Mechanics

GT PROBLEMS

2002 Pontiac Grand Am • 6 cylinder FWD Automatic • 150,000 miles

The car seems to have no power. It seems like when you step on the gas you don't have A positive response. I get no faults on the code reader Car has nkg plugs and bosch wires. That are not that old. I have read that you should use AC plugs.I did have A plug wire fault the light then quit on its own Car starts and idles smooth Car seems worse when it warms up
This car seems to stay in gear till you let off gas even with regular driving in first and second gear you have to let off gas to get it to shift once the car is warm. With all the sensors its hard to tell whats not working. Both map and tps test out fine. When you shut motor off when hot the car makes A loud pinging noise from under the hood









When I say no power I mean its not smooth like when it was running right.I can get up to 70 MR but its not smooth. If I push harder on gas it will climb up fast but will not change gears till I let of gas A little. When Crusing at 70 MPH the trans and motor wont work together If I step it down it reves up before catching. At slower speeds it bogs before catching.
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Dazieff
May 18, 2011.



The first thing I would check is your back pressure sounds like you have a restricted exhaust. Possible a plugged cat let me know what you find on the back pressure.

Saturntech9
May 18, 2011.
How do I check back pressure

Tiny
Dazieff
May 19, 2011.
With a back pressure gauge you would unscrew the o2 sensor in one of the exhaust manifolds screw the gauge in and run the rpms up to about 2000 rpms and watch the gauge to see what the reading are. The put the sensor back in and do the same thing on the other manifold. Or you can take it to a exhaust shop and have them test it.

Saturntech9
May 19, 2011.
I hooked A vac gauge to port on intake manifold. Warmed engine recorded readings. Ran engine to 2000 RPM 4 times recording readings, The Idle reading was 18. All 4 other readings were 18. The gauge would drop to 16 for A second and reset at 18. Could this problem be A oxygen sensor as car operates perfectly till it warms up. Oxygen sensor don"t work till the temp rises or am I in left field Thanks Dazieff

Tiny
Dazieff
May 19, 2011.
The best way to check for excessive back pressure is to use a back pressure gauge in the o2 sensor hole of the exhaust manifold. Usually a o2 sensor when it goes bad won't cause that great of a power loss. When you get a plugged get it gets worse when the engine is warmed up because everything expands and restricts the exhaust even more. Also a plugged cat will cause the car to not shift till you let up on the exhaust.I would check the back pressure to rule that out first.

Saturntech9
May 19, 2011.
You were right. Checked cat poor reading put on new Cat. Car runs like new Thanks dazieff

Tiny
Dazieff
Jun 2, 2011.
Your welcome had a feeling thats what it was glad to hear you got it fixed.

Saturntech9
Jun 3, 2011.