Too high and fluctuating idle on 93 SE - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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Old 07-10-2006, 11:11 PM   #1
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Default Too high and fluctuating idle on 93 SE

Fellow Bonne Owners,

I have a 93 SE with only 98k miles on it. I have recently been having problems with idling. My problems are the car will intermittently idle too high when in drive and at a stand still. For example, she'll start out where she should be at about 800-900 rpm and then after I drive on the freeway for a while and come to a stop again, she will increase to 1300-1500 and sometimes higher. If I shut her down and restart at a light or in a parking lot she will often, but not always, kick back down to at least 1000 rpm. And then if I once again increase my speed by freeway driving (65-70 mph) she will do it again. I have checked the other posts and started with the most obvious this past Saturday-a thorough cleaning of the throttel body, IAC and MAF sensor. I also disconnected the battery so the computer could reset. She started out ok the first few times after the cleaning and then started doing it again-in fact, this morning, when first started she immediately jumped and stayed around 1500-1750 rpm until I shut down and restarted 3 times. Then she idled at normal speed for awhile until I had to make a trip to a customer site that required about 45 minutes of freeway driving and did the same thing again when I exited-idled at about 1250-1500 rpm. Any one have any other ideas on how to stabilize the idle speed when at a stand still at around 800 rpm?

Thanks!
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Old 07-11-2006, 08:44 AM   #2
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Is the check engine light on?

Any way you can get it scanned to check out where the car is reading IAC and TPS sensors?
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Old 07-11-2006, 09:27 AM   #3
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Default Too high and fluctuating idle on 93 SE

No, my check engine light is not on. I do not have a way to check codes right now unless I take it some where and pay $85 for hook up, which I would like to avoid. Any other ideas?

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Old 07-11-2006, 09:53 AM   #4
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Neat thing about your 93, it is the last year you can retrieve codes yourself.

Techinfo: How to retrieve codes 87-93

Please check this way and expect code 58 as it'* a known bug.
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Old 07-12-2006, 09:22 AM   #5
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I checked the codes and unfortunately did not get any error codes at all. I then disconnected the battery for about 10 minutes and took for a test drive. Started and idled fine, even after about 10-15 minutes on freeway. Started up again this morning and idled at about 1250. Went to my destination. When started back up, idled fine. This is freaky. Any other suggestions?

Thanks again for you help!
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Old 07-12-2006, 09:27 AM   #6
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Not really...others will jump in soon.

It seems as though one of the sensors is commanding the high idle. Idle Air Control aka IAC is a prime suspect. Possibly pull and ensure it'* clean.
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Old 07-14-2006, 10:33 AM   #7
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I had just cleaned the IAC so I went ahead and replaced it las night. Seems a little better but still idled around 1250 after a test drive on the highway. At normal driving speeds of 35-45 it returned to idle at 800-900.

What is code 58 an indication of anyway? Is it something else I should go ahead and replace even though I did not get the code?

Thanks,
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Old 07-14-2006, 10:40 AM   #8
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58 is a known bug that means nothing.

Think of it as a friend that lets you know...that you are pulling codes correctly.
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Old 08-16-2006, 10:37 PM   #9
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Did you ever get the high idle issue resolved? My 93 Bonnvizzle SE is doing the same. I have just started researching the forum for possible solutions.

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Old 08-16-2006, 11:36 PM   #10
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Go back to the basics, which in this case doesn't cost much.

With no codes, and IAC cleaned, check for vacuum leaks. (Especially if you have a fluttering idle.) Not a gaurentee, but if I had a nickle for every time this was the culprit....well you know.

Pinch off hoses, or use a propane torch (without the flame). Turn the gas down low, and put the tip near every vacuum line connector. If you have any RPM change, you have a good candidate. If you have any 'soft and mushy' vacuum lines, just replace them.


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