adithius

I've been misfiring and I cant pinpoint what part to change.

The car misfires when I floor it and the revs go above 4000 RPM. Also I've been hearing some misfires when the car is idle (these are very suddle). The car also feels like it is jerking at times (comming from the front of the car).

I checked the ECU. It read 0505. Meaning no problems.

I can say that it is either the spark plugs, fuel injectors, or the ignition coils. I dont know which of them. Maybe even a sensor?

I tested the ignitions coils like this:
While the car was one, I disconected the plugs to each ignition coil one by one, and I can hear that engine loses power when I do this. So I think it may not be the coils, but I could be wrong.

How do you test the coils for sure? Same goes for the spark plugs and fuel injector. How do you check them?

What do you think might be the problem?

Thanks for the help in advance. It sucks when a Saturn is competativly racing with me on the street because my engine misfires.

KMax2988

Try resetting the ECU before you do anything first? I know it sounds retarted but my car had a misfire problem about 5 months ago. After going through the car's wiring, checking coils and plugs, etc; I found that cylinder 1 was the culprit. To my surprise, after replacing the coil it would still misfire. In a final act of desperation I ended up unplugging the battery for a day and its been running fine ever since. Hope this will help ya.

Adrian112597

iTrader: (1)

First unscrew all of the screws on the coils, then with the car running pull off one coil pack at a time until the misfire stops.

Adrian112597

iTrader: (1)

That will tell you which one is bad, if it is a coil pack

Adrian112597

iTrader: (1)

One more thing, on my 95 it wasn't the coil pack it was the injector that was bad. To test those, get a ohm meter and they should ohm out around 12 ohms average +/- a few ohms. If one of them seems extremely high compared to the others, thats the bad one

adithius

I had tried this already. The plugs all seem to charge the cylinder. The misfires dont happen all the time.

KMax2988

Same thing that happened in my situation which made it hard to determine which one was misfiring. Was only able to find it when it was misfiring at idle one day; went around unplugging coils one by one till I found the one that didnt make the misfire worse. To confirm I unplugged all the coils, pulled out and plugged in the one I thought was bad, put the spark plug on the end of it and placed the electrode up against a piece of metal, then turned the car over while checking for spark (no spark, tried different plugs on it as well). Like I said before though, even after replacing it I still got a misfire in that same cylinder (checked continuity between all the coil and injector signal wires and the ECU as well as a few other things). It only went away after resetting the ECU.

I30tMikeD

iTrader: (8)

it is very possible to get a bad misfire and not get a CEL, happend to me a few times. One would think the ECU would throw a code right away but things don't always work out so perfectly. Pulling each coil while the car is running is a good way to check, and if no change occured when the coils were disconnected then I would move on to the injectors. You can either check the ohm resistance on each one, or use a screw driver or a mechanics stethescope (sp?) to listen to each one. They should tick really fast. If one sounds different than the others than it could be your culprit. The middle one on the rear bank is hard to get to without removing the manifold though. Also pull the plugs and see how the look

maximabebe

iTrader: (24)

If you have no luck with the coils, then I would say to double check each injector to make sure that they are fully pressed down and "clicked" into place. I had a similar problem and could not figure it out for the life of me so one day I randomly checked to make sure the injectors were properly seated and my cylinder one injector hada lil play in it so i pushed it down and it clicked into place. The difference was like night and day. By the way, do you have a put put sound from the exhaust while idling?

adithius

Thanks Maximabebe. It's more like a hesitation on the whole car, or thumping. Yes I can hear the exhaust hesitate too.

Nealoc187

iTrader: (23)

Sounds like bad coils to me. Just because a coil works fine at idle doesn't mean it works fine at WOT above 4000rpm. I'm willing to bet money it's your coils. Your problem is identical to the problem I had. No misfire code, but horrible misfiring, couldnt go above 3500rpm at WOT. Car idled absolutely perfectly. I replaced all my coils and the problem is totally cured. It's your coils.