HELP DTC Code P0300
Thread Starter
Instructor
Joined: Dec 2006
Posts: 155
Likes: 0
From: Central Valley CA
HELP DTC Code P0300
My 08 LS3 MZ6 suddenly started to run rough and a home scan shows this code.
P0300 Random/Multiple Cylinder Misfire Detected
I've checked the conections on both sides of the coils and didn't find anything loose.
My LS3 has been forged and stroked and has the last gen A&A S-Trim by a local shop that has closed it's doors.
I know it has to go to a shop and there are several in my area with great reps. I'm looking for some input for the possible culprit.
Bad Fuel-It's only seen the great CA Chevron 91 octane
Loose connection
Did I break something?
P0300 Random/Multiple Cylinder Misfire Detected
I've checked the conections on both sides of the coils and didn't find anything loose.
My LS3 has been forged and stroked and has the last gen A&A S-Trim by a local shop that has closed it's doors.
I know it has to go to a shop and there are several in my area with great reps. I'm looking for some input for the possible culprit.
Bad Fuel-It's only seen the great CA Chevron 91 octane
Loose connection
Did I break something?
Melting Slicks
Joined: Aug 2006
Posts: 2,167
Likes: 11
From: Powell TN
Cruise-In VIII Veteran
That is where I am right now. Mine was running rough with a P0300 code. I pulled in the garage and did the same thing as you, pulling wires off and listening for a change in the idle and not really noticing any. I had logged with HPTuners, so I went in the house to go over that.
A couple of days later, I was going to change the oil in another vehicle. It was cold and rainy so I decided to back the vette out of the garage and pull the other vehicle in to change the oil in it. Well, it wouldn't start, no starter, nothing, just the lights came on. Really strange since I had started and stopped it several times when I parked it. I checked the codes and had a crank sensor code. I bought a crank sensor today, but didn't get a chance to put it in. I'll post back and let you know the results.
A couple of days later, I was going to change the oil in another vehicle. It was cold and rainy so I decided to back the vette out of the garage and pull the other vehicle in to change the oil in it. Well, it wouldn't start, no starter, nothing, just the lights came on. Really strange since I had started and stopped it several times when I parked it. I checked the codes and had a crank sensor code. I bought a crank sensor today, but didn't get a chance to put it in. I'll post back and let you know the results.
Burning Brakes
Joined: May 2003
Posts: 872
Likes: 0
From: Tucson AZ
My 08 LS3 MZ6 suddenly started to run rough and a home scan shows this code.
P0300 Random/Multiple Cylinder Misfire Detected
I've checked the conections on both sides of the coils and didn't find anything loose.
My LS3 has been forged and stroked and has the last gen A&A S-Trim by a local shop that has closed it's doors.
I know it has to go to a shop and there are several in my area with great reps. I'm looking for some input for the possible culprit.
Bad Fuel-It's only seen the great CA Chevron 91 octane
Loose connection
Did I break something?
P0300 Random/Multiple Cylinder Misfire Detected
I've checked the conections on both sides of the coils and didn't find anything loose.
My LS3 has been forged and stroked and has the last gen A&A S-Trim by a local shop that has closed it's doors.
I know it has to go to a shop and there are several in my area with great reps. I'm looking for some input for the possible culprit.
Bad Fuel-It's only seen the great CA Chevron 91 octane
Loose connection
Did I break something?
Racer
Joined: Jan 2008
Posts: 276
Likes: 0
From: Rothesay New Brunswick
P0300 can be a lot of things...ive had this on my Grand Prix...turned out to be a clogged cat. Things to check..
Plugs and wires
Coils
Check vacuum line connections
Checks for leaks around your injectors
Keep scanning after each drive to see if you get more codes (ie. cps)
Plugs and wires
Coils
Check vacuum line connections
Checks for leaks around your injectors
Keep scanning after each drive to see if you get more codes (ie. cps)
Instructor
Joined: Oct 2007
Posts: 106
Likes: 0
From: Prosser WA
If all else fails, you can go back to the old school and hook up a vacuum gauge. Look at it during idle:
1) reads very low, you have a leak
2) reads low and steady, late ignition (which you should see with HPTuner)
3) reads high and steady, early ignition (same as above)
4) neddle fluctuates as engine speed increases, ignition miss or valve spring
5) gradual drop in reading at idle, excessive back pressure
6) intermittent fluctuation at idle with good vacuum, ignition miss
7) stead from 17-22 in Hg, your are right on!
Just some ideas to look at, there might be more ways to interpret a vacuum gauge, but that is all I can think of...
1) reads very low, you have a leak
2) reads low and steady, late ignition (which you should see with HPTuner)
3) reads high and steady, early ignition (same as above)
4) neddle fluctuates as engine speed increases, ignition miss or valve spring
5) gradual drop in reading at idle, excessive back pressure
6) intermittent fluctuation at idle with good vacuum, ignition miss
7) stead from 17-22 in Hg, your are right on!
Just some ideas to look at, there might be more ways to interpret a vacuum gauge, but that is all I can think of...
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