Hi everybody - well, I’ve Googled the subject, so I know I’m not the only one with the problem. I have a 2004 PT Cruiser with 111,000 miles on it. A summer or two ago, whenever it got hot out, the check engine light would start to come on. Usually, it didn’t affect the car’s driveability - but sometimes, it would cause the car to buck and/or stall, sometimes to the point of stalling completely out. Brought it into the shop again and again. Cam shaft sensor. O2 sensor. Crank shaft sensor. Replaced. Checked. P0304 misfire code came up in diagnostics again and again. Re-wiring of camshaft sensor wires. And on and on. And yet again, intermittently, the check engine light would come back on and the whole thing would start all over again. Sometimes you’d drive it, stop somewhere, start it again, and the check engine light would be gone. Sometimes it would stay on for days. Weeks. Sometimes with no other driving symptoms - it just depends on how the car is feeling? I thought the problem was limited to the hot months of summer, but now it’s the dead of January in Minnesota and it’s happening again. Yesterday, it stalled out completely and I had to get it towed to the shop - decided to try a new shop, they said maybe the problem was that the old shop did a bad wiring job. OK. But then, got the car back, no check engine light on first drive, stopped somewhere for 5 minutes, get back in, start it again, check engine light back on. But at least the car started and didn’t buck/stall. Now it’s back in the shop, but I’m ready to give up. Any help?
Is the P0304 misfire code the only one that comes up, or have there been others?
I believe that’s the only misfire code that’s come up, through all of this. Thanks.
A P0304 is a misfire that is very specific to only one cylinder (the 4th). I have no idea why anyone is looking at O2 sensors, or cam and crank sensors and all of that. Those things will not produce a consistent misfire code that is confined to only one cylinder. For one thing they do have their own kinds of error codes. For another, if there was some system problem with these items resulting in misfires you’d get more than one misfire code.
Anyway…how old are the plugs and wires? The “norm” for any misfire code is to replace plugs and wires if they are anywhere near due. The reason is that these things often do cause the problem - and they don’t cost very much and are NORMAL maintenance items anyway. So nothing lost if the misfire isn’t solved.
After plugs and wires, my own preference is to go straight to checking the compression. There’s no point in chasing one’s own tail if there’s a mechanical issues. After that I’d test the ignition coil and swap the fuel injector from the offending cylinder to another and see if the misfire follows the injector.
Anyway…perhaps there is more info from what shops have done that would make sense out of why a P0304 has been dealt with the way it has.
Plugs were switched out pretty recently. I’ll use your other comments as reference when discussing things with the shop. I appreciate it.
You do know the plugs are supposed to be changed every 30000 unless you have the turbo, right? Also stick with the plugs that came with it.