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Engine surge

Tiny
JIMSMITH2354
  • MEMBER
  • 2003 PONTIAC GRAND AM
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 80,000 MILES
While driving slowly as in a parking lot, if I let the RPM's go down to 500, the engine will surge up to 800. While it is only a short time, it is a little scary. It has been happening since new, and many trips to the dealership - found no problems. Engine warm of hot, with AC ON or wires pulled. I have cleaned the intake manifold system, replaced the throttle pot, idle air control, MAP sensor, disconnected the EGR valve, plugged various vacuum hoses, injected propane into the dipstick, all with no fixes.
I have replaced the engine computer with a performance programmed unit and while the performance is much much better, the idle surge is still there.
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Monday, February 7th, 2011 AT 8:00 PM

9 Replies

Tiny
RASMATAZ
  • MECHANIC
  • 75,992 POSTS
Check the fuel pressure if its within specs if okay clean and test the MAF sensor
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Monday, February 7th, 2011 AT 8:13 PM
Tiny
JIMSMITH2354
  • MEMBER
  • 8 POSTS
Yes, the dealership did the fuel pressure check and said the MAF sensor was OK. The engine runs to redline without a miss. (The new engine computer has no rev limiter)
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Monday, February 7th, 2011 AT 9:13 PM
Tiny
CHEV_MAN00
  • MEMBER
  • 18 POSTS
  • 2002 PONTIAC GRAND AM
  • 3.4L
  • 4 CYL
  • 217,000 MILES
Ok so I have had this problem for sometime now, since I bought the car. I have googled the problem and replaced the sensors related to the problem I'm having and the problem is still there, The problem which is at about 60-100 km, while driving the rpm's will bounce forward and back/flutter/surge. What I do is let off the gas and problem goes away/ or accelerate and problem goes away. From my understanding it may be one of two problems but I could be wrong, one is which is the TC, later 4T45Es have a PWM (pulse-width modulated) torque converter lockup as opposed to an on/off solenoid. It's supposed to make TC lock undetectable. Just wondering do I replace the Torque converter or solenoid(TCC solenoid). Thanks
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Sunday, January 5th, 2020 AT 1:37 PM (Merged)
Tiny
CARADIODOC
  • MECHANIC
  • 33,916 POSTS
If the rpm is going up and down about 200 rpm, it likely is the torque converter unlocking intermittently. It will unlock when you press the brake pedal, in preparation for coming to a stop, when releasing the throttle, to allow you to coast longer when slowing down, and under hard acceleration to provide more torque. Lockup only occurs above about 35 to 45 mph and when the engine is nearly fully warmed up.

First, when the problem is occurring, hold the brake pedal up with your foot. If the problem stops, readjust the brake light switch or be sure the pedal is returning fully. You can also verify the torque converter is unlocking by holding the accelerator pedal perfectly steady at highway speed, then very lightly holding the brake pedal down 1/2" with your left foot. The rpm should stay up at the higher speed and never drop back down. Don't use the brake lights to determine if the brake light switch is causing the problem. There's two or three different switches built into one assembly and the torque converter clutch can be on a different switch than the brake lights and cruise control.

The next thing is to connect a scanner to view live data and watch if the Engine Computer is commanding the torque converter to lock and unlock intermittently. If it continues to display lockup "on" while the problem is occurring, the cause is inside the transmission or the wiring to it. Normally a wiring problem will set a diagnostic fault code. Look at the coolant temperature sensor. If you have a temperature gauge on the dash, that uses a different sensor, so that is not relevant to this story. Ford had a lot of trouble with their Engine Computer coolant temperature sensors in the early '90s. They would make the apparent temperature bounce around all over the place and the computer would respond accordingly. That's very uncommon on most other cars, but not unheard of. On your car I would be more likely to expect to find a defective thermostat that is keeping the engine too cold, and it's right on the borderline of where torque converter lockup is allowed.

Don't overlook low fluid level too.
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Sunday, January 5th, 2020 AT 1:37 PM (Merged)
Tiny
SANDY
  • MEMBER
  • 2 POSTS
  • 1996 PONTIAC GRAND AM
  • 4 CYL
  • FWD
  • AUTOMATIC
  • 119,000 MILES
1996 Pontiac Grand Am. Engine Surges going primarily up an incline. Sporadic. Feels like I'm stomping on the gas pedal. I just changed out the Transmission filter as it seemed to be coinciding with downshifting to maintain speed going up hills. I was thinking Fuel Filter (it has been a while since I've changed it) however, I'm also thinking spark plugs, etc. Any suggestions? Thanks
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Sunday, January 5th, 2020 AT 1:37 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,885 POSTS
Has the check engine light ever come on? As far as the fuel filter, have you checked fuel pump pressure?

If it is the spark plugs, wires. Then it sounds like a misfire. However, that should have turned on the check engine light.

Let me know.

Joe
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Sunday, January 5th, 2020 AT 1:37 PM (Merged)
Tiny
SANDY
  • MEMBER
  • 2 POSTS
The check engine light has never come on. It doesn't sound like a misfire. No problems keeping the car running at idle. Only while driving. I don't have to be accelerating to have it '**** me' like mini-whiplash, however it's predominantly going up and incline and most prominent the steeper the incline.

Thanks!
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-1
Sunday, January 5th, 2020 AT 1:37 PM (Merged)
Tiny
LYNDAMCK
  • MEMBER
  • 1 POST
  • 1994 PONTIAC GRAND AM
Why do you think that my 1994 Pontiac Grand Am surges as I'm accelerating while riding on flat surfaces on cooler days (sub-50-degree days)? My mechanic mumbled something about "oil..." When I told him about it, but that's all I know. Thanks.
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Sunday, January 5th, 2020 AT 1:37 PM (Merged)
Tiny
CANVIS69
  • MEMBER
  • 131 POSTS
You probably have a air or coolant temp sensor that is stuck to high making you run lean. Otherwise it is probably a state of tune issue
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Sunday, January 5th, 2020 AT 1:37 PM (Merged)

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