1997 850 intermittent CEL - misfire code

thedancingfiddle · Post by **thedancingfiddle** » 28 May 2015, 17:11

Hey all,

The check engine light in my 1997 850 recently started coming on, and then it will go off after a couple days. This has happened four times now in the last few weeks. Finally I got a chance to read the codes, and there was one code: P0304 - cylinder 4 misfire.

The car seems to run totally smoothly, and has plenty of power. I have noticed that the last couple times the CEL has come on, it was when I was sitting in traffic, so the car had been idling/lots of slow driving.

I'm assuming the light goes off because the problem hasn't happened again, right? Does anyone have an idea of why this would happen only after idling a while?

The cap and rotor and plugs are new a few months ago.

Thanks for any and all ideas!

Post by **jreed** » 29 May 2015, 05:00

Some people have reported problems with misfires when they use non-OEM ignition components (especially the Bougicord wires, but sometimes also the spark plugs). What brand of cap, rotor and spark plugs did you install?

thedancingfiddle · Post by **thedancingfiddle** » 29 May 2015, 08:07

Plugs are OEM Volvo, cap and rotor are Bosch....

I didn't replace the wires, but maybe that's the next step. I just wonder about the fact that it happens when the car's been running at idle for a while.

Post by **jgc470** » 29 May 2015, 09:27

I had a similar problem with my 96 850 (180,000 miles). Check engine light on, then off; Code read misfire in #3. Since I had recently completed a tuneup, I felt the problem was with my injectors. I needed to do PCV work, so at that time, I pulled the injectors, and sent them to Marren Fuel Injection in Conn'. The cost ran $25 an injector, they test them before work on them, turn around time was 8 days. They reported poor spray pattern in three of them, but after cleaning, all were within spec's.
My 850 runs much better, gas mileage better, and after driving over 2k miles since work, no codes.

thedancingfiddle · Post by **thedancingfiddle** » 30 May 2015, 07:16

That's good to know. I did recently (a month ago or so) use a bottle of Lucas Injector cleaner. This was before the CEL started coming on often, but who knows....

thedancingfiddle · Post by **thedancingfiddle** » 31 May 2015, 20:11

Any other ideas?
The CEL went off again last week and hasn't yet returned - I put on over 500 miles this weekend, and not all highway driving. I'd like to have more input before I talk to my volvo mechanic - taking out the injectors myself is more than I want to get into right now, especially since I need the car on almost a daily basis. Seems to be getting plenty good gas milage on the highway also...

Post by **abscate** » 01 Jun 2015, 04:37

How does the spark plug look on that cylinder? If it's the same as the others then move it to a new cylinder and keep driving it. See if the cylinder misfire moves. Keep track of the plug locations.

You can have a bad, brand new spark plug.

Post by **shaker_chi** » 01 Jun 2015, 16:16

I had the same issue and at first glance I didn't see anything wrong. Once I pulled the boot off the plug I noticed it had some corrosion on it and wasn't in the best of shape. With that, make sure you pull the wire off that cylinder and give it a thorough inspection. With OEM plugs and bosch parts you should be ok on that end. Good luck.

Post by **jgc470** » 02 Jun 2015, 11:46

I agree with above post, check plug and wire first, the removal and cleaning of injectors last. I would add that there is a couple of excellent post in the forum to aid the injector job. As I mentioned I did cleaning job as part of PCV work, and those post helped with fuel rail/injectors work. Good luck.

Craigd2599 · Post by **Craigd2599** » 05 Jun 2019, 04:37

Run the car at night in total darkness. Look for a stray arc from the spark plug boots. Had the same issue with one of my 850's. It was a bad boot that had a small crack that would open up when it got hot and arc against the head.