Faulty TPS or MAP sensor?
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From: College of Charleston, SC
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Faulty TPS or MAP sensor?
Half the time, my idle is too high, and half the time it won't idle. My idle jumps all over the place when sitting, park and drive. In park, the revs usually are around 1500, and in drive around 1000. I have not messed with the idle set screw on the TB.
After I drive about ten minutes, the revs may suddenly fall at a stop light, and I have to keep my foot on the gas to keep the engine going. When I went out to start my car today, it would not stay alive from the beginning.
I have already replaced the IAC, and cleaned the TB. There don't seem to be any vacum leaks. I pulled the codes, and a 33 showed, which is a high reading from the MAP sensor. This code just now showed, even though this idle problem has been an ongoing problem for a month now. Could it be a bad TPS or MAP sensor.
After I drive about ten minutes, the revs may suddenly fall at a stop light, and I have to keep my foot on the gas to keep the engine going. When I went out to start my car today, it would not stay alive from the beginning.
I have already replaced the IAC, and cleaned the TB. There don't seem to be any vacum leaks. I pulled the codes, and a 33 showed, which is a high reading from the MAP sensor. This code just now showed, even though this idle problem has been an ongoing problem for a month now. Could it be a bad TPS or MAP sensor.
Pro
Joined: Dec 2001
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From: NYC NY
Re: Faulty TPS or MAP sensor? (vettes rule)
I wouldn't mess with the idle screw unless you are willing to do a idle air set. If you do, you will likely just throw off yuor tps voltages relative to your air flow. Check tech tips on how to set you tps and idle screw.
Your MAF may also be the culprit. The best way to check this is to find someone who has one and borrow it for a few minutes for your car. If it runs better you probably have a MAF problem. You can also try disconnecting yours and running it without it, if it runs better you may have found the problem, but I would double check it with a working unit.
My car has had problems idling for the last year, and after checking everything I could think of twice I finally figured out the MAF was bad. Check everything else first though as a rebuilt MAF will run $150 or so.
Good Luck
JEff
EDIT: sorry I just now noticed you have a 91 not sure if the MAF is the quite the same as mine. Should be similar if you are still a TPI.
[Modified by C4-Wolf, 3:40 PM 6/16/2002]
[Modified by C4-Wolf, 3:40 PM 6/16/2002]
Your MAF may also be the culprit. The best way to check this is to find someone who has one and borrow it for a few minutes for your car. If it runs better you probably have a MAF problem. You can also try disconnecting yours and running it without it, if it runs better you may have found the problem, but I would double check it with a working unit.
My car has had problems idling for the last year, and after checking everything I could think of twice I finally figured out the MAF was bad. Check everything else first though as a rebuilt MAF will run $150 or so.
Good Luck
JEff
EDIT: sorry I just now noticed you have a 91 not sure if the MAF is the quite the same as mine. Should be similar if you are still a TPI.
[Modified by C4-Wolf, 3:40 PM 6/16/2002]
[Modified by C4-Wolf, 3:40 PM 6/16/2002]
Heel & Toe
Joined: May 2002
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From: Mantua NJ
Re: Faulty TPS or MAP sensor? (vettes rule)
I would go back and check your IAC. I left mine unplugged after changing the water pump and it was doing the same thing. Unplug it and see if anything changes.
Safety Car
Joined: Feb 2002
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From: Sun City West Az
Re: Faulty TPS or MAP sensor? (vettes rule)
Try tapping on the bottom of the MAP while it is idling. See if that changes the idle speed. If it does, replace the MAP. Also, disconnect it, if there is no change in the performance, replace the MAP.
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Re: Faulty TPS or MAP sensor? (ittlfly)
Where is the MAP sensor? The Haynes manual says it's near the left rear of the intake manifold, but I don't know what it looks like.
Safety Car
Joined: Feb 2002
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From: Sun City West Az
Re: Faulty TPS or MAP sensor? (vettes rule)
On a 92, as I RECALL...it's on the pass side of the intake, on top, at the TB connection. It;s oblong, (about 3" long) and I think the electrical plug is on the bottom. I'm not at home at present (no books or car with me) and I'm shooting from the hip here. Maybe somebody will jump in with exact info for your year.
Heel & Toe
Joined: May 2002
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From: Mantua NJ
Re: Faulty TPS or MAP sensor? (vettes rule)
I don't think the 91 and 92 are the same. If you look on page 1 -5 of the Haynes manual you can see the MAP just behind the throttle body on the 92 and up. It is the black unit right on top of the plenum. It has a connector that comes up from underneath and a vacuum port that goes directly into the plenum that you can't see without removing. Look for a similar sensor or module where the manual says with a direct vacuum connection to the manifold.
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Re: Faulty TPS or MAP sensor? (MEBVette)
I found the sensor by using a MAD catalog :crazy: . It's on the passenger side at the back of the plenum I think. The replacement sensor in the MAD catalog and the sensor above look the same.
Would a faulty MAP sensor do this?
Would a faulty MAP sensor do this?
