Idle issues, need input please.. - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 04-13-2005, 07:12 AM   #1
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Default Idle issues, need input please..

87 bonnie

Idles [email protected] 2k RPM for 10 minutes then gradually drops to 900. I remember one of my buddies screwing with the TPS a while back because the car would [email protected], then gradually lower until it would stall when stopping. What he did fixed the stalling problem, but the high idle when cold is making it hard to drive. i have replaced the IAC also, but i did not notice a change, even afer cleaning the TB. My questions are...

Roughly what should the idle be at Warm, also when its first started cold?

He adjusted the idle screw in a bit, is this normal? everywhere i read, the throttle plates have to be closed completely when no throttle is given. but if i adjust it that way, it does not stay running.

is there a way to adjust the TPS w/o a scanner, by using a multimeter to test voltage?

was the TPS the cause of my stalling problem, or did he just make it run anyway he could?

it is also throwing a 32 EGR code, but its been that way for a long time now.

thanks
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Old 04-13-2005, 10:33 AM   #2
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My car idles at about 1500-1600 rpms when it is cold, and gets down to about 600-700rpm'* when it is warm. That is after I changed my ICM and Coil Packs. With the magnavox ignition I idled at about 900-1000 warm. If the IAC is bad enough it can cause you to stall when coming to a stop. Did you notice your RPMs "hunting" around before the IAC was replaced? I am not too sure about the TPS but someone else here will fill it in.
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Old 04-13-2005, 10:38 AM   #3
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>Roughly what should the idle be at Warm, also when its first started cold?

Around 700 rpm

>He adjusted the idle screw in a bit, is this normal? everywhere i read, the throttle plates have to be closed completely when no throttle is given. but if i adjust it that way, it does not stay running.

Should never touch the idle screw. Throttle plate should be closed at idle. All air goes through IAC passage. Screw is to keep plate from closing too far and sticking.

>is there a way to adjust the TPS w/o a scanner, by using a multimeter to test voltage?

Yes, center lead should read .37-.42v at idle and over 4v at wide open throttle with key on. (Engine does not need to be running). To adjust you remove the vent tube, loosen the two screws, and rotate the TPS. Just bending the tab is rong.

<rant>Every owner of a 80s or 90s car should have two things: a factory service manual and a scanner. Can get both for under $100 if you look.</rant>

>was the TPS the cause of my stalling problem, or did he just make it run anyway he could?

Probably not but can sure screw up an idle. Will generally set a 21 or 22 code if really bad.

>it is also throwing a 32 EGR code, but its been that way for a long time now.

if you have a stuck open EGR the idle will be bad.
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Old 04-13-2005, 11:04 AM   #4
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I've still got the stock magnavox ignition on mine from '87. Well not quite, the stock coil pack was replaced at 57xxx miles but it'* got 205k on it now. As far as i can see the module it still original. My car idles ~ 1600-1800 cold and it'll settle down to a nice 650-700 hot. I've also got the EGR code 32 but that only effects warm restart idle. For me at least.
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Old 04-13-2005, 04:07 PM   #5
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Back when I had some cooling system issues, I had the same problem. The car would start up just fine, idle at 1k [what it shows on the tach.. normal for me], then I tap the throttle [always do that on cold start.. just get everything flowing.. never above 2500RPM], then the idle wouldn't go down for a minute. It chose to stay at 1600RPM. After a few minutes, and a few more throttle taps the RPM would drop down to 1k. I know what you mean by it is really hard to drive the car like that. The problem was just about fixed, right when I lost power brakes, so keeping the car from moving at 1600RPM was VERY difficult. And was like Neutral bombing it when trying to put her in gear. Once my cooling issues were resolved, this was no longer a problem. Yeah, on a cold morning after not being run for a week she still does this [automatically, not from tapping the throttle], and all it takes is a little tap on the throttle, and about 30 sec wait time, then she drops right back down.

Try tapping the throttle lightly [don't go over 2.5K RPM with a cold engine], and waiting a little bit. I think the EGR Code may be why the car idles poorly.. but don't quote me on that. To check if an LG3 EGR Valve is stuck open ['87 engine], find it, and push on it towards the block. If it moves, then it isn't stuck open. If it does move, then it is fine. If it is stuck, try pulling it out, but be careful how much force you put on it. If it has a little resistance, try moving it a little to see if that helps. I'm not sure about lubricating it, since it does interact with hot exhaust fumes.. cleaning it may be the best solution. Not sure how to do that.


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Old 04-13-2005, 06:55 PM   #6
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Idle function is a variable based on coolant temperature however it should drop under 1000 rpm when the coolant goes above 40C. Of course if the coolant sensor is toast...

Bad TPS can also result in a high idle. Time for a scan tool.
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Old 04-13-2005, 08:21 PM   #7
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thanks for the help guys. after briefly looking at it today i noticed the idle screw is in roughly 2 turns from closed throttle plates. from all this info, it seems like my buddy adjusted the TPS so the idle was considerably lower than normal, then compensated with the idle screw.

--Did you notice your RPMs "hunting" around before the IAC was replaced? I am not too sure about the TPS but someone else here will fill it in.

The idle at warm flucuates between 7 and 900 rpms. its not up and down either, its solid 900 sometimes, other times solid 700.

i will check the TPS voltage at idle and adjust it accordingly, then i will fiddle from there.

Another question i have is how to get the stupid EGR valve off. the mounting screw is in a place i cant even custom bend a wrench to get in. i should probably check resistance on the coil packs too. ill keep posted what ive done, and if it fixes anything..

thanks again for all your help!
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Old 04-13-2005, 08:42 PM   #8
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If you have not done this, remove your IAC, and clean it thoroughly. 16 years of grime came off to a sparkling shine on my car. Just have at it. I also only used WD-40 to clean it.. so it isn't difficult. Also, you should be able to move it by hand.. not easily.. but it shouldn't stick or anything like that.


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Old 04-13-2005, 09:52 PM   #9
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Quote:
Originally Posted by padgett
Idle function is a variable based on coolant temperature however it should drop under 1000 rpm when the coolant goes above 40C. Of course if the coolant sensor is toast...

Bad TPS can also result in a high idle. Time for a scan tool.
I agree its time for a scantool... Once things have been adjusted or messed with, they need to be brought back to factory spec'* before the prblem can be corrected.... At the same time a scantoll will be a huge help in all of these areas..

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