996 3.6 misfiring

[5STM5]

On a run yesterday and had to head home early. I was sitting around 3k rpm and 55 mph when I felt something rough, there were no warning lights so I thought I may have driven over something. A short time later it happened again, this time with an Engine Warning alarm and the car was running really roughly.
I pulled over and switched the engine off, restarted it with no warning lights but when I accelerated the misfiring started again with a warning alarm. One thing I noticed was the Oil Pressure gauge fluctuated slightly when it was misfiring, it’s usually very steady.
I nursed the car home around 15 Miles.
Could this be a fuel grade problem, or spark plugs? Or can I be looking at something a bit more serious? I had the water pump replaced recently, is there anything in that area that could have been disturbed?

[rival38]

No expert, but I doubt it is fuel. If you are lucky it could be a spark plug or coil on the way out. But there are other possibilities like a varioram fault which i think can cause sticking lifters. I would talk to a local specialist and get it hooked up to a diagnostic reader as soon as possible. IIRC there was a renlist thread a few years ago and a misfire was eventually traced to a failing AOS after the OP had spent a few bucks replacing things pointlessly. Would a failed / blocked CAT cause a misfire? I think it might, probably unlikely as they dont fail much. A trip to the garage is probably innevitable, but hopefuly nothing catastrophic to be discovered.

[EGTE]

Sounds like coil pack(s).

[5STM5]

I've just driven it up and down my driveway, definitely still misfiring but no alarms now. Fingers crossed its something simple like plugs or coil packs.

[Chris Stott]

MAF?

[medieval]

Mine had this and as mentioned above it was down to failed coil packs and a lead in my case
Regards

[nebpor]

Chris Stott said:

MAF?

Won't cause a misfire, normally just leads to heavier than normal fuel usage and down on power a bit.

I think my oil filler pipe has a leak, as I was buggering about in the engine bay yesterday and the car feels cleaner and quicker today!

[5STM5]

Surprisingly fault codes showed 3 cylinders misfiring, 2-4-6. Going for the plugs and coil packs first, all 6, hopefully that will sort it.

[5STM5]

As suggested the coil packs were the problem. Car is running great again.