S80 2.9l P0300 Misfire ?

[Guest Guest_Greg_*]

Hi,

New to this site, I love it... I have a 2000 Volvo S80 2.9L with 91K miles. I keep getting an error code, emmission service required, I run the OBDII and get p0300, then had a volvo shop check it and they got that it was specificaly the 4th and 6th cylinder misfiring. It only shoots the code when the rpm's hit about 2200, I have changed the plugs twice, switched the coils but still shows it on the same two cylinders. I'm currently trying to find a pinched wire or something, not sure though??? Any Ideas are greatly appreciated. I also changed the fuel to Chevron supreem and added techron cleaner, still no luck.

[jbuck]

Not really familar with your engine.

Are your plugs OEM Volvo? I'm assuming they are since you had it in a Volvo shop. Seems like misfiring issues can often be linked to non OEM additions. How long have you had the car?

You put on all new coil packs? That must have been big $$.

I doubt the fuel would cause this. I've used techron successfully myself a few times.

[Guest Guest]

jbuck thanks for the reply, I didn't make the coil pack issue clear, the mechanic switched the coils from cylinders 4 and 6 with two other coils and we still had the same issue. We originaly put bosch platinum 2 plugs in it then the volvo guy (not a dealership) said he liked the copper core bosch plugs instead so i changed them again, same issue. I was starting to think it could be the head gasket but the two misfire cylinders are not next to each other?? Stumped???

[MrWinkey]

Dump those darn Bosch plugs and put the factory plugs back in ...start there...did you have the misfire before the plugs and if so 0300 is a random misfire not a specific one, if it's on #6 it should be 0306 ;)

[Guest Guest]

Mr Winkey thanks for the input, I got the p0300 and the volvo mechanic must have a better scanner because he was the one that told me it was #4 and #6. Good call on the plugs, I'm going to get some new volvo plugs. I just checked the compression and got the following results. I'm not sure which cylinder is which so starting from the left side looking into the engine bay the compression is:

#1 179, #2 180, #3 165, #4 160, #5 180, #6 180

The center two are low, are they number 4 and 6? i guess I should know that, well anyway I'm thinking now that it is an obvious head issue, warped head and bad head gasket?? Any thoughts on this ???

[MrWinkey]

Mr Winkey thanks for the input, I got the p0300 and the volvo mechanic must have a better scanner because he was the one that told me it was #4 and #6.  Good call on the plugs, I'm going to get some new volvo plugs.  I just checked the compression and got the following results.  I'm not sure which cylinder is which so starting from the left side looking into the engine bay the compression is:

#1 179, #2 180, #3 165, #4 160, #5 180, #6 180

The center two are low, are they number 4 and 6?  i guess I should know that, well anyway I'm thinking now that it is an obvious head issue, warped head and bad head gasket??  Any thoughts on this ???

←

Compression looks ok to me...It's not a headgasket issue I'm pretty sure of that If it is, that would be very very rare

[jleilich]

I would check all of your plug wires. I just went through the same thing with my wife's mercedes. Misfireing on a few cylinders. Turned out it needed a few wires.

first figure out which cyliders are 4 and 6 then swap wires if the error code changes to two different cylinders you have you problem. Or jsut buy a new set , which is probably expensive.

[Bay13]

No plug wires on his car.

If the coil packs have been moved and the same cylinder mifire codes show up you have eliminated the coil packs, next is the plugs, once you have Volvo OEM plugs in the car it will either go away or you will be able to eliminate them. Next would be to check the injectors for those cylinders.