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1996 Grand am multiple cylinder misfire


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boomer0711
10-13-2003, 06:58 PM
The computer code on my Grand am comes out as multiple cylinder misfire. Sometimes the light goes off and sometimes when it comes on it is blinking. The car has tons of miles on it. The motor is the 3.1 v6 The car runs fine when it wants. Sometimes you can feel it mising out when your going down the road. Sometimes it acts like it's going to die when it's in park and it hesitates when you give it gas. The following is what I have replaced so far.
1 plugs
2 wires
3 coils
4 throttle position sensor
5 Mass Air Sensor
6 air filter

I fixed two vacume leaks and cleaned the throttle body if anyone can please help with this problem it would be great.

Ares78
10-14-2003, 12:47 AM
check your housing assembly to make sure there isn't any burn marks anywhere, and you might want to check your ignition module as well. I had the same problems at one point, and after i basically replaced the entire ignition system, it was ok.

Its also possible it could be a fuel problem....check your pressure as it could be a fuel pump or injector gone bad.

GMMerlin
10-14-2003, 07:09 AM
A binding fuel pump causing low fuel pressure will cause the problems you describe.
Install a fuel pressure gage and drive the vehicle until it starts misfiring and see if the fuel pressure drops.

boomer0711
10-25-2003, 09:28 PM
I finnaly got time to take the motor apart and :banghead: :banghead: checked the fuel injectors. Two injectors were shot and allowing fuel straight through. I replaced those and put on the old coils and throttle position sensor. I had to return those to pay for the injectors. Well the check engine light is still on but I haven't reset it yet either. Now occasionally when I hold the pedal to the floor the check engine light begins to blink. I have counted 11 and 16 blinks. Is this trying to tell me something or do I need to have a computer hooked up to it? Also the car seems to idle very low and rough. Could this be caused from putting the old throttle position sensor on?

Ares78
10-25-2003, 10:48 PM
Very well could be, my car was having the same kind of problems and a quick changeout of the throttle position sensor fixed it, but definately get a OBD scantool to make sure the exact codes the computer is giving you and go from there

GMMerlin
10-26-2003, 08:10 AM
The SES light is blinking because the PCM has seen a misfire count that will cause catalyst damage to the converter.

boomer0711
10-26-2003, 08:41 AM
I am definatly lost now. The car has so many miles it's not worth taking to the mechanic. Is there anything that I can check that may be causing this?

boomer0711
10-27-2003, 04:03 PM
Ok still having trouble with this damn car. It's starting to drive me crazy. It's not worth taking to the shop with all the miles on it. I do have one question I don't know which part it is so I will try to describe it the best I can. There is a sensor bolted where the bracket for the coils go. it has to lines going to it and an electrical connector. One line i vacume line I think comes off of the egr valve and one goes around the engine behind the coolant resevoir and down to the tranny I think. Anyways When the engine warms up it starts to make noise. The best I can describe this noise is like the rubber seal inside is popping letting air out. Does anyone know what I am dealing with. I also thank everyone that has tried to help me with this problem

GMMerlin
10-28-2003, 07:27 AM
If it is behind the coils and has a 2 wire connector, that is the Evap soleniod.
If it is infront of the coils mounted on its own bracket and has a 3 wire connectorits the MAP sensor.

Understand that it is difficult to diagnos a car over the internet.
If you can hold the pedal to the floor and the fuel cut-off doesn't kick in (around 4000 rpm) then that might be why the light started flashing.
You will need a scan tool to set fuel cut-off.

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