2nd Generation Specific (1986-1992) 1986-1992 Discussion including performance modifications and technical support sections.

Roaming idle on warmup

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Old Apr 9, 2014 | 03:07 PM
  #1  
XSTARSCREAMX's Avatar
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From: Rialto Ca
Roaming idle on warmup

Have this weird issue when my car is reaching operating temp the idle will start to bounce untill it's come to the correct op. Temp. I can't tell what it is. Some told me it was my fast idle. Others told me it was the thermowax pellet which I was thinking.

When it gets to operating temp the idle is sometimes around 1000 and 1100 but so sometimes it's where it should be which is around 750. So I'm not sure if it's a vacuum leak. I've checked a couple times with break cleaner to hear a change in idle but nothing.

Only thing I did before this started happening was clean out my TB with TB cleaner.

Any help would be great.
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Old Apr 9, 2014 | 03:32 PM
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From: YYZ
A fast idle mechanism/thermowax would affect the RPM, but it wouldn't be bouncing around the idle as all they do is keep the throttle plate from closing completely.

The bouncing around comes from the ECU trying to keep the engine running, because the air supply and throttle opening angle and fuel mixture isn't working according to what it should. TPS adjustment may be what's needed. Adjust only when fully warmed up. You can make a tester, search here or online for a 'how-to'.
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Old Apr 9, 2014 | 03:40 PM
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XSTARSCREAMX's Avatar
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From: Rialto Ca
Originally Posted by pfsantos
A fast idle mechanism/thermowax would affect the RPM, but it wouldn't be bouncing around the idle as all they do is keep the throttle plate from closing completely. The bouncing around comes from the ECU trying to keep the engine running, because the air supply and throttle opening angle and fuel mixture isn't working according to what it should. TPS adjustment may be what's needed. Adjust only when fully warmed up. You can make a tester, search here or online for a 'how-to'.
Cool thanks for the info man
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Old Apr 9, 2014 | 05:51 PM
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roTAR needz fundZ
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From: Freeland, MI
mine does the exact same thing, except I've adjusted my TPS many times and am positive its set correctly.

Every time mine does it though, I can hear my BAC valve click everytime the RPMs drop, so I'm not sure if my BAC took a crap when it WAS working perfectly, I've just been living with it, even though it does annoy me, along with bucking in the low speed range lol
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Old Apr 9, 2014 | 06:11 PM
  #5  
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From: Rialto Ca
Originally Posted by lduley
mine does the exact same thing, except I've adjusted my TPS many times and am positive its set correctly. Every time mine does it though, I can hear my BAC valve click everytime the RPMs drop, so I'm not sure if my BAC took a crap when it WAS working perfectly, I've just been living with it, even though it does annoy me, along with bucking in the low speed range lol
Yeah it annoys the **** out of me haha
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Old Apr 10, 2014 | 01:28 PM
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From: YYZ
A lot of people have trouble setting the TPS properly.

One of the reasons is you have to make sure the engine is warm enough and the fast idle cam at the back of the TB has released the plates to close completely. With age (thermowax) or messing around with the rear adjustments, sometimes the cam never releases when the engine is warm. This causes people to set their TPS as 'throttle closed' when it isn't really.
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