Just got the new throttle position sensor installed and the air intake all put back together. Still getting the P0300 code and engine is running a little rough. I'm at a loss now. Anyone have any ideas?
Just got the new throttle position sensor installed and the air intake all put back together. Still getting the P0300 code and engine is running a little rough. I'm at a loss now. Anyone have any ideas?
Going out on a limb here but on the Liberty's and on the Liberty forums, the 3.7 V6 has a problem of breaking valve springs, weak valve springs, etc. on valve springs. One of your Intake valve springs could be broken or worn so bad that the Intake valve isn't closing properly and could be throwing the miss fire code.
Of course that's a big if. How are your coils on each cylinder? Could one of some of them be bad causing the miss fire?
Last edited by criket; 06-02-2013 at 02:24 PM. Reason: Not thinking correctly, lack of sleep....
SOLD - 2005 | WK | Khaki | 3.7 | QT1 | OME HD Front Struts | Rusty's 2" lift in Rear w/ Monroe load levelers (F150 version) | 265/70 Nitto Terra Grapplers | 17" Moabs | 1.5" wheel spacers | Pinch weld mod | Rear fender trim mod | 4xG Matrix w/ reciever hitch | 4xG Belly guard | SOLID Diff cover | Cobra CB radio | 4xG CB radio antenna mount
P0300 is not a good code to troubleshoot on electronically controlled ignitions. More often than not, its an ECU issue when the plugs are fouled like that (otherwise normally a fuel supply issue).
Did you put new plugs in?
Have you changed the PCV valve? That seems like a log of excess blow-by in the intake.
Thanks cricket and Matt for the replies. In addition, I switched around my ASD relay with another relay in hopes that maybe an intermittant relay was causing the interuption in fuel, but it didn't work either.
I hope it's not something that serious. I'd think if it was a bad spring or a bad coil that it would throw a specific cylinder code rather than the general P0300 code, but I'm not sure how the computer actualy identifies a misfire. I can't imagine multiple coils going bad at the same time. Although lately I'd believe almost anything.
I did change the plugs but not the PVC valve. I did run out tonight and picked a new PVC valve from O'riely's, I'll swap that out in the morning (I like the cheap fix options).
As far as it being an ECU issue, would that be fixed by reloading the factory tune (I was running the Hypertch tune) and in this whole process have reprogrammed a few times both the factory tune and the Hypertech tune. -OR- would a dealer have to reflash it? Or is it possible that the ECU itself is bad and needs replaced?
Matt, when you say fuel supply issue, are you thinking fuel pump issue? or injector issue?
One other thing I saw somewhere was that carbon buildup on the exhast valves can prevent the valves from seating and sealing completly and create the problem. Compression testing could help identify this issue. You don't happen to know what the cold compression numbers should be on a 3.7 and how much variance between cylinders is within standards do you?
Thanks again for the help.
I would definitely load the stock tune before doing anymore troubleshooting.
Normally ECU issues that result in P0300 result in an new ECU, not just programming.
Fuel supply issues could be anything from pressure bleed-off to the pump going bad. Doubtful that its an injector issue because you have a better chance of getting struck by lighting while you're on your way to collect your mega millions lottery winning than you are to have multiple injectors go bad at the same time to cause P0300.
I'm not sure what the compression numbers are off the top of my head.... but that engine would have had to been neglected for a long time for carbon buildup on the valves to do this. Again, it would have to be multiple valves at the same time to foul all those plugs.
How's your oil level?
Oil level is good.
I just wish the odds of winning the Mega Millions jackpot were more like the odds of my Jeep throwing a P0300 code on the way to pick up a 12 pack.
I was afraid of that.
I just might have to invest in that service manual afterall.
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