Last weekend my wife and I had met to pick Halloween stuff for the kids and were almost home on some surprisingly empty streets. She pulled up next to me a gave her Mini a few quick revs to which I responded with a few of my own from our kid-getter, a 2001 V70 T5 with 149k. The light turned green and we took off. The turbo launched the old wagon way out in front and I accelerated full on all the way up to the 40mph speed limit and then let it coast while my wife caught up at the next light. Now the Volvo was running really rough – like maybe it wasn’t running on all 5. (I got the same exact feeling in my BMW 318 last year when the oil cap came off after a quickie-shop oil change - once replaced vacuum was restored and all was well). I was hoping for some easily visible problem like that in this case, but not to be. I had just replaced the upper engine mount that morning so I was hoping that maybe it was something to do with the turbo hose which I had to push aside to get to a bolt. There is no air escaping at either end of the turbo hose that I can tell. My wife says the car smells slightly of something burning, although not surprisingly I can’t smell it. There are no knocks or any other strange noises. The oil and coolant look no different than before. I tried driving it last night to see if there was anything else I could tell. The check engine light is now on constantly and actually flashes when you hit the gas hard. So I’m not sure what to do. Any ideas?

 

Check your coils to see if they are all firing. Make sure spark plugs are not fouled. If you don't have an OBDII reader stop by Autozone and have them pull the codes.

 

Great - I'll check those items out. Thanks!

 

If you get a misfire code, say on #2. Swap the coils like #2 with #4 and see if the problem follows.

You should get a code reader if you plan to do your own work.

 

Pulled the coil wires one by one and found #3 was dead. No apparent plug fouling. Replaced it with a generic from Pepboys and we're back in business except for the Check Engine light which will not go out. Can't imagine that the couple of miles it was driven home with a dead coil trashed the emissions system, but you never know. Thanks for all the advice - still need to aquire that code reader!!

 

It might have fouled up an O2 sensor, you usually have to really overdo it for that to happen though. The codes wont clear immediately, but it should be gone after three successful cold start cycles. So if the CEL is still on after that, get the codes pulled and go from there.

Code reader wise, IMO the best way to go is an old laptop as you can do a lot more with the OBD data. I use a Toughbook CF-27 for OBD diags, you'd probably get one for under $100 now. Its been out in the garage for three winters now and the battery still holds a charge LOL.

/edit: Heres one for $70 its a touchscreen which is handy to have too: http://cgi.ebay.com/PANASONIC-TOUGHB...ht_3952wt_1139

 

You nailed it - the CEL was gone when I started it up on Monday am! I ordered another coil from ebay just to have on hand when the next one goes. I freind said his coils started going one after the other around 150k. Unfortunately he was off the the stealer each time to the tune of several hundred beans a pop.