2002 Pontiac Sunfire Hesitates and bucks over 50mph

Tiny
MAX2361
  • MEMBER
  • 2002 PONTIAC SUNFIRE
  • 4 CYL
  • 2WD
  • MANUAL
  • 140,000 MILES
I'm having a semi intermittent problem where the car bucks and the engine severely hesitates when operating over 50 mph after running for a while. I used a bottle of Gumout fuel system cleaner 2 weeks ago and the problem seemed to go away. I commute 80 mile a day and it performed fine for over a week but yesterday the problem returned. I drove it to work this morning without any problem but it started again on the trip home after driving 35 of the 40 miles. I worked as a mechanic when I was younger, but had to give it up due to a back injury. A mechanic friend of my son said it might be the "coil tower". I've already purchased a fuel filter that I plan on replacing this weekend along with the spark plugs. This is our only vehicle and I don't have the money to take it to a mechanic. Any help would be greatly appreciated. Thanks in advance.
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Thursday, February 18th, 2010 AT 5:12 PM

3 Replies

Tiny
RASMATAZ
  • MEMBER
2002 Pontiac Sunfire Hesitates and bucks over 50mph

Inspect and test all the following listed below:

Oxygen sensors.
Catalytic converter.
Fuel injectors dirty/sticking.
Mass airflow sensor/Airflow meter.
Throttle position sensor.
Manifold absolute pressure sensor.
EGR Valve
Fuel pressure regulator leaking or defective fuel pump.
False air leakage.
Fuel contamination.
Foul/defective spark plugs.
Open spark plug wires.
Ignition coil/Coil packs defective.
Incorrect ignition timing.
Cap and rotor.

Note:If it doesn't apply disregard
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Thursday, February 18th, 2010 AT 5:15 PM
Tiny
MAX2361
  • MEMBER
The check engine light has not come on so that should indicate that there were no trouble codes generated and the sensors should be ok. Please correct me if I'm wrong. I have next to no experience working on this vehicle other than brakes & oil changes and I haven't done any major auto repairs in over 15 years so I don't have a diagnostic scanner. Giving me a list of 15 things to check with no other information doesn't really help. I can rule out fuel contamination because it will run fine for a while and then start hesitating with the same fuel. It also idles and runs fine up to about 50mph, so shouldn't that rule out several items on the list. I'm going to check everything I'm able to this weekend. I'll post the results of what I find and hopefully that will help narrow things down.
Thanks
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Thursday, February 18th, 2010 AT 5:43 PM
Tiny
SCOTTY DEE
  • MEMBER
Hi max2361. Do you own a fuel pressure gauge with a long enough line to connect it to the fuel rail and tape the gauge to the windsheild? I would like to know what the fuel pressure reading is at speed when it hiccups.
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Tuesday, February 23rd, 2010 AT 8:35 AM

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