Help with code P 0300(engine misfire detected)
Thread Starter
Instructor
Joined: Oct 2010
Posts: 140
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Help with code P 0300(engine misfire detected)
2003 Zo6 with A&A P1sc, otherwise stock. Car runs great but this code always comes up. I clear it while driving and a few minutes later it comes back. This has happened since the supercharger was installed 6 years ago. I'm tired of clearing the engine light and code. Any suggestions? Thanks 
Tech Contributor
Joined: Dec 1999
Posts: 32,910
Likes: 2,402
From: Anthony TX
CI 6,7,8,9,11 Vet
St. Jude Donor '08
Well,,, Do you think that you have a misfire situation OR is it running fine???
If its running fine, you can have a tuner desensitize the misfire algorithm in the PCM.
The same thing can be done to the KNOCK Sensors if you have a BIG cam and the Knock sensors are giving false KNOCK info.
If its running fine, you can have a tuner desensitize the misfire algorithm in the PCM.
The same thing can be done to the KNOCK Sensors if you have a BIG cam and the Knock sensors are giving false KNOCK info.
Le Mans Master
Joined: Nov 2009
Posts: 6,882
Likes: 234
From: Bangkok, Thailand
I just got this code the last couple of days and it turned out to be a spark plug wire that split and was arcing to the header. With the blower you may not notice the miss, but the computer would still pick it up.
Tech Contributor
Joined: Aug 2008
Posts: 2,902
Likes: 21
From: Oak Hill Virginia
Do you still have your original plugs and wires? How many miles on your car? Has this been going on since your FI install or is it recent? Do you get your CEL only under load or at random irrespective of throttle or engine speed? Does your car run differently (rougher) when the P0300 dtc is set?
There are a lot of things that can cause a real missfire (plugs, wires, coils, injectors etc.) Start by checking your plugs and wires since that's the easiest.
The next time it happens have it scanned with an aftermarket scanner (free at most auto parts stores) so you know which cylinder to look at. The built-in code scanner on the C5 will not return individual cylinder codes like aftermarket scanners will, it just throws P0300. A scanner will read P0301 for cylinder 1 P0302 for cylinder 2 etc.
There are a lot of things that can cause a real missfire (plugs, wires, coils, injectors etc.) Start by checking your plugs and wires since that's the easiest.
The next time it happens have it scanned with an aftermarket scanner (free at most auto parts stores) so you know which cylinder to look at. The built-in code scanner on the C5 will not return individual cylinder codes like aftermarket scanners will, it just throws P0300. A scanner will read P0301 for cylinder 1 P0302 for cylinder 2 etc.
Le Mans Master
Joined: Aug 2005
Posts: 5,375
Likes: 328
From: CA.
St. Jude Donor '13-'14-'15
As Bill says---1st recognise if indeed there is a real misfire or a false misfire---If real and you can hear or feel it missing--track it down and fix---If false--It is common with some mods to get false misfires---Have your local tuner or do a mail order tune and have them disable/desensitize the misfire tables --
Thread Starter
Instructor
Joined: Oct 2010
Posts: 140
Likes: 0
As Bill says---1st recognise if indeed there is a real misfire or a false misfire---If real and you can hear or feel it missing--track it down and fix---If false--It is common with some mods to get false misfires---Have your local tuner or do a mail order tune and have them disable/desensitize the misfire tables --
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Racer
Joined: Oct 2001
Posts: 345
Likes: 8
From: Palatine Illinois
The computer detects a misfire by using the crank position sensor. If you lighten or otherwise load the crank in a not normal way (for example, using a lightweight clutch, U/D pulley) the sensor senses the crank in a place that it didnt expect and thus causing the misfire code to go on.
if you think the car is running fine and there are no issues, like wires/plugs, you can desense the misfire detection through a tune.
if you think the car is running fine and there are no issues, like wires/plugs, you can desense the misfire detection through a tune.
Thread Starter
Instructor
Joined: Oct 2010
Posts: 140
Likes: 0
Code P 0175
The computer detects a misfire by using the crank position sensor. If you lighten or otherwise load the crank in a not normal way (for example, using a lightweight clutch, U/D pulley) the sensor senses the crank in a place that it didnt expect and thus causing the misfire code to go on.
if you think the car is running fine and there are no issues, like wires/plugs, you can desense the misfire detection through a tune.
if you think the car is running fine and there are no issues, like wires/plugs, you can desense the misfire detection through a tune.
