2004 Volvo S60 2.5t stumbling, valve rattle and power loss

[CoolWolf22]

Hello all. I do apologize if this exists elsewhere in the forums. I did try to search for something similar, but have not yielded any results as of yet. Anyway, on to my problem(s).

I bought my 2004 S60 2.5T FWD within the last 4 months. Has been running strong. I've put on approximately 5,000 miles since purchase. I've stuck true to my preferred service intervals of 3,500 miles per oil change. The car is running Castrol Semi-syn 5W-30.

The problem started yesterday when I went out for a 85 mile drive. I always fill up with 91+ octane fuel when ever she needs more fuel. When I was on my way home, I noticed that I had power loss and it felt like she was stumbling over herself at and above 3k RPM. I had the a/c on and the radio cranked so I didn't notice the engine noise at first. So after feeling the issues, I pulled over and turned the a/c off, the radio off, and rolled down the windows. Seemed like she was running fine until I gassed on her and got her above 3k RPM. That's when I not only felt the hesitation, power loss and stumbling. But also heard the valves rattling something fierce. The problem doesn't seem to persist below 3k RPM and seems fine at idle.

I finished driving her home, being easy on her, and parked her to let her cool off so I could check the spark plugs. This morning, 8/11/2014, I pulled all 5 plugs and noticed that cylinders 1, 3, and 5 were all uniform black carbon build up while cylinder 2 was black carbon build up with wet residue and cylinder 4 was relatively free from carbon build up. I cleaned all 5 plugs and re-installed them. Started her up and she stumbled at first, but smoothed right out. I let her idle down to normal engine RPM before putting her into gear and taking off for a test drive. She ran hard and strong all throughout the RPM range. That is until she was at normal engine temp. That's when the problems mentioned above came back.

I'm at a loss as to what's going on with her. She's not throwing any CEL's or codes in the information center. I've only ever ran premium 91 octane or higher in her since I bought her. I've tried checking around on the internet for similar issues, but as I said I haven't been able to find anything remotely similar in nature.

My 2004 Volvo S60 2.5T has approximately 87,000 miles on her. Fresh oil, moderately cleaned spark plugs, reset the gap to .028, and is FWD. I do hope that someone here can help me resolve these problems. I'm leaning towards her either needing a new fuel filter or possibly new coils. Not sure what else it could be.

[chrism]

I would first try the quick and free stuff, like check over all of the intake air plumbing and make sure it's all connected up good and tight.

[vtl]

Yeah, check the plumbing. Otherwise find somebody with DiCE/VIDA setup and read the codes.

[draser]

What I'm reading is that car runs ok up until warms up. It sounds like the engine continues to run rich after warm up, which jives with your black and soothy plugs.

[regent]

Running rich when warm may be a good indication of a faulty ECT sensor signal.

[CoolWolf22]

What I'm reading is that car runs ok up until warms up. It sounds like the engine continues to run rich after warm up, which jives with your black and soothy plugs.

It just started doing this the day before posting. Never had any issues with it prior.

[CoolWolf22]

Running rich when warm may be a good indication of a faulty ECT sensor signal.

I'll be sure to check that out the next time I get a chance.