P0301 misfire Scan tool diagnos help - Third Generation Forum

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P0301 misfire Scan tool diagnos help
Monday, January 28, 2013 7:29 PM
Hey guys I have a misfire in cylinder 1 i've had the compression tested and its fine, I got a new ignition coil for it and I got 4 new plugs and I still have this cylinder one misfire that i can't get rid of. Now I can also say that I have a high voltage reading on my post cat O2 sensor and its thowing codes as well. I want to get this misfire fixed so that I can be firing on all cylinders, I have a scan tool that shows live data from the engine. What could I look for when reading the live data from the vehicle to check for cylinder one misfire that would be able to lead me to the problem. I also got some fuel injector cleaner incase the injector may be clogged or something... anybody got any ideas? When I first crank it up and drive it ( because its been cold ) I can kinda feel the car skip slightly as if the power is cutting out but its kinda minor.... I just need help guys.

Re: P0301 misfire Scan tool diagnos help
Monday, January 28, 2013 7:57 PM
First move your injectors around and see if the misfiring cylinder moves with the injectors.

What kind of plugs did you get? Our cars only like NGK or ACDelco.

If your getting a p0420 that means your cat is screwed and it may be causing the issue as well.

A compression test wont tell you everything about cylinder condition and really a leak down test is best in these situations.
Re: P0301 misfire Scan tool diagnos help
Tuesday, January 29, 2013 5:17 AM
I had turned off the check engine light yesterday so it hadn't threw it again yet but I read the code anyway and not its saying P0300 random misfire. It usually always reads P0301 but every four times i reset the code and it comes back it will give me the random misfire instead of the cylinder one, but i was thinking that could be because I have an Acutron scanner but if this is happening what could this be a sign of
Re: P0301 misfire Scan tool diagnos help
Tuesday, January 29, 2013 5:33 AM
I typically get p0300 but the odd time ill get p0304.

Like I said before move your cylinder 1 injector and see if the misfire moves to there. Check all your engine grounds, take them off and clean under them and re tighten.

Then come back with the results.
Re: P0301 misfire Scan tool diagnos help
Tuesday, January 29, 2013 5:39 AM
Philly D wrote:

I typically get p0300 but the odd time ill get p0304.

Like I said before move your cylinder 1 injector and see if the misfire moves to there. Check all your engine grounds, take them off and clean under them and re tighten.

Then come back with the results.


x2 on everything said above.


"In Oldskool we trust"
Re: P0301 misfire Scan tool diagnos help
Wednesday, January 30, 2013 3:45 PM
guys not trying to sound lame but how do I remove the fuel railing to remove the injector
Re: P0301 misfire Scan tool diagnos help
Wednesday, January 30, 2013 6:14 PM
Well...

Knowing what engine we are talking about will really help us tell you.

It should be very easy and similar though on all models. Unbolt the rail and pull the rail and injectors out all at once.
Re: P0301 misfire Scan tool diagnos help
Thursday, January 31, 2013 4:16 AM
ecotec engine
Re: P0301 misfire Scan tool diagnos help
Thursday, January 31, 2013 5:38 AM
So undo the 2 bolts by the valvecover and pull
Re: P0301 misfire Scan tool diagnos help
Tuesday, February 05, 2013 6:44 PM
okay guys I moved the injector to cylinder 3 and sure enough the car is screaming cylinder 3 misfire. I noticed when I took the rail off every injector came out if the block but that one in cylinder 1 that I swapped to 3. The top O ring had a kinda scrape on it and it was loose in the fuel rail so I put a new o ring on top and put it back in cylinder 3 and bolted it back up. Now its misfire cylinder 3 and i noticed after everything was bolted back up I can still spin that injector..... but I put a new o ring on it so what the hell!
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