it is working. Spray around with starter fluid or an unlit propane torch to see if you find a vacuum leak.
Could be TPS related too. If you have a 3 wire TPS, one will be power, one ground, one signal. I believe the signal is the middle and should be less than 1v at zero throttle, voltage will increase as you open thethrottle.
Could be TPS related too. If you have a 3 wire TPS, one will be power, one ground, one signal. I believe the signal is the middle and should be less than 1v at zero throttle, voltage will increase as you open thethrottle.
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From: Idaho
My TPS tested under 1v. At around .52-.56. With the IAC unplugged she wouldn't start til I plugged it back in. it went straight back to high idle. I will be running the propane torch test tonight when I get home. I was hoping to avoid it but I will also do a more thorough inspection of all my hoses and connections as well. I wouldn't be surprised if I missed something.
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New User
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From: Idaho
So I disconnected the IAC and it dropped to a rough, low idle. I cleaned the IAC and plugged it back in and the high idle returned. Is it possible I didn't get it cleaned out enough? Also, I did the smoke test to check for vaccum leaks. When I removed the large air hoses from the air filter to the manifod there was a pretty heavy smell of gasoline. Just behind the radiator on the passenger side there is some type of plastic "filter box" with two holes in it due to corrosion. That appeared to be the only place the smoke escaped from. I removed the box and plugged the hose that leads into it but it did nothing to fix the idle.
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New User
Joined: May 2018
Posts: 11
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From: Idaho
So I disconnected the IAC and it dropped to a rough, low idle. I cleaned the IAC and plugged it back in and the high idle returned. Is it possible I didn't get it cleaned out enough? Also, I did the smoke test to check for vaccum leaks. When I removed the large air hoses from the air filter to the manifod there was a pretty heavy smell of gasoline. Just behind the radiator on the passenger side there is some type of plastic "filter box" with two holes in it due to corrosion. That appeared to be the only place the smoke escaped from. I removed the box and plugged the hose that leads into it but it did nothing to fix the idle.
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