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Hi: I have a 1993 GMC Safari Van that has a problem with ...


Sent to Car Experts June 13, 2007 7:48 p.m.
Hi: I have a 1993 GMC Safari Van that has a problem with fast idle. At first it was an intermitten problem, for no apparent reason, the idle would increase to very fast RPM's & the check engine light would come on. I would turn the enging off, let it sit for a few minutes, then start it back up. The idle would be normal & the check engine light would be out. I then drove it normally wothout no apparent problems. It seemed to do this when the engine was first started & cold, but after it warmed up a bit, the problem would go away. When it did this again, the very fast idle & check engine light came on, I took it to a shop & the mechanic checked for codes. He got a TPS code (throttle position sensor) & said I should change it. Well I did that & at first everything look to be normal again. So, I drove it around abit & everything looked to be OK. But after I stopped for a light & started to accelerate, the high RPMs returned & the check engine light came on again. Help Me. Thanks

Optional Information:
1993 GMC Safari 4.3L

Already Tried:
Changed TPS as per code provided & recommendation of mechanic that tested for codes. Replacing TPS seems to have made the problem worse.
Customer (name blocked for privacy)
Status: Closed   Value: $15   
Info Request
June 13, 2007 7:58 p.m. (10 minutes and 34 seconds later) 		REPLIED to Info Request Check Mark
Have you had the van tested for codes since the replacement of the TPS?

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Reply to carhelp4uhere
Sent June 13, 2007 8:02 p.m. (3 minutes and 30 seconds later)
Yes. It still shows a TPS code. The problem has gotten worse since I replaced the TPS. The problem went from an intermitten one to a full blown proble. The vehicle runs at high RPM's & whe it's put into gear & then inot park again, the RPM's really increase & the only recorse is to turn off the vehicle.
Customer (name blocked for privacy)
Info Request
June 13, 2007 8:15 p.m. (13 minutes and 48 seconds later) 		REPLIED to Info Request Check Mark
Are you getting code 21 or 22?

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Reply to carhelp4uhere
Sent June 13, 2007 8:16 p.m. (47 seconds later)
Code 22
Customer (name blocked for privacy)
Info Request
June 13, 2007 8:37 p.m. (20 minutes and 49 seconds later)

This is where you will need to start checking the wiring and to see how everything is operating. You need a volt meter to check these items. Do you have tha ability to test wires with a voltmeter. One with fine points is what you need. You will need to test three wires.



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Reply
Sent June 13, 2007 8:40 p.m. (2 minutes and 33 seconds later)
I think I can get a hold of a volt meter. Which three wires & what should I be looking for & what are your recommendations?
Customer (name blocked for privacy)
Answer
June 13, 2007 8:54 p.m. (13 minutes and 52 seconds later) 		ACCEPTED Check Mark
At the tps connector with the key on you need to check the tps ground and reference wires. The reference (power wire) wire is gray and the gound is black. With the voltmeter in between them you should have 4.9-5.1. The third wire is the signal wire to the ecm. With the tps hooked up, back probe the sensor and see what the signal is. You will have to ground your meter and measure for volts to find the signal. With the engine not running, the voltage should be close to 1 volt. After you do this you should check it at wide open throttle it should be atleast 4.3. Let me know how you make out. If everything checks out here we need to test the signal wire at the ecm. It will be a dark blue wire and could be in position C13 (manual trans) or A15 (automatic). Let me know if you have any questions.

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Reply
Sent June 13, 2007 9:01 p.m. (7 minutes and 49 seconds later)
I do have a question. What is the connection between putting the van in gear & the idle really increasing & the idle remains increased when it is put into park? When the engine is shut off & then restarted after about a minute or two, the idle drops down, but not as fast, until it is put into gear again?
Also, is it possible that the ECM could be bad?
Customer (name blocked for privacy)
Answer
June 13, 2007 9:08 p.m. (6 minutes and 55 seconds later)
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Reply
Sent June 13, 2007 9:14 p.m. (5 minutes and 37 seconds later)
You mentioned 2 codes, code 21 & code 22. What is a code 21?
Customer (name blocked for privacy)
Reply
Sent June 13, 2007 9:34 p.m. (20 minutes and 18 seconds later)
What is a code 21?
Customer (name blocked for privacy)
Answer
June 13, 2007 9:42 p.m. (7 minutes and 34 seconds later)
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