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Frank, Auto Service Technician
Category: Car
Satisfied Customers: 3420
Experience:  33 years experience,25 with GM,14 ASE certifications,
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1995 Buick Lesabre: 3.8 Check engine light come on..vacuum line

Resolved Question:

1995 Buick Lesabre, 3.8 Check engine light come on. I noticed a bad vacuum line replaced it. The check engine light went out.   But the car is idling too fast not. I tried replacing the idle control switch, it did not make any difference. any suggestion on how to slow down the idle.
Submitted: 10 years ago.
Category: Car
Expert:  Frank replied 10 years ago.
Its best if you have a scanner.A tps that is reading too high will cause a fast idle.Also a cold running engine.A quick check of the parameters + what the iac counts are.If they are zero,then you have a mechanical fault such as a bad iac valve or vacuum leak or throttle plates not closing(the last would show high tps voltage as well-over .6 volts.If the iac counts are say 80,then its a command from the computer and the computer thinks it need the rpm like if the a/c was on or its in gear.
Customer: replied 10 years ago.
Reply to Frank's Post: The throtle plate is closing. what is a iac value, and there is no vaccum leaks
Expert:  Frank replied 10 years ago.
IAV value on a scanner should show 10-40 counts at slow idle normally.Try this.Remove the iac valve and disconnect and see if you can get your finger into the bottom of the bore to plug the passage.Have some one start it.It should idle slow or won't idle at all because its too low.Your trying to be the iac valve-which controls idle speed by regulating a controled vacuum leak.If you can block the vacuum and control the idle it's going to be a IAC or control problem and you need a scanner to see what the command is.Match the iac valve to be sure they sold you the right one.The shape of the pintle is important.
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