I have owned an S80 for years and just picked up a 2004 XC90 AWD T6. While driving it home of course the Check Engine light came on. It happened when filling the car with gas to get home. I scanned the codes and it was P0300, P0303 & P0305 for misfires. I changed all the plugs and no dice, same codes. I have now changed all the coils and guess what....the lights on again with the same codes. Here's the weird part...after I clear the codes the car can go multiple starts with no issues and then without warning the check engine light comes on. Any advise will be well appreciated, thanks in advance.

 

I'll throw out some ideas in no particular order...

Camshaft sensor, worn out battery, ECM, EGR valve, catalytic converter?

 

Battery is good, CAT seems to be fine. I will check the others. Again the strange thing is it's on random starts, no consistency except the cylinders. Going to clean the MAF and trace the ground wires as well.

 

A few other ideas hit me.

Proper octane fuel?
Possibly got some bad gas?
Fuel injectors dirty/worn out?
Good cylinder compression?

Could always try some SeaFoam or DryGas and run it. Might help, might not.

 

Last week I started with a 303 error and I replaced the plugs and decided to swap the coils to see it the misfire would jump over to cylinder 4 from 3 (S40 BTW) I ended up with two more error codes so in all I had 303,351, and 352. I then swapped my coils back to their original place. No error codes whatsoever

It did have Denso double platinum in it and I put NGK GP which are a single platinum but is running well.

If you have your old coils still, I would give it a try with them again.

 

I forgot about plugs...it seems XC90s can be plug finicky sometimes. If you didn't go with OEM I would try that. They're dumb expensive but might be worth it if they clear those codes.

 

I just put that in as an afterthought, I have no errors. I do not think the Denso DP were original, had I known I would have replaced with DP. The owners manual states Champion that are no longer made so I did a lot of reading, even called NGK and decided on those plugs, seems to be running great but maybe a call to Volvo should have been done.

Thanks

 

I did this when I replaced my plugs. For my 2005 XC90 2.5T it was part number 8642661.

Here is the IPD linky...
Volvo Spark Plug Set GENUINE VOLVO 113579 8642661

I'm not the "OEM or else" guy. But for the plugs I went with OEM. They've worked great so far.

 

Just throwing this out there as well...

I have had Swedish auto repair places say never put Bosch in BUT I think that is more for the ones with multiple electrodes. Also Volvo dealerships say never put in NGK's and multiple dealerships have said that Bosch makes Volvo plugs. I think if you use single electrode DP by Bosch, NGK, you will be okay, seems the multi electrode should be avoided.

 

Do you guys think all of this might also apply to a 2010 XC60? At 88,000 my check engine light just came on and I'm trying to figure what's up.

Thanks

 

Best to scan and see what codes come back otherwise everyone's ideas are shooting in the dark.

 

+1 on this.

Any AutoZone, O'Reily, Murrays, Advance Auto, etc can scan for basic OBDII codes. Or you can buy your own scanner for under $50. I did just because I got tired of making trips to the auto store. They also got more finicky about turning codes off. With my own reader I can turn off the light, see if it comes back, replace something, see if that fixes it, etc.

If you want more specific Volvo diagnostic info you need to take it to a dealer or shop that has the VADIS system. I think you can somehow get that yourself but it might be pricey.

 

Thanks guys. I'll bring it to my mechanic to let him check the codes for me.