2004 XC90 T5 rough idle CEL, MVSOLVED. Bad coil

francisp · Post by **francisp** » 07 Jul 2014, 19:50

Sudden rough idling and eventual CEL coming on. XC90 T5 AWD with 162,500 miles. Just had oil changed in the last 24 hours, air filter replaced, shot some seafoam into tank and filled w/ 93 octane. Been very gentle with it since I got it 3 or so days ago. Even put new tires on it. Now I'm just stumped and worried it could be a major repair. Some thoughts and insight would be appreciated. Many Thanks!

Stravlr · Post by **Stravlr** » 09 Jul 2014, 14:21

Best guess - you have a Vacuum leak, look at/near all the thing you touched for the small hoses and make sure they re all in place.

Other than that - get you codes scanned and report back.

francisp · Post by **francisp** » 09 Jul 2014, 17:04

As per my friend Stew suggested, I got the code read and it said Code P0302, cylinder #2 misfire, so off I went to meet up with him and we removed the coil pack from cylinder 2 and the boot that fits right below the ignition coil was the culprit. It had a tear in it which may have caused it to idle roughly. Everything is running smoothly once again and the CEL has been shut off.

Stravlr · Post by **Stravlr** » 09 Jul 2014, 18:51

Great! I don't know about you but, I love an easy fix!

Post by **cn90** » 10 Jul 2014, 10:27

If you have not replaced the spark plugs, time to consider Iridium plugs.
I did mine as below:

https://www.matthewsvolvosite.com/forums ... 10&t=64080

atomic_80 · Post by **atomic_80** » 15 Jul 2014, 12:51

My 2005 XC90 2.5T was doing the same thing. I pulled off the coils from a '99 S70 to get me through a trip and it did alright. I ordered some used ones from Tom's Foreign Auto Parts and they have been ok. I have the platinum plugs install but I still get a slight surging when idle. No variation seen in the RPM but sort of a rev up/down feeling. Any thoughts on what is driving that?

francisp · Post by **francisp** » 03 Aug 2014, 09:59

Just to followup on your slight irregular revving, the problem I had with mine was a torn rubber boot. I'd check then individually just to make sure they are uncompromised.