High Idle

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poppincaps88

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Oct 23, 2005
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Hey everybody, I'm having trouble with the idle in my 87 supra turbo.

It starts up and revs to 1500 as it warms up. After it reaches operating temperature it drops to about 800 or 900. I'll come to a stop at a redlight and the idle will then be sitting at about 1000 or 1200. It sometimes goes down a little if I turn the car off and turn it back on but it never drops down to where it's supposed to be. I thought vacuum leak but I havn't been able to find one. TPS or ISC maybe? Could a bad throttle cable cause the problem? Maybe the throttle just needs to be adjusted?

Any help would be great. THanks A lot you guys.
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
poppincaps88 said:
Hey everybody, I'm having trouble with the idle in my 87 supra turbo.

It starts up and revs to 1500 as it warms up. After it reaches operating temperature it drops to about 800 or 900. I'll come to a stop at a redlight and the idle will then be sitting at about 1000 or 1200. It sometimes goes down a little if I turn the car off and turn it back on but it never drops down to where it's supposed to be. I thought vacuum leak but I havn't been able to find one. TPS or ISC maybe? Could a bad throttle cable cause the problem? Maybe the throttle just needs to be adjusted?.

Any help would be great. THanks A lot you guys.
Click to expand...


Hmmm...what is it with all these idle problems lately? First, do you hear the ISC step back just after you shut the engine down?

Second, just because you have't found a vacuum leak doesn't mean there isn't one. Next time the idle is high with the engine warm pinch closed the ISC hose from the accordian. Either that or remove it and plug. Does the engine die? Third, be sure the throttle plates are fully closed. Fourth, jumper E1 and T in the diag block and open the throttle a bit with the engine off. Do you get a code 51?

If you can confirm all these things then leave the block jumpered, warm the engine up to operating temp, remove the rubber cap on the throttle body and see if you can adjust idle speed to 650 or so. There could be other causes but as the man said, you have to start somewhere. You can disconnect the throttle linkage to check for stickiness in either the linkage or the cable. Based on the symptoms my initial bet is a vacuum leak. Does it idle up when the headlights are on? When the A/C is on?
 
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poppincaps88

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Oct 23, 2005
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jetjock said:
Does it idle up when the headlights are on? When the A/C is on?
Click to expand...

The ISC doesn't make any kind of sound when the engine shutdowns.

It does idle up slightly when either of those are turned on.


I'll defintely go over all the things you mentioned once it stops raining. THanks a lot you guys for the responses and I'll keep you posted. :icon_surp
 
jetjock

jetjock

creepy-ass cracka
Jul 11, 2005
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Redacted per Title 18 USC Section 798
poppincaps88 said:
The ISC doesn't make any kind of sound when the engine shutdowns. It does idle up slightly when either of those are turned on.
Click to expand...


The odds are very slim it'll do one without the other so you need to make absolutely sure it's not stepping back a few seconds after engine shutdown. Have someone stand there and listen or open your hood and window and listen carefully.
 
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poppincaps88

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Oct 23, 2005
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Ok so I checked to make sure my ISC wasn't stepping back and it isn't. I thought my idle rode up a little when I had my AC on but I guess it doesn't after looking at it again. So I'm thinking it has to be a vacuum leak...now the problem is finding it...:icon_conf
 
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