Grand Am gt 2002 problems

DAZIEFF

MEMBER
2002 PONTIAC GRAND AM
6 CYL
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.

7 Replies

SATURNTECH9

MECHANIC
30,869 POSTS

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.

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Wednesday, May 18th, 2011 AT 11:55 PM

DAZIEFF

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How do I check back pressure

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Thursday, May 19th, 2011 AT 12:59 AM

SATURNTECH9

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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.

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Thursday, May 19th, 2011 AT 3:42 AM

DAZIEFF

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5 POSTS

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

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Thursday, May 19th, 2011 AT 5:01 PM

SATURNTECH9

MECHANIC
30,869 POSTS

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.