S70 Misfiring

bigrig1523 · Post by **bigrig1523** » 21 Apr 2013, 15:55

Hello, I have a 1999 S70 and the other day driving on the highway I began to lose power and the check engine light began to blink. The same thing happened to me a few years ago and I changed the spark plugs and the problem was solved, not so lucky this time.
After I put in a new set of plugs, I had the codes pulled and originally it came up P0301 (misfire cylinder 1) but recently it's been coming up P0300 (misfire in multiple cylinders). I disconnected each individual coil packs, one at a time, while the engine was running and cylinders 1 and 2 were the only two that had no change on the rough running engine. The coil packs on cylinders 3, 4, and 5 when pulled almost made the engine stall. The other night I pulled the fuel rail and soaked the injectors over night in SeaFoam, reinstalled them the following morning and nothing changed. I'm not sure where to go from here. I think I've isolated the problem to cylinders 1 and 2. The check engine light was on previous to this incident but that was for the O2 sensor. Any help would be greatly appreciated. Thanks, Big Rig

Post by **abscate** » 21 Apr 2013, 16:08

Did you replace coils 1 and 2? You could swap coils 1 and 5, and then 2 and 5 (keeping the coil numbers the originals) to firm the diagnosis. If the 'weak cylinders move with the coil(s), VOILA!!

bigrig1523 · Post by **bigrig1523** » 21 Apr 2013, 16:12

I did, I swapped 1 with 5 and 2 with 5 and the engine again almost stalled when 4 and 5 were pulled and kept running rough when 1 and 2 were pulled. I failed to mention that.

Post by **abscate** » 21 Apr 2013, 19:05

I think that isolates you to either fuel injectors or valves in the affected cylinders.

Post by **E Showell** » 22 Apr 2013, 09:19

How many miles? Do a compression check on the affected cylinders. You may have a valve leak. If so, you face some tough and/or potentially expensive decisions.

bigrig1523 · Post by **bigrig1523** » 22 Apr 2013, 09:28

Thank you. 220000 miles on it. I haven't done a compression check yet but that was going to be my next step. I absolutely love the car but with 220K on it.....

Post by **burnout8488** » 22 Apr 2013, 11:06

Pull the rail and point it upwards with injectors installed. Have someone crank the car. You'll see a light mist from each injector. Whichever one isn't spraying is your problem. If all 5 are fine, you can rule that out.

bigrig1523 · Post by **bigrig1523** » 23 Apr 2013, 13:34

All injectors appear to be firing correctly. I pulled cylinder 1 and 2's spark plug and it looked and smelled like fuel. I think a may have a few bad valves. Thanks for the help.

Post by **E Showell** » 23 Apr 2013, 13:57

Running for prolonged periods with a vacuum leak, valve stem seal leaks, extended oil change intervals, running regular gas in normally aspirated models and failed front O2 sensors may all be possible causes of a burned valve. This has been covered extensively on this Board. Search away.

Post by **rspi** » 23 Apr 2013, 18:08

I have 225,000 and my compression numbers are 175+ across the board. Like a car with 50,000 miles on it. These motors are designed to last 500,000. Timely oil changes and good oil filters are the key. My PO changed oil all the time but didn't use proper oil filters and now my valve stem seals are bad.