My car had a problem where it'd randomly misfire. Checking the codes it was cylinder 6 and so I first tried swapping the ignition coil with another and ruled the coil out. Then I took the spark plug out and tested it with a multi meter and it was the culprit. I changed it and the car ran and runs smooth and the codes were gone. But there's one exception. If it sits overnight or over a weekend and is started up, it misfires for under a minute then smooths out and is fine. The error codes also come back when this happens, still cylinder 6 misfiring and P1320 which I believe also means a misfire. These are the same two codes I was getting before but again they go away after it stops misfiring. As a test, after it was running fine I backed the 6th cylinder's coil out a little just to make sure the engine sounded worse which it did so I'm pretty sure it's not the coil and it's a brand new spark plug I tested prior to screwing it in so it isn't that either. What could be the cause of this? Is something leaking while it sits or something? It's not a huge deal since after it smooths out it's good to go but I'd still like to fix it.

 

Are they the oem coils or some chinese aftermarket ones?

 

Im not the original owner so I can't say for sure but they're OEM or at least 1:1 with OEM upon visual inspection.

 

could have a leaking injector which dumps all the fuel when it sits

 

Check the Coolant to see if it is Low, If you have a recurring cyl Misfire. A few things to be checked would be a Leaking Injector, That does not mean the Injector is bad, But how it seals is leaking... Did you remember what Color the SparkPlug was that you removed from #6. That may indicate which way to further Test. Check Compression on that Cyl and compare it to the others on that same Bank. A tune up didn't fix it, so now you have to Diagnose it.

 

Sorry for the late reply. The spark plug was black from carbon but other than that just looked like an old spark plug. I;m still thinking it's something with the fuel injector, whether it's the injector itself or the seal as you said. I'll investigate. I'm pretty sure the coolant is nearly at the low bar so I'll sort that out.

 

Check the spark plug/hole for fluid.

 

It could be because of the pigtail wires in the harness for cylinder #6 I've had that problem before with one of my 5th Gen's. All I did was replace the pigtail and about 6 inches worth of wiring and it was all good to go. It's a very common problem with 5th Gen's.

 

Sorry to hijack your thread OP, but I'm wondering if the leaking injector mentioned by others in this thread might be causing my problem. If the car sits overnight, it cranks up and starts fine. But if I run it for 20 minutes and then stop, when I re-crank it starts up fine but then stalls out. The only way to get it started is to pump the gas after it cranks, and that keeps it from stalling out and it runs fine. Would this be caused by the leaking injector?