1993 Oldsmobile 88 Idle too high

Tiny
CHUCK707FLYNN
  • MEMBER
  • 1993 OLDSMOBILE 88
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 250,000 MILES
My engine idles too high after cranking. I've had the idle control valve replaced, then he said he thought the plennum gasket needed replacing. I finally got that thing off and put in a new gasket myself--no sealers were used. But the engine stills revs way too much. Anything else I can check before putting it back in the shop?
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Tuesday, March 17th, 2009 AT 10:20 AM

12 Replies

Tiny
RACEFAN966
  • EXPERT
Ok yes there is we can first check the coolant temp sensor, tps sensor and check for any vacuum leaks. How do the brakes feel? Do they feel normal? Get back to me and we will go from there. You will need a multi meter to check the temp sensor and tps.
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Tuesday, March 17th, 2009 AT 10:55 AM
Tiny
CHUCK707FLYNN
  • MEMBER
The brakes are a little squishy-replaced master cylinder when first bought 100000 ago. Don't know how to use multi meter--should I buy one or just borrow?
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Wednesday, March 18th, 2009 AT 11:51 AM
Tiny
RACEFAN966
  • EXPERT
Ok I would either buy or borrow what ever you would like to do. If you buy one dont get a really expensive one don't spend much more then 25 dollars ok. Here is a pic of what I am refering to ok.


http://www.2carpros.com/forum/automotive_pictures/249564_14572_1.jpg

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Thursday, March 19th, 2009 AT 9:45 AM
Tiny
CHUCK707FLYNN
  • MEMBER
Got the meter! Could use some help with details. I unplug the (tps) and touch which of three prongs? What setting? And what readings on the meter is good/bad? I'm thinking the part behind the master cylinder is sucking air--what needs replacing in this old car then? Can donate more if needed. How do I get these messages posted to my forum in this website instead of just my e-mail/--Chuck.
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Thursday, March 19th, 2009 AT 3:16 PM
Tiny
RACEFAN966
  • EXPERT
OK first do not unplug it ok. You will need a paper clip and you will use that paper clip to back probe down the connector and get contact with the wire terminal ok. Now you will set you meter to the 20 volt scale and hook the red to the paper clip and the black to a good ground or neg side of battery ok.
So back probe the Dark Blue wire and hook up you volt meter and turn the key on engine off the volt meter should read.5 to 1 volt with the throttle closed ok. Now slowly lift the throttle and you should see the voltage slowly and steadly increase with no drops or glitches, when you get to wide open throttle it should read 4.5 to 5 volts. If this tests good then turn the key off and unhook your meter and remove the paper clip.
Now if there is not problem here then check the coolant temp sensor it should be on or near the back left (drivers) side of the engine. It will be a two wire plug in to it. Now unplug this and set you meter to ohms (set at 200k) and touch the wires to the terminals on the sensor itself (not the wire harness) and let me know what it reads and what the temp if at the time of the test. If you do this when it is cold then air temp is fine. Get back to me and we will go from there.
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Friday, March 20th, 2009 AT 9:52 AM
Tiny
CHUCK707FLYNN
  • MEMBER
[quote="racefan966"]OK first do not unplug it ok. You will need a paper clip and you will use that paper clip to back probe down the connector and get contact with the wire terminal ok. Now you will set you meter to the 20 volt scale and hook the red to the paper clip and the black to a good ground or neg side of battery ok.
So back probe the Dark Blue wire and hook up you volt meter and turn the key on engine off the volt meter should read.5 to 1 volt with the throttle closed ok. Now slowly lift the throttle and you should see the voltage slowly and steadly increase with no drops or glitches, when you get to wide open throttle it should read 4.5 to 5 volts. If this tests good then turn the key off and unhook your meter and remove the paper clip.
Now if there is not problem here then check the coolant temp sensor it should be on or near the back left (drivers) side of the engine. It will be a two wire plug in to it. Now unplug this and set you meter to ohms (set at 200k) and touch the wires to the terminals on the sensor itself (not the wire harness)
***Thanx--the tps went up(from just below 1.0) to just below 4 volts at max. The cool. Temp. Sensor showed nothing(cold) @0.5, 50, or 250 mA settings. At the 1K setting it swung to peg at zero (I knew I had contact--; I tried reversing leads also.) It's a $13 part. Soon to replace--right?
Chuck
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Friday, March 20th, 2009 AT 3:10 PM
Tiny
RACEFAN966
  • EXPERT
Ok you are right the coolant temp sensor is way out of range here. Now this may not be a total fix but it needs to be right inorder for anything else to be tested here. So once replaced see how it does and let me know.
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Saturday, March 21st, 2009 AT 8:49 AM
Tiny
CHUCK707FLYNN
  • MEMBER
Sorry it took awhile-finally got both the temp sensor AND the coolant temperature switch replaced! Idle still too high but does seem better.
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Friday, March 27th, 2009 AT 4:23 PM
Tiny
RACEFAN966
  • EXPERT
Ok I would like you to check the vacuum hose to the power brake booster and the one to the PCV valve look for any cracks and check for any intake leaks with a spray bottle of water.
If all that checks out then I would like to test the IAC (idle air control) motor. First you will unplug it and check resistance between term a and b on the motor not the wire harness. Then between term a and c then a and d the resistance should be 40 to 80 ohms if not replace that motor. If it is in spec then you need term b and c then a and d should be infinite if not replace motor. Here is a pic for the term locations and let me know what you find.


http://www.2carpros.com/forum/automotive_pictures/249564_Graphic_58.jpg

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Saturday, March 28th, 2009 AT 9:39 AM
Tiny
CHUCK707FLYNN
  • MEMBER
Thanx again--the ohms on my crap meter only reads in "x1k" which shows around 50 from A to B, the rest don't show. But I just bought another 1993 olds 98 reagency with the exact same motor and I'm getting the same reading. Since I first had the idle valve replaced when all this started- I'm going to assume it was and it is good. All other vacuum lines look OK. Chuck
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Wednesday, April 15th, 2009 AT 10:52 AM
Tiny
JIMMYJACKSON
  • MEMBER
This is what I found on my 93 Olds. After the car starts as I reved it up the idle stayed at a very high idle. After it warmed up I had to turn off the engine and re start it. Then it would idle fine.
Well what I found is that the Throttle position sensor would not return back to the normal idle position. The spring lever that returns the sensor back to the normal position was coated with dirty oil. When it was cold this old dirty oil coated lever would stick and make the engine idle very high. After the engine warmed up this old dirty oil would loosen up and the lever would return back to the normal idle position.
I sprayed the lever with a choke cleaner, this remover the old dirty oil and now the lever moves freely. Now it runs Great in the cold weather.
Bill
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Friday, November 23rd, 2012 AT 4:41 PM
Tiny
RACEFAN966
  • EXPERT
That is great who would have thought it would have been that simple.
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Tuesday, November 27th, 2012 AT 3:14 AM

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