Hello-

I have a 2000 S40 with 70,000 miles. The car just developed a misfire on cylinder #2 and is throwing a P0302 error code. When I clear the code it comes right back immediately.

The engine runs fine except for a mis every 20-30 seconds, and soetimes it goes for a minute or two without a mis. I would think if it was electrical it would be more of a steady mis.

No other codes are present, and no misfires in the other cylinders.

Thanks,

 

Have you changed plugs lately? Possibly a bad coil.

 

x 1,000,000
You can check the coil for signs of arcing (burn marks, etc)

P0302 = Cylinder 2 misfire

And in the future, my frequently asked questions thread has a lot of valuable information in it, including this info about misfiring.
Here: https://volvoforums.com/forum/volvo-s40-11/frequently-asked-questions-34712/

 

I also have a misfire on cylinder 2 and I changed all spark plugs and coils. Could I change my wife's out maybe that's what it is?

 

Swapping a wife causes other problems. I'd avoid it unless she's really being difficult. ;-)

If swapping coils and plugs didn't fix the misfire (AND it stayed on the same cylinder), chances are that your problem is is an injector, or in the wiring TO the coil. You can swap injectors from the bad cylinder to one of its neighbors and see if the misfire follows the injector (don't forget to reset the code after the swap, of course).

 

the 2000 S40s use one coil for two cylinders so I wouldn't suspect the coil. I'd start by inspecting the plugs, replacing the two wires (particularly if they have an old date code). I suppose you can swap the coils just to see if the problem moves. The other thing that happens on these cars is the wire harness/connectors that power the coils can develop cracks so take the time to inspect that as well. In terms of injectors, they really don't fail all that often. One easy thing to do is run a couple of tanks of brand name premium 93 octane (ie Texaco, Mobil etc that advertise their additives) or throw a can of Techron in the tank to help clean the injectors. Have you noticed longer than usual cold cranking? If so, that may be a sign that your fuel pressure regulator has a torn diaphram and needs to be replaced (which can cause misfires). The quick test is to find the FPR on the right side end of the fuel rail and remove the S shaped vacuum line off the bottom. If fuel drips out, you need a new FPR.