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Old 02-15-2002, 06:54 AM
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Red face High idle in my daily driver!!!

Roy told me I should ask on here about my current car because we have so many good mechanics here. The car in question is a 1995 Buick Skylark Custom with a 3100 SFI engine and 113,000 miles. Here's the problem. When the car is started in the morning, the engine races. It's not just a cold weather fast idle; it's like someone is actually pushing on the gas. When put into reverse, the idle drops down and I'll then pull out of the garage. While driving, the engine sounds very nice and still has the power that it always has had. I'll get to campus (about 5 miles) and I can then put it back into Park or Neutral and the idle will be fine. After the car sits for about another 8 hours, I'll go to drive home and the same thing happens.
After talking with Roy, here are the things I've done: replaced idle air control, cleaned idle air passages in throttle body and the throttle body itself, cleaned IAC, TPS, and intake air temp. sensor connectors. I'm probably going to replace the air filter and PCV this weekend and check my grounds for the comp.
Does anyone have any words of wisdom for me on this situation? I did notice that the intake plenum was kind of skunky, so should I clean that? How should I approach that cleaning?
Thanks for the help guys! Any advice or comments are helpful and appreciated!

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Old 02-15-2002, 11:02 AM
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Try replacing the coolent temp senser, With a black plug that has 2 wires a yellow and black.Does your rad cooling fan run on cold start up? Some GMs will if this senser is bad allso have high idle.
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Old 02-15-2002, 11:26 AM
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If the coolant temp sensor was bad, would that also screw up my temp gauge? The only reason I ask is because the gauge is fine, but I know that the temp sensor also sends info to the IAC.
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Old 02-15-2002, 03:56 PM
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ECT and temp gauge senders are two separate senders. Do you have a scan tool to check for codes that might be stored? If ECT is out of its paramiters it wouldn't set a code I don't believe,but it would send a faulty signal to the ECM.
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Old 02-15-2002, 07:37 PM
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Thanks guys I worked for GM for years and wish I knew and could remember everything. I started this club just for this reason because no matter good you are you can always use help. You mechanics know how hard it is to fix a computer car by email.Lets see if we can fix this one. Check all the grounds. ROY

[ February 15, 2002: Message edited by: Roy Newton- exprotech ]</p>
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Old 02-17-2002, 07:56 PM
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So let me get this straight. If my coolant temp. sensor is bad, the gauge could be reading fine, but it could still be causing a problem of some sort? This is the one that's located by my thermostat correct?
I'm thinking that if my trip back home next weekend doesn't help any, I'll just replace the coolant temp. sensor (based on the answer to above question!)
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Old 02-18-2002, 03:44 AM
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Coolant temp sensor has nothing to do with the temp gauge. When you install it DONT put any sealant or tape on it. I would not attempt to repair the newer stuff anymore without a scan tool or diagnostic,s machine. Your just guessing and will spend more in parts than the shop will charge you. But cleaning the t-body and checking the iac valve are good things to keep up on every 40-50K. That car did have problem with grounds and the wiring to the iac valve i beleive. Have a good shop also run a good fuel injection cleaner through it(pressurized with the fuel pump shut off) When your all done change the o-2 sensor also(its like spark plugs it dont last forever) Good luck. I had one about a month ago that drove me nuts(emmission problem).In thinking about it,the ground is probaably bad if it stops after you go in rev.Just put a new ground from the engine to the batt or body see if that helps.

[ February 18, 2002: Message edited by: Phat ]</p>
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Old 02-18-2002, 04:58 AM
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Are the grounds you are talking about in the engine compartment or are they actually located in the car some where? I see two behind the battery that look kind of dirty, so I thought that after this weekend, I would take them off and clean them off and see if that helps. Are there others inside the car that I need to take care of?
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Old 02-19-2002, 12:15 PM
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I was thinking maybe it was the oxygen sensor it sounds like you have pretty much fussed with everything else. If it isnt a grounding problem i would change the sensor. I chased a problem similar to this around one time, but on a dodge spirit. The sensor must have been sending the computer some squirrely signals and it would run decent on start up, but after a small amount of time, the idle would come down, yet run like a real turd. Supposedly the computer will look at the signal and try to respond to it for a fixed length of time. after that time has expired, it basically ignores that sensor and goes into a preset closed loop condition where it will not look at the sensors. I dont know if this helps , but i hope you have some luck soon!
GOOD LUCK!
P.S. by unhooking the battery and reseting the computer trouble codes does it go away for a while?
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Old 02-19-2002, 12:19 PM
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You know, that's a good question. Maybe I'll do that when I clean the grounds. I'm still not convinced that the IAC isn't set. I haven't really driven that much and the driving I did is all short city trips.
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