I have a 98 v70 wagon engine is b5254t 20V 2.43Lthat has a misfire ONLY after a certain amount of driving. For example, on a 15 minute drive it will not happen. If I drive to multiple places, within the course of an hour it will begin. If I allow the car to sit for long enough, the misfire will not be present when I restart.

When the car does not have a misfire, it runs excellent.

When the car has a misifre it is driveble but very noticeable. This usually turns on the Check engine light. The codes have been misfire cyl 5 and another timecyl4.

I checked compression with all plugs out and engine cold: all cylinders were 180-190.

The spark plug wires are dated 05. They all look fine. The rotor and cap also look to be the same age as the wires. The spark plugs look OK but of course they dont look shiny new.

The fuel injectors look like they may have been replaced once. All wire terminals relating to fuel injectors and ignition have been checked and are in good shape and free of corossion.

I put in a can of techron.

**The Ignition Coil looked to be original so I replaced it with a bosch OEM replacement part. This seems to have lessend the misfire greatly but it does still occur (just less severe and so far no CEL )

The fact that the new coil improved the situation leads me to believe that I still have an ignition related problem. The thing is all my parts lok good and I cant understand how 2 year old parts could be this bad.

Any suggestions on what I should look at or replace next? I am thinking spark plugs, and maybe cap.

 

A simple test might be to switch a plug from cyl 1 to cyl 5 and see if the misfire is now in cyl 1. You can do the same with the fuel intectors, but I would do one at a time so you know if it's the plugs or the injectors.

I have the same problem with mine in Cylinder 1 and have never been able to figure out what is causing it. Sometimes it will go months w/o misfiring and then all of a sudden it will run like crap, but I do lose compression on cyl 1 when it is misfiring, and I always have a little lower comression on that cylinder. Shop told me something wrong with the head.

 

Thanks I will check that out. SO far since I have changed the coil it has been getting better and better. I drove 130 miles in one day and it only starting misfirng once. NO CEL. I stopped for 10 mins and it was good the whole rest of the day.I may change the plugs as well as other similar posts have stated that the bad coil seems to ruin the plugs as well. (doesnt make much send to me but?)

What you said abou the prob with the head: its probably somehting like a casting error causes the head to seep sometimes when the motor is warmed up. I like these cars but their problems are far too great to justify owning one. These newer volvos are designed to keep the dealer service busy. I am selling mine whil it runs OK before it needs a turbo or something else.

BTW: I had an 850 turbo which I ruined the motor on because I was not religious about checking the oil. It had the slow leak form the dipstick O-ring. The low oil light only came after it was way too late.

 

I've been driving turbo Volvo's since 1985 and have never had a problem with a turbo. I change the oil within 4,000 miles (close to 3,000 but go over some). I use regular 10W30 oil too. I'm on my 7th Volvo right now, and have three of them currently. I really like the 850's with the high pressure turbo.

 

I hear you... I like them too but when you look at what things have been replaced at what mileage by mnay owners, it seems like they are built to break

One other thing: I changed the oil filler cap gasket. I guess a common wear item on these motors which then leaks lots of oil spray from the cam under the spark plug cover and maybe onto the tops of the plugs. (tech mentioned this me me in an earlier post.) My car leaks about a teaspoon from just running around the block. I think that may have been part of the issue with the misfire.

 

Pressure in the crank case can be caused by the cc vent system clogged. Groton Volvo Parts site has good illustration of the parts.