'01 Malibu Tranny or Fuel Problem?

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  #1  
Old 09-04-08, 07:28 PM
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'01 Malibu Tranny or Fuel Problem?

My '01 Malibu with 197,000 miles has been developing a strange performance problem over the last 2 years and now getting worse.

When at highway speeds with slight acceleration the car pulses/surges (speeds up, speeds down) feels like someone is feathering the gas pedal up and down.

Could be fuel regulator or slipping trans.........?
Maybe tranny pump going?

The fuel pump and filter have both been replaced in the course of the last two years but has had no effect on this problem.

If I stand on the throttle from a dead stop the car does it severly.

The tach does fluctuate about 200 to 300 rpms during the pulse/surging at highway speed. The rpms are even farther apart during faster accellerations.

Does anyone have any real life experience with this problem?
 
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  #2  
Old 09-05-08, 06:07 AM
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Surging is pretty common, especially as things get a little more worn and along in years/miles.

You may have a physical slippage in the drive train with the transmission or you may have the engine acting up.

The fuel pressure regulator would be a real possibility. Run the engine for a short time, shut it off. Then turn on the key for about five seconds, then off and back on for five seconds. Then, turn the key off and let it sit for about ten minutes. Then depress the schrader valve (looks like a little tire valve) on the fuel rail. You should get a little spurt of fuel. If you don't have any pressure at that valve, the regulator is a real suspect.


Air flow restrictions or fluctuations also can cause it. The fluctuations can be attributed to worn parts (valves, timing chain, ignition - distributor, when applicable). Also vacuum leaks around gaskets, hoses, connections cause that type of "hunting). Another possibility is the idle air control device = valve or motor.

Essentially the idle air jobbies are device controlled vacuum leaks. When they work as designed - no problem. But when they act up you can get an erratic vacuum = surging.

Another possibility is the air conditioning compressor kicking on and off. I don't know about the Malibu, but some cars have an air control valve to step up the idle rpms for the AC. I think that would be a long shot, though.
 
  #3  
Old 09-05-08, 08:33 AM
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I have a 2000 Olds Alero that had 100,000 miles on it and it was acting similar to your Malibu. When there was a light load on the engine I felt it miss/slip, and I was sure the tranny was going out. I took it into a shop and they said I needed a tune-up. So I had them replace the plugs while they had it. And the problem was fixed.
If you haven't changed the plugs or had a tune up in a while it might be worth a shot.

Good Luck
 
  #4  
Old 09-05-08, 10:02 AM
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At 200,000 miles there would be a long list of potentially worn out parts. Probably time to get hooked to a scanner by a good mechanic.
 
  #5  
Old 09-05-08, 03:56 PM
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Originally Posted by jdawg View Post
I have a 2000 Olds Alero that had 100,000 miles on it and it was acting similar to your Malibu. When there was a light load on the engine I felt it miss/slip, and I was sure the tranny was going out. I took it into a shop and they said I needed a tune-up. So I had them replace the plugs while they had it. And the problem was fixed.
If you haven't changed the plugs or had a tune up in a while it might be worth a shot.

Good Luck
Been there, done that.
Very well maintained.
 
  #6  
Old 09-05-08, 04:00 PM
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Originally Posted by the_tow_guy View Post
At 200,000 miles there would be a long list of potentially worn out parts. Probably time to get hooked to a scanner by a good mechanic.

Yep....... you're right TG.

Ya know it's kinda like a dentist appointment.
You have to do it but just keep putting off.
 
  #7  
Old 09-05-08, 04:05 PM
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Originally Posted by marbobj View Post
Surging is pretty common, especially as things get a little more worn and along in years/miles.

You may have a physical slippage in the drive train with the transmission or you may have the engine acting up.

The fuel pressure regulator would be a real possibility. Run the engine for a short time, shut it off. Then turn on the key for about five seconds, then off and back on for five seconds. Then, turn the key off and let it sit for about ten minutes. Then depress the schrader valve (looks like a little tire valve) on the fuel rail. You should get a little spurt of fuel. If you don't have any pressure at that valve, the regulator is a real suspect.


Air flow restrictions or fluctuations also can cause it. The fluctuations can be attributed to worn parts (valves, timing chain, ignition - distributor, when applicable). Also vacuum leaks around gaskets, hoses, connections cause that type of "hunting). Another possibility is the idle air control device = valve or motor.

Essentially the idle air jobbies are device controlled vacuum leaks. When they work as designed - no problem. But when they act up you can get an erratic vacuum = surging.

Another possibility is the air conditioning compressor kicking on and off. I don't know about the Malibu, but some cars have an air control valve to step up the idle rpms for the AC. I think that would be a long shot, though.
I like your suggestions.
This re-inforces my theory that it can be fuel related especialy since a new trans could cost big bucks.
 
  #8  
Old 09-05-08, 04:10 PM
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I should also add that at least 2~3 times a week the idle jumps up to 2,200 to 3,500 rps all by itself and have to shut off the ignition and switch the key on and off several times to reset it.
 
  #9  
Old 09-05-08, 04:42 PM
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That could very well be the idle air control stuff.
 
  #10  
Old 09-06-08, 11:22 AM
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Would a bad throttle position sensor cause the idle to increase like that? I am pretty sure that I have seen that before
 
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