(Weird) P0301 Check Engine Light Issue
Today, 12:27 AM
#1
Three Wheelin'
Thread Starter
(Weird) P0301 Check Engine Light Issue
Okay, so I pulled the car out of the garage to give it a thorough washing today. When I was done, I started it to move it back into the garage and it struggled to idle smoothly, eventually throwing a check engine light. I pulled the car into the garage, turned it off quickly, and took out my OBDII reader which showed one code: P0301 - misfire in the 1st cylinder.
I know the problem could be more serious but my first thought was that it could just be the coil. I replaced the spark plugs relatively recently but can't remember ever changing out the coils. Btw, it's a 2004 C4S Cab with 48,000 miles on it. I went inside pissed, ate some dinner, and then it hit me. The same thing happened a year ago, the last time I gave it a thorough wash. It hasn't gotten much use this year so I've mostly just used a waterless wash and detailer to remove some of the dust it's picked up. Anyway, when it happened last time, I put it back on the battery tender, went inside, again pissed, and researched the issue.
When I went outside the next day, I started it again to start troubleshooting -- no more check engine light. The problem was gone. Gone! Cars don't fix themselves but I could not replicate the issue. It's run smoothly the entire year...until today. It was in for routine maintenance late last fall and the tech didn't find any problems. I even had it out for a 2 hr drive yesterday (~100 miles) without any issues. So, out of morbid curiosity, I just went outside a few minutes ago (about 5hrs after I parked it) and started it again...just to see...because there's no way it could really be the same thing, right? Again, no problem. Smooth idle. I cleared the light, checked it again, restarted it a few times to see if I could do something to cause the light to recur. Nothing. No new code, no light, no rough idle.
Any thoughts on what could be going on? A cracked coil? Could something be getting wet and fouling it up? Seems odd. I'm open to any suggestions.
-Eric
I know the problem could be more serious but my first thought was that it could just be the coil. I replaced the spark plugs relatively recently but can't remember ever changing out the coils. Btw, it's a 2004 C4S Cab with 48,000 miles on it. I went inside pissed, ate some dinner, and then it hit me. The same thing happened a year ago, the last time I gave it a thorough wash. It hasn't gotten much use this year so I've mostly just used a waterless wash and detailer to remove some of the dust it's picked up. Anyway, when it happened last time, I put it back on the battery tender, went inside, again pissed, and researched the issue.
When I went outside the next day, I started it again to start troubleshooting -- no more check engine light. The problem was gone. Gone! Cars don't fix themselves but I could not replicate the issue. It's run smoothly the entire year...until today. It was in for routine maintenance late last fall and the tech didn't find any problems. I even had it out for a 2 hr drive yesterday (~100 miles) without any issues. So, out of morbid curiosity, I just went outside a few minutes ago (about 5hrs after I parked it) and started it again...just to see...because there's no way it could really be the same thing, right? Again, no problem. Smooth idle. I cleared the light, checked it again, restarted it a few times to see if I could do something to cause the light to recur. Nothing. No new code, no light, no rough idle.
Any thoughts on what could be going on? A cracked coil? Could something be getting wet and fouling it up? Seems odd. I'm open to any suggestions.
-Eric
Today, 01:12 AM
#2
Most likely a cracked ignition coil. If your coils are as old as the car (original), then it’d be wise to change them all out at your earliest convenience.
I had a similar issue, a temporary P0304 with noticeable vibration that stopped after I restarted my car, the morning after I drove in the rain. I drove in the rain some more afterwards, but didn’t notice any issues. I replaced all my coils about 6 months later to find that they were all cracked.
I had a similar issue, a temporary P0304 with noticeable vibration that stopped after I restarted my car, the morning after I drove in the rain. I drove in the rain some more afterwards, but didn’t notice any issues. I replaced all my coils about 6 months later to find that they were all cracked.
