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My 1997 Pontiac Bonneville will run fine for
Sent to Car Experts May 27 08:24 AM

My 1997 Pontiac Bonneville will run fine for about an hour and then it loses power and feels like there is no gas pedal even with it to the floor. It wants to stall and will occasionally backfire. It also pulls vacuum pressure from the A/C and air venting when speeding up. Could these be related problems? If I shut it off and restart it will run fine for a little bit and then the problem starts again. I am not showing any codes or check engine lights. Where might I start to look for the problem?

Customer (name blocked for privacy)
Status:  Closed   Value: $10
Info Request
May 27 8:49 AM (25 minutes and 23 seconds later)
         
REPLIED to Info RequestCheck Mark
Is the check engine light on?Does the transmission shift late or does it shift properly?



Master ASE Certified.L1 Advanced Engine Performance Certified.Pa Emission Repair Technician.Just Answer Car Category Mentor.
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Davo -- Master technician -- 99% Positive Feedback on 1931 Car Accepts
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Reply
May 27 9:18 AM (29 minutes and 10 seconds later)
         
Reply to Davo/diablo666's Post: No check engine light is on and the transmission seems to be shifting okay.
Customer (name blocked for privacy)
Answer
May 27 9:33 AM (14 minutes and 23 seconds later)
         
REPLIEDCheck Mark

Three things should be checked.Make sure the air filter or the path way to it is not clogged with debris.Check the fuel pressure during the failure the pump may be getting hot and slowing down.It could be as simple as a clogged fuel filter.The exhaust back pressure should also be checked.If the exhaust can't get out of the engine the engine vacuum drops.In bad cases it will cause late shifting to occur.You may even have a fuel pressure regulator leaking causing the convertor to overheat.That would be discoved when the fuel pressure is tested if you leave the gauge on for 1/2 hour.You could also pull the vacuum hose of the regulator to see if gas comes out.You may have to tap on it with a screwdriver handle to see it.



Master ASE Certified.L1 Advanced Engine Performance Certified.Pa Emission Repair Technician.Just Answer Car Category Mentor.
Picture
Davo -- Master technician -- 99% Positive Feedback on 1931 Car Accepts
ASE Master Technician/Advanced Automotive Diagnostic Technician
Reply
May 27 9:46 AM (13 minutes and 23 seconds later)
         
Reply to Davo/diablo666's Post: Would exhaust backpressure cause suction in the valve covers on the oil filler cap? I do not remember having suction on the filler cap before and it is doing that now. If I remove it with the engine runnung, it is held on by suction and I need to use force to remove it. Is that normal?
Customer (name blocked for privacy)
Answer
May 27 10:31 AM (45 minutes and 25 seconds later)
         
ACCEPTEDCheck Mark
Some body changed the pcv valve didn't they?The o-ring that goes on the bottom of the pcv valve is missing or you have bad intake gaskets.When you check the pcv valve there should be a large ring on the cap and a smaller one around the bottom of the lip on the pcv valve.Here is a picture you need to remove the plastic cover on the top of the engine. Images available only to Customers.



Edited by diablo666 on May 27 2006 at 10:34 AM

Master ASE Certified.L1 Advanced Engine Performance Certified.Pa Emission Repair Technician.Just Answer Car Category Mentor.
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Davo -- Master technician -- 99% Positive Feedback on 1931 Car Accepts
ASE Master Technician/Advanced Automotive Diagnostic Technician
Reply
May 30 8:25 PM (3 days and 9 hours later)
         
Relist: I still need help.
Should fuel pressure change after a my 1997 Pontiac Bonneville with a 3.8L engine and the K vin is idling for longer than a half hour? If so, what should fuel pressures be at startup and after a car is idling for a half hour, approximately? My car starts at about 47 psi and then drops to 24 psi after a half hour of idling. Is this normal?
Customer (name blocked for privacy)
Answer
May 30 9:12 PM (46 minutes and 58 seconds later)
         
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