1996 Grand am multiple cylinder misfire

[boomer0711]

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.

[rixGAphx]

With high milage, the EGR system may well be plugged or have a stuck/broken valve.
i don't know that it would throw a multiple-cylinder misfire code.

Do a search to find the cleaning/replacement procedures, it's kind of involved.

Have you done a compression test? Kind of a biotch, since you have to remove those damned rear three plugs.

[boomer0711]

Thank You for the reply I will have to check on the things you mentioned first chance. As always I appreciate any kind of help mentioned.

[4kQuad]

did you gap the plugs or just put them in?

Are you sure you got all the spark plug wires on tight?

back in the right order?

Seem like simple questions, but a lot of times if it was not missing bad before you started........

So what was it doing to make you decide to chage all that stuff out any way?

[93GASE3300]

How many miles are there exactly.

[boomer0711]

there are 158000 miles on the car. Ever since I have changed the mass air flow sensor It has done much better. You can still feel it missing out going down the highway sometimes and when you first start it up it idles high. It starts much better and restarts if it dies. But the engine light is still on and I have the small problems.

[mikem220153]

You haven't mentioned whether you have checked the ignition control module or the cransahft postition sensor. These can cause multiple misfires as well.

[boomer0711]

I haven't checked either of those. The car is doing a lot better and starting all the time. The little problem I have now is after shutting down after a long trip. I go to restart it and then that is when it misfires.

[rixGAphx]

Have you checked/replaced the cat?

158k is enough to have totally fried and nearly plugged the cat. Lots of dirty backpressure may affect the O2 sensor's readings.

On the '96 3.1, there are TWO sensors for o2: One in the exhaust manifold at the engine, and another just aft of the cat.
The 'puter compares values from both, and kinda determines if the cat is doing its job.

Check out both O2's, and the cat.

-Rick

edit - See parallel thread for O2 sensor testing.

[boomer0711]

Thanks for the help I will have to take the car to an exhaust shop and have them check the converter

[boomer0711]

Ok the cat was fine. I tore the motor apart and 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?

[mikem220153]

The flashing Check Engine light indicates the computer is still detecting misfires. Do you have access to a scan tool to see what codes it is latching?

[boomer0711]

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

[mikem220153]

Boomer0711;

That is the Evap canistor purge solenoid. Here is a description of what it does and it's components: Evap system (http://www.cybrrpartspro.com/Chilton%20Manuals/9106m/9106CH04_12.HTML)