2003 Pontiac Bonneville 2003 Pontiac Bonneville ssei surgin

Tiny
HENRYAJ
  • MEMBER
  • 2003 PONTIAC BONNEVILLE
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 35,000 MILES
I have a ssei that is all of a sudden having the boost sensor fluttering and acts up more after the car has really heated up. The majority of time the boost sensor reads in the negative zone, but under acceleration the boost values will go over 0 to the positive side of the gauge. During the moments of fluttering, the sensor will go all from near red line of overboost to max negative and back. The engine rpm is affected enough that the engine will die at a stop, but the engine always restarts. It seems to really act up after the car has been operated awhile and really hot. The local repair shop has replaced the boost solenoid, but the problem continues. Any thoughts or actions would be appreciated.
Saturday, July 31st, 2010 AT 8:06 PM

7 Replies

Tiny
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Before I go further.
Are any codes stored in the computer?
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Monday, August 2nd, 2010 AT 8:40 AM
Tiny
HENRYAJ
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The shop did not say any codes were found. I would trust they would tell me if they had.
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Monday, August 2nd, 2010 AT 9:43 AM
Tiny
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I would not assume that, but you would know better than I.

Thr pcm disables the boost when:
When reverse gear is selected
When the vehicle is decelerating
When the engine coolant temperature is excessively high
When drivetrain abuse is detected.

If not codes are shown I would want to verify the coolant temp sensor is reading correct based on the symptom you have. If the coolant temp is excessively high then there may be the source.
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Monday, August 2nd, 2010 AT 10:19 AM
Tiny
HENRYAJ
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The temperature sensor may be the link. The engine does not have this problem at cold engine status. This problem comes into play after the engine has been running for awhile and certainly while stopped in traffic. The ambients also are adding to the issue here in Houston. The ambients are of course in the high 90's.

But if the engine temperature was at fault, would the coolant gauge on the dash report high temperature? The gauge on the dash is not reporting hight temps. (200 F).

The question I have is where is the temperature high enough to cause the pcm to be erratic. But why would the boost sensor cause the engine to flutter like that. I could understand if the pcm senses high temp then it would turn the boost solenoid on all the time.

Second question. Where should the boost gauge be at idle (no load)?
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Monday, August 2nd, 2010 AT 10:49 AM
Tiny
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I don't have that spec, but can offer this that may help.
RESULTS OF INCORRECT OPERATION
An open boost control solenoid control circuit, an open ignition 1 circuit, or boost control solenoid valve stuck open will cause reduced engine power, especially during wide open throttle operation. The boost control solenoid control circuit shorted to ground, boost control solenoid valve stuck closed or a restriction in the boost source or signal hoses will cause full boost to be commanded at all times and a possible overboost condition during high engine load situations. A restriction in the vacuum signal hose to the bypass valve actuator or a stuck closed bypass valve will cause a rough idle and reduced fuel economy.

There are two coolant temp sensors/switches. One for the gauge and a separate one for the pcm. What I am saying is to make sure the actual temp is true that the pcm is reading. This is done with a scanner for the pcm.
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Monday, August 2nd, 2010 AT 1:54 PM
Tiny
HENRYAJ
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Do you think a coolant temp sensor would cause the boost solenoid to act erratically. Or does this sound like more of an electrical problem (open to short to open)?

Where on the engine is the location of the coolant temp sensor for the PCM? Is there a way to fool the sensor temperarily to check it. Like if you unplugged it and ran the vehicle. Just looking for some simple things I can check without a scan tool.
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Monday, August 2nd, 2010 AT 3:08 PM
Tiny
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IT absolutley may be electrical. I don't know that it is or is not related to the boost nor the coolant temp. Frankly I don't see many SC.

By the sounds, the sensor was diagnosed before it was replaced. Is the sensor defective or was it mis-diagnosed? Or was it out of spec and was a part of the problem?

I would suspect a code being set if it was a coolant temp related situation, but it may not always set one.

When I think of hesitation, or stall when hot I don't think of boost. I first think of fuel. I would want to put a gauge and run it to the windshield to monitor the pressure when the problem occurs. Ideally I would have a scanner to take a snapshot of what is happening in the data stream.
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Monday, August 2nd, 2010 AT 8:38 PM

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