HELP! Misfire
 

I got a 01 volvo s40, it's getting a misfire code for cylinders 2&3. So far I checked fuel pressure which is at 40 psi, I swap the injectors with cyl.1 and 4 cyl. same with the coils and plug wires, compression is at 143psi both cylinders, I did a block test and checked plugs for antifreeze signs, has new plugs. I have reset the codes 10 times and it's 2 and 3 cyl everytime. It would be highly unlikely a sensor would target just 2 cylinders, vacum or turbo problem 2 for that matter. I'm taking the cam cover off right now to inspect the the valves and cam lobs. I really doubt there's going to be an issue there seeing that there is no funny valve noise. Anyone got any ideas? This car has got me banging my head against a wall. Someone told me this car has got oil driven valves that can plug up, are they cylinder spacific?

I should mention to the live data is showing its not running lean or rich while driving or freeze framed codes, everthing looks as it should, at least as far as I know.

It does have a camshaft re-set valve that feeds oil into the exhaust pulley hub - do not think it would trigger a mis-fire. I would suspect the coils and wires - possibly connectors my self

Coils is my guess. They don't call for a replacement of these at any specific interval but they seem to go somewhere around 150k miles.

Thanks for the replys, I switched the coils and wires from the 2 3 cylinders to 1 4 and made no difference, it still had the 2 3 misfire

how do the connectors to the coils look? they've been known to crack.

They look ok, don't appear to be damage but I was wondering if it could be the wire or connectors. I looked them over and just don't see it could be them. When I pulled the dipstick I seen just barley a milky swirl in it. I drained the oil and don't see any evidence of antifreeze. I been sick so havnt been out there but going to get that cover off and see if there is any milky stuff underneath. Thing passes a block test though, compression is good, do you guys think it's still possible head gasket?

not sure how to conclude you have a head gasket issue without a few more bits of info - are you consuming coolant? did you do an HC test for the coolant? are you consuming oil? A bit of foam on the dipstick could simply be condensation that hasn't had a change to boil off. If none of these are happening, I'd go back to the things in play with the ignition - are the plugs the right temperature range or set to the correct gap (don't assume out of the box they are correct to .030)? how many miles on the coil packs? is it time to try and replace one or both? did you try running the engine with the wire cover off in a dark garage to look for any arcs? (water mist may help)? How about the age of the wires? Lastly, did you consider the knock sensor? I'm with Pierre in thinking coils or connections to/from the coils so it may be time to leap of faith replace 'em.

you could try one more thing: this topic seems to be controversial but I've read several threads where switching back to Volvo plugs addressed misfire issues. I know, I know, a properly gapped premium plug should be no different but take it as you will. Apparently this particular volvo is quite particular about its plugs. New coil packs are not cheap...I hate to suggest this but it might be time for a pro's opinion ie dealership. One hour billed to you might save you down the line.

Good point, my 2000 S40 is very happy running with the copper core Bosch 7955 FR7DC's - now on sale at FCP for $1.49 per plug so for $10 you can experiment :-)

Have you got to the base of the problem? got the same problem except mine is no1&2 cylinder - fitted new coils new plugs problem still there, pulled the fuel rail all injectors pulsing, got 11bar on compression check - feel like taking a box of matches and light it up :mad: - cylinder head has been reconditioned, new head gasket the works

Hahahahahahaha, problem solved, the engine was stripped when I bought it being a Volvo virgin I had the freakin plug wires the wrong way around 1 to 3 and 2 to 4 - where it should be 1 to 4 and 2 to 3 - thank you google images :D:D - so relieved as this was driving me nuts and angry at myself for being stupid

Sorry for my late response, problem solved. Tiny little crack in the wire that goes to the coil has been causing all the problems (see attached pic). It seemed like a ignition issue from the beginning but this car had so many dam problems. While inspecting I found my fuel pressure regulator was also leaking fuel into the vacum line and my turbo sensor had a code (replaced)when I first got the car. As I said above the car does pass a block test & compression test. I think who ever said (the milky on the dip stick it's just condensation) is right and I feel the head gasket is good to go. While I got it apart I'm going to do the timing belt. I appreciate the replys.