Changed spark plugs, now getting new misfires

Post by **abscate** » 23 Feb 2019, 03:56

Nice catch Mike

Wiring is also a definite inspection item and would’ve fit the symptom list

catchmeifucan652 · Post by **catchmeifucan652** » 23 Feb 2019, 19:06

I took apart the wiring harness and found a couple of spots with cracked wire insulation, particularly with the hot and common wires cracked near a frayed ground going to cyl 2. Cyl 1 and 2 share a ground circuit. I thought I had it figured out, but nope, not yet. Everything is exactly the same.

Yes, the bad cylinders are getting 12V. I'm not sure if that's a good or bad sign for my ECU. I also checked the fuse on the coil circuit and it seems fine, measuring open circuit. A friend suggested an inline spark plug checker, but at this point I don't know what I would do with positive or negative results. This is mind boggling.

I ordered new coils packs, and if that fails, I'll take it to a good shop. I figure the shop is going to make me buy them anyway, so I might as well buy them at an online price and see what happens.

93SCMax · Post by **93SCMax** » 23 Feb 2019, 19:43

Your issue isn't your coils. If you've moved #1 and #2 to other cylinders and they work fine, then they aren't your issue. Good coils moved to #1 and #2 cause a misfire. Replace them if you like, but your issue is strictly with cylinder #1 and #2, either grounding or a wiring issue or something common with both cylinders. Don't let a shop tell you what parts need to be replaced if the data indicates otherwise.

A common ground point for both cylinders, or broken wiring would be the next place to look.

Post by **RickHaleParker** » 24 Feb 2019, 00:17

No misfire before changing plugs. Misfire after changing plugs. Have you considered it might be the new plugs. Try reinstalling the old plugs and see if the misfires go away.

Post by **precopster** » 24 Feb 2019, 04:27

I'm quite sure you meant the fuse was measuring closed cicuit. Besides a blown fuse would take out all 5 cylinders.

As above or swapping plugs from "good" location to misfire location if they're already in the trash.

Post by **abscate** » 24 Feb 2019, 05:51

Upthread, the OP replaced new plug so with old working plugs, and misfire remained.

This one is going to be interesting.

Post by **RickHaleParker** » 24 Feb 2019, 06:51

abscate wrote: 24 Feb 2019, 05:51 Upthread, the OP replaced new plug so with old working plugs, and misfire remained.

I missed that, he did reinstall the old plugs on #1 & #2.

Two things misfire on adjacente cylinders is a symptom of are:
1. Blown head gasket between the two cylinders, which is possible but unlikely in this case.
2. Misinterpreting the layout of the wiring harness and getting the two connectors to the coil packs swapped.

Each of the five coil pack have one wire that is a different color then the other coil packs.
Cylinder #1 Blue wire.
Cylinder #2 Brown wire.
Cylinder #3 Red/White wire.
Cylinder #4 Pink wire.
Cylinder #5 Violet wire.

93SCMax · Post by **93SCMax** » 24 Feb 2019, 12:21

RickHaleParker wrote: 24 Feb 2019, 06:51
2. Misinterpreting the layout of the wiring harness and getting the two connectors to the coil packs swapped.

Excellent suggestion.

Switching wires by mistake is one reason I only do one cylinder at a time...learned the hard way many years ago.

Post by **abscate** » 24 Feb 2019, 14:46

I fat sharpie mark both coils and connectors on coil on plug cars

Sentry1974 · Post by **Sentry1974** » 25 Feb 2019, 23:28

This post changed my life. Going through a divorce. Bought the car with issues with the intention of trading up from my volkswagon. Previous owner messed up the timing. Turned out it had bent valves. Rebuilt the head. Was running like a pos. Struggled for days researching misfire issues. Found this. Swapped coil wires. Presto. Runs like a dream. Thank you rickhaleparker. I needed the win.