Failed Ignition Coil caused by wire

[PassCruiser]

Hi Guys, I thought I'd share what happened this morning. Very cold here today, so whether this was part of the issue I'm not entirely certain. Anyway, I was less than 5 min out of town then all of the sudden I had loss of power then engine run rough. I stopped, let it idle, running rough so I turned it off then restarted to only have the same. Popped the bonnet checking coil connectors & coils firmly down & nothing. Couldn't see anything of note. So I quickly turned back for home.

Once back in the garage I connect the OBII reader & it showed P0304, which is engine misfire cylinder 4. I removed the coil & checked the plug, all seemed ok. I swapped the coil with cylinder 3 & while the engine ran rough it was smoother. Now fault code P0300 showed, being, random cylinder misfire detected. So I figured coil 4 was perhaps damaged but something else may be at play as other cylinder were misfiring.

I wiggled all the coil connectors then a new code showed up, P0641, which is an incorrect voltage detected in either the ECM (engine control module) or the harness itself is faulty or plugs not securely connected. Seeing the code was new after me giving a wiggle I figured I needed to inspect the harness.

After removing the wiring harness cover the first thing I noticed was one the wires was too long on connector 4 & was crimped over sharply (the pic doesn't show this but the extra length is visible). Looking closely a kink can be seen just where the red/white wire bends left. That was hard pressed back on itself bending 180 degrees. I straightened it & re taped so it was no longer crimped. I will splice a new wire in but I'm waiting for a terminal tool to come through the post along with replacement connectors.

I fitted the no. 4 coil to 1 & now engine fault code P0301 is showing, being misfire cylinder one. It is running a lot smoother but still rough, & no other codes show now either. So it would seem that coil is shot. I'm yet to pick up the new coils later this afternoon (I'll replace all as if one has failed I figure it's not far off before more suffer the same fate).

If I still have issues with the coils installed I'll post an update, otherwise it's all working as it should.


Random Cylinder Misfire Detected

Read more: P0300 Volkswagen Random Cylinder Misfire Detected

[Umai Naa!!]

I wouldn't stress too much about the other code for now.

Replace the coils, clear the codes, test drive, and see how you go.

[PassCruiser]

Thanks Umai Naa!! all good.

[PassCruiser]

Junked the fault coil kept the remaining 3 as spares.

Fitted new coils, reinstalled patched up coil loom in it's protective cover, started up....smooth....cleared previous fault codes, no new ones. Take it for a test drive load it up up a big hill on the way out of town, pulling smoothly no issues. I plugged in the OBII reader when I got home & no fault codes. A

All good, for now.

I do need to replace that wire & will do so when tools & parts arrive, I'll do an update. Hope this helps for anyone else whom comes across such an issue.