97 Grand am, random multiple cylander misfire

I have a 97 grand am 2.4L manual with about 160k miles on it and a weird problem.

I can start my car, and she will idle perfectly. In fact, I can reverse out of the drive and go about 20 feet fine. And then it will randomly start to misfire, and I get a code of P0300 (its always P0300) and I have to keep my foot on the gas or it dies. This only ever happens when its below about 50F outside, and the car has been off for about 6 hours. After about half a mile of reduced power and a very bumpy ride, she's warmed up a little, and runs great.

I've put in brand new spark plugs, no dice. I'm planning to go to the junk yard this weekend and will pick up some other things to try, but I need to know what I should grab? Coil pack(s) (how many does this car have?). Vaccume tubes? etc?

Here's a screen grab of the code. Help? Suggestions? What do I do :biggrin:?
http://tinypic.com/view.php?pic=21kz60n&s=4

Welcome to AF!!

The coils are a good place to start, you should have 2, but so are the connectors (boots) that attach to the plugs. These can go bad and since they carry the voltage from the coils to the plugs if they are cracked or just worn out as yours may be they will give you the performance issues that you indicate.

Alrighty! Sorry for the late response.

I picked up a 4pack(I think thats what it was called?) and boots for the spark plugs from the junk yard, engine ran exactly the same.

Checked my O2, air intake temp, and manifold pressure sensors, all working correctly.

I read somewhere that my problem could be an issue with egr flow valves?

Other ideas?

Check the injectors to make sure they are working properly. With your mileage it is possible that they are worn to the point where they are not responding properly to the ECM. Also check to make sure you have good fuel pressure. You may want to get a noid light a the local parts store to check the injectors. It could also be the wiring to the injectors causing the problem.

As for the EGR it can cause misfires but usually random misfire are due to ignition related issues. You can remove the EGR and clean it with throttle body cleaner.

disconnect main O2 sensor the one that controls AF ratio, drive your car and see if it works better if yes then you have lean condition which means not enough gas is getting in due to dirty injectors.

disconnect main O2 sensor the one that controls AF ratio, drive your car and see if it works better if yes then you have lean condition which means not enough gas is getting in due to dirty injectors.

Tried that this morning and the car ran great! Now my only question is how do I go about getting them cleaned?

buy re manufactured package of injectors, that way they will be much cheaper you will save yourself some money in the long run.

There is a way to have them professionally cleaned. Most oil change shops can do it or you can take it to a mechanic. The cost is about $50-75 to get it done. This would be cheaper than injectors but with your mileage reman injectors may be the way to go.

Update! (My problem still exists :banghead:)

I got my injectors professionally cleaned at the local oil change shop, wasn't too bad at 60$. I don't know if they did a noid light check or not. Either way, I'm getting some better gas mileage, but the engine still misfires. If anything it's worse!

I used to be able to stomp on the gas and at least keep it alive, but now it dies and I have to spend 2 minutes cranking and stabbing the gas pedal to get it started again (which it then runs just fine!).

I'm beginning to think it might just be cheaper/easier/better to sell the car :rolleyes:. But I'll try a few more things before resorting to that. Ideas?

Update! (My problem still exists :banghead:)

I got my injectors professionally cleaned at the local oil change shop, wasn't too bad at 60$. I don't know if they did a noid light check or not. Either way, I'm getting some better gas mileage, but the engine still misfires. If anything it's worse!

I used to be able to stomp on the gas and at least keep it alive, but now it dies and I have to spend 2 minutes cranking and stabbing the gas pedal to get it started again (which it then runs just fine!).

I'm beginning to think it might just be cheaper/easier/better to sell the car :rolleyes:. But I'll try a few more things before resorting to that. Ideas?


I don't trust those cleaning machines unless you do the cleaning process 3-5 times in the row.

that is why I said buy re manufactured injectors to save yourself some money in the long run. They are cleaned and internal parts are new, re manufactured pack of 4 would be around 100$ but you don't' want to listen.

may want to see if your intake gasket is leaking, you can spray starting fluid around the engine while its running and if your rpms rev in a certain area that indicates a leak.

may want to see if your intake gasket is leaking, you can spray starting fluid around the engine while its running and if your rpms rev in a certain area that indicates a leak.

I sprayed around, however I didnt hear a change in rpms at all.

But I have some updates.

It is now starting to die in the middle of driving, about 20 minutes in. Randomly the rpms will drop below 500 for about 2 seconds, and if I dont hit the gas it'll die - and then I have no breaks or power stearing (aint that scary thought, but I usually drop down to 15-20, second gear, let off the clutch and bring it back). A mate of mine thinks it might be the fuel pump?

However! The other day I was refilling the coolant for the 3rd time in the past two months and decided to check if there was a leak. I found the old owner had glued shut the weep hole! Besides needing a new water pump, could this also be causing my problem?

If the car ran good with the 02 sensor disconnected, the injectors are obviously not the problem. i would start by checking with a scanner and see what the readings are on your sensors. If you have a faulty temp sensor, not temp sending unit, but temp sensor, it could cause a problem like this. Or if you have bad 02 sensor, it could cause this. Your vehicle has a heated 02 sensor to assist 02 sensor accuracy during cold starts. If this heater circuit not working correctly, then it would cause a cold running problem. I would look at the voltage output from the 02 sensors with a scan tool to determine if this is a problem or not. Sensors can read within range, but also be bad.

Also check fuel pressure to see if the fuel pump is working correctly. And to make sure the pressure regulator is working correctly.