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1992 Pontiac Grand Am Stalling and Revving

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KATJAFALLINGSTAR
  • MEMBER
  • 2 POSTS
I am writing from Canada yet we are having quite a mild winter this year. It is only -10 degrees farenheigt tonight. Im not sure if this is part of my problem or not. My car is doing a number of strange things.
1. When I step on the gas pedal after idling the car seems to "stick" ; it takes about five seconds to react and the RPMs go way up anywhere from 3000 to 4000 and really revs up, then when it does react to my foot on the pedal and speeds up the RPMs go back down to about 1000. Also when it finally does speed up it seems to do so very suddenly, it kind of jerks ahead.
2. When stepping on the brakes; ie- at a red light, the car seems to struggle to keep from stalling; lights dim, shakes mildly, grunts a little etc..., and sometimes it does in fact stall if I step on the brake too suddenly/not gradually enough.

I only seem to have these problems when driving between 1-40 or 50 Km per hour.

Any ideas?
Feb 2, 2006 at 1:50 PM
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SC1 RACING
  • ✓Experienced Mechanic
  • 117 POSTS
that sounds like a combanation of the tps, and the iac sensors.
Feb 3, 2006 at 5:47 AM
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MVANNESSJR
  • ✓Experienced Mechanic
  • 223 POSTS
I'd agree with SC1. The rev problem sounds like the TPS (about $30-$40US for a new one, not hard to do yourself but this is under $100 to fix usually). The stalling sounds like the IAC. The IAC may be full of carbon deposits. I'd recommend cleaning it before going out and replacing it.
Feb 4, 2006 at 12:21 PM
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KATJAFALLINGSTAR
  • MEMBER
  • 2 POSTS
I brought my car to the service station and described my problems. It cost 25 dollars for labour (they charge 50 dollars/hr) and 13 dollars for a new air filter, so about 43 dollars with tax. The receipt says "running clear mass air flow". However, my car is still "trying" to stall when I decelerate and there is still a sluggish throttle response. And I thought that if the mass air flow sensors are dirty that it can cause a faulty MAF reading...? So is the MAF reading really that reliable?

It doesn't look to me as though they even checked the IAC or the TPS . So I called them back when I got home and they said it might be the fuel pump. Should I be more persistent about servicing the throttle body?
Feb 9, 2006 at 10:23 AM

Suggested Repair

Clean the idle air control (IAC) valve of carbon deposits before replacing it, and inspect or replace the throttle position sensor (TPS). The experts linked the high revving and delayed throttle response to the TPS and the stalling under braking to a dirty or faulty IAC.

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Conversation Summary

A 1992 Pontiac Grand Am owner reported delayed throttle response with RPMs surging to 3000-4000 before dropping, sudden acceleration, and stalling or near-stalling when braking at low speeds. Two experts agreed the symptoms point to the TPS and IAC, recommending the TPS be checked or replaced and the IAC cleaned of carbon before replacement. The owner later had a shop replace the air filter and report a clear mass airflow reading for about $43, but the stalling and sluggish throttle remained. The shop then suggested a fuel pump, and the owner asked whether the throttle body, IAC, and TPS should still be serviced.

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