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Fast idle


oldhdman

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A couple weeks after getting my 1997 Eldorado while driving I noticed a very fast idle.Istopped

shut off the engine,checked for anything unusual under the hood,started back up,and it was fine.

Sunday it did it again,but this time it would'nt go back to normal.Took it to the local dealer they

said it had a bad fuel rail,however there is a current recall,and the repair would be no charge.

I thought that was cool. I picked it up tonight,and on my way home it did it again.After restart it was normal again.

Any ideas?

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Clean the TB. Do a search and you will get lots of info on it. Most likely there is a carbon build up in there and the throttle plate is not closing completely. It's not a hard job.

BTW, WELCOME!

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Thank you.I did'nt mention it in my first post,but the dealer recomended a tb cleaning while they were working on it anyway so I figured ,why not they were right there.Only $45.

By the way,I've made quite a few posts,but I'm showing only a couple.I assume its because of the forum's recent problems

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Sounds like your Idle Speed Controller (ISC) may be giving you problems. There are many previous threads about this, including diagnosing, cleaning and replacement. I have some info on this if you can't find it doing a search.

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Since the dealer did the TB cleaning, you might take it back and tell them it not right and let them correct it. On the other hand, they will likely find $omething el$e wrong with it. You might check the idle control valve as mentioned.

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Remember, the board's database went back to the 30 November version, so any activity since then is not registered.

Jason(2001 STS, White Diamond)

"When you turn your car on...does it return the favor?"

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Went back to dealer this morning,they told me to bring it back in.The sercice manager said my throttle body was very dirty it may have grooves worn in it.I mentioned the ISC and the IAC he said he thought they would set a code,but no codes were found.He thinks I may need a new TB.I did'nt ask him,but does anybody know how expensive a TB is?It is still an intermittent problem since they worked on it,shut off engine, after restart it will idle normally for a while then back to very fast again.Very frustrating.

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If your TB has "grooves" in it, they put them there scraping the carbon out. Carbon should never be scraped out with a scraper, screwdriver or the like. It should be cleaned with carb cleaner, a toothbrush and rag as the TB is aluminum, thus rather soft.

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Dealer could'nt look at it until Thursday so I went home unhooked the battery while I cleaned the car.Then went for a drive,about thirty miles, and the car was flawless.I don't know if disconnecting the battery had anything to do with it or not.I'll keep you posted.

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If your TB has "grooves" in it, they put them there scraping the carbon out. Carbon should never be scraped out with a scraper, screwdriver or the like. It should be cleaned with carb cleaner, a toothbrush and rag as the TB is aluminum, thus rather soft.

I agree with Ranger. If there are grooves present, they were probably made while doing the cleaning. I checked the price for my throttle body as there appeared to be grooves in mine as well, and I can't remember exactly what it was, but it was very expensive. I checked Rockauto.com and there wasn't one listed there.

I had high idle problems when I first bought my caddy, and after cleaning my throttle body, same idle problem. Turned out being the ISC motor. There were no codes set, so I wouldn't rule that out as being the culprit. Does your ISC make any ratcheting noises when you turn it off? I have some self diagnosis post I saved about this if you plan to check it out yourself. Let me know if you need them and I'll post them.

Dealer could'nt look at it until Thursday so I went home unhooked the battery while I cleaned the car.Then went for a drive,about thirty miles, and the car was flawless.I don't know if disconnecting the battery had anything to do with it or not.I'll keep you posted.

You are supposed to disconnect the battery after doing a TB cleaning so the idle can relearn. I wonder if the dealer had done that. Could you tell if the battery was disconnected after you picked it up from the dealer...i.e. fav. radio channels not there, clock wrong?

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I've always lost my radio stations, can't remember the clock, but then I've never disco'd mine for only ten minutes. I'm guessing there must be a battery in there then, and maybe after so much time has passed, you lose those settings???

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If the problem persists, the problem might be a defective or sticking Idle Air Control valve. That vintage of Northstar does not use an idle speed control motor like the earlier Northstars and 4.9s.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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