Random Misfire problems

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HillHastey

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Getting into my car yesterday it would not start, turned over a bit then quit. Once it started it had an extremely rough idle, and check engine light came on. When in drive it doesn't shift gears very well and has a hard time getting any speed. I had the computer scanned and recieved the P0300 Random misfire code.

I've changed all the spark plugs out with new ones, which didnt help, then proceeded to change the coil pack; which decreased the rough idle, but did not fix the misfire problem.

I'm at a loss and don't want to keep throwing money at the problem.
 
HillHastey said:
Getting into my car yesterday it would not start, turned over a bit then quit. Once it started it had an extremely rough idle, and check engine light came on. When in drive it doesn't shift gears very well and has a hard time getting any speed. I had the computer scanned and recieved the P0300 Random misfire code.

I've changed all the spark plugs out with new ones, which didnt help, then proceeded to change the coil pack; which decreased the rough idle, but did not fix the misfire problem.

I'm at a loss and don't want to keep throwing money at the problem.
Click to expand...

Did you replace both coil packs or just one? And did replace the spark plug wires when you replaced the plugs?
 
Spark Plug Wires?

I was told that there are not any spark plug wires in a 2003 sunfire? I replaced the coil pack, and inspected the coils, which looked fine.

There was one spark plug that was toast, and another on the way - so I replaced them all. I have gone down through the extensive list of problems that could be the result of my misfire code but everything so far seems to be fine - except for the engine...still.
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HillHastey said:
I was told that there are not any spark plug wires in a 2003 sunfire? I replaced the coil pack, and inspected the coils, which looked fine.

There was one spark plug that was toast, and another on the way - so I replaced them all. I have gone down through the extensive list of problems that could be the result of my misfire code but everything so far seems to be fine - except for the engine...still.
Click to expand...


I'm not familiar with a 2003 since mine is a 98, but if it's anything like mine then it will have spark plug boots instead of the traditional spark plug wires. They look like this http://tinyurl.com/c7jdasq. They're called coil on boots, I think. But you said you inspected the coils, which are inside these boots so that may or may not be the problem.

Also, did you test the camshaft position sensor? Or inspect and clean your EGR valve (if your car has one)? Or the oxygen sensor?
 
I will have to take a look at those things next, once I have the time to put into it again! Bad time of year...

Mine has the coil boots as well, which I didnt see there was anything wrong with them. With a random misfire is there still a possibility of it being one coil causing the problem or would it have to be a part of the system that affects the entire firing process in more than one cylinder?

I'm assuming that there is a problem with more than one because I have complete lack of power in the first gear. Once it gets going into second gear it will pick up speed ok, but wtill pretty slow. I dont know if that points to a specific problem or not?
 
On the list you were given, the catalytic converter is a cause. Have you tried disconnecting it temporarily and seeing if the problem is resolved?
 
When I was doing my research, it was said that if the cat converter was the problem that there would be a bad smell coming from the exhaust, but it smells more like unburned gas then 'rotten eggs' as it was said to.
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HillHastey said:
When I was doing my research, it was said that if the cat converter was the problem that there would be a bad smell coming from the exhaust, but it smells more like unburned gas then 'rotten eggs' as it was said to.
Click to expand...

I've heard exactly that but when my cat was clogged up on my 96 and causing a misfire, I didn't smell a change in the exhaust coming from the car. What I did, was unbolt two of the bolts in front of the cat to let the exhaust escape until I could fix it. But, running my car with an unbolted cat majorly decreased the fuel mileage and also made the car sound like a ricer (which I kind of liked the sound). To fix it, instead of replacing the bolt on cat (which was around 110+), I put the front of the car on jack stands and crawled underneath the car. Unbolted both sides, took off the cat and rammed a crowbar down the center of the cat repeatedly in order to break up all the honeycomb. Once done, empty out all the broken up honeycomb.

Doing that is pretty much the same as running a straight pipes back to your muffler. I was also told by an employee at O'reilly that that would increase the gas mileage, but I'm not sure if it really did.
 
Also, if it's the original cat then the bolts will be very very stuck. Soak them in PB blaster first. And you also might break some of the bolts off, which is what happened to me.

And, replace the cat. converter gaskets with new ones once done.
 
HillHastey said:
Getting into my car yesterday it would not start, turned over a bit then quit. Once it started it had an extremely rough idle, and check engine light came on. When in drive it doesn't shift gears very well and has a hard time getting any speed. I had the computer scanned and recieved the P0300 Random misfire code.

I've changed all the spark plugs out with new ones, which didnt help, then proceeded to change the coil pack; which decreased the rough idle, but did not fix the misfire problem.

I'm at a loss and don't want to keep throwing money at the problem.
Click to expand...

Also, one simple thing to check is have your battery tested to make sure it has enough power to run the car.
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Decided to take it to a shop, they thought it was my cat but it turned out to be the ignition control module. Easy fix, but because of the unburned fuel I'm having problems with my emissions system working below threshold, and the downflow o2 sensor...CEL came back and throwing a P0420 and P0141.

I'm going to take a look at the sensor, see if its charred. I read that there was a way to clean them though? Would that work, or should I just shell out the $ for a new one?
 
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