Random misfire

05-01-2007, 09:01 AM

I have a 2000 Alero, 2.4L.

It is misfiring bad. My roommate has changed the spark plugs and coil tower. Next are the coils. I also noticed I have a bad oil leak there is leaking on my plugs. Before I just keep throwing money at it, what else should I check? I don't know much about cars and I don't really have the money to take it into a shop, so I just have my buddy working on it when he has the time.

thanks!

p1mptress · 05-01-2007, 12:18 PM

Ok what is misfiring? B/c I think it might be happening with my car when you hit the gas and the rpm go up and down and up again? Just wondering if I have the same problem to. Sorry for posting on your thread!

alerored04 · 05-01-2007, 12:21 PM

try the fuel filter, easy fix if you have a jack. Check all the wiring on your throttle body and mass airflow sensor. Make sure the mass airflow sensor is installed in the correct direction. Otherwise maybe a fuel pressure regulator? Are you sure its oil on the plugs and not fuel or fuel and carbon build up? Also, is it throwing a code? As in service engine light? If so go get it scanned, that might help us figure it out.

05-03-2007, 08:43 AM

My room mate scanned it, and it's coming back with Random Misfire & my O2 sensor needs replacement, the second O2 sensor to be specific.

I don't really have the cash to take it to a dealership to have it scanned. We're gonna try replacing the coils today and if that works, then awesome, if not then back to square one.

05-03-2007, 09:52 AM

Quote:

Originally Posted by dustin

My room mate scanned it, and it's coming back with Random Misfire & my O2 sensor needs replacement, the second O2 sensor to be specific.

I don't really have the cash to take it to a dealership to have it scanned. We're gonna try replacing the coils today and if that works, then awesome, if not then back to square one.

The O2 sensor could be contributing to the misfire. If the sensor isn't reading right, the computer doesn't know the proper ratio in which to mix the fuel and air. I still don't think this alone would cause a major misfire, but it could be a contributing factor.

alerored04 · 05-03-2007, 11:42 AM

not if its the downstream o2. The only reason that one is there is to tell the computer the cat is working properly. If its the upstream sensor then that is a major contributor to your missfire. But if its the downstream thats bad which from your post it seems to be, i think that irrelevant. Take the coil packs to autozone, the know the voltage drops for them and can test them for you without having to buy new ones. Good luck. And a random missfire could likely be a fueling issue. Im telling you change the fuel filter, they cost like $8 and are fairly easy to do.

NeonStatus · 05-04-2007, 01:56 PM

I too have a misfire but in cylinder one on 3400 engine. I have just replaced MAF sensor, plugs, and wires. I heard it could be either clogged #1 injector or a head gasket. I need to get this fixed to pass emissions and cannot bring it to the dealership or a shop to get it fixed. I didn't want to start another thread since this pertains to the topic. Does anybody have any ideas on how to figure out what is causing the misfire?

alerored04 · 05-04-2007, 03:06 PM

i would definately check the coil on that one. If its a localized miss it should be caused by something related to that cyl. Injector is a good idea if you are capable of changing it yourself that might be a good idea. Best way to check if the coil is causing the problem, take the coil pack for cyl #1 and which ever other cyl is on the same pack and switch it with a different pack. If the miss follows the #1 coil pack to the new cyl its on you know its the coil. If the miss stays on #1 your next best bet might be a new injector or maybe just run some seafoam through it. Just be sure to remember which coil goes where and which wire goes where when you are mix and matching like that.