I have a 2000 Volvo S40. It's been running great, but has suddenly began making a jumping or slight jerking motion after driving for about 20 minutes and generally going up small hills. If I decelerate, it will stop, but once I accelerate again, it will begin skipping or jumping motions. I don't feel it's related to tire balancing as it will work well for a short time at the same speed.

 

Last tune up? How old are the coil packs and wires?

 

Thanks for the response.

It's been a while since I've had a full tuneup. Mainly plugs. I believe the coil packs(though I admit I don't know what they are), and wires have never been changed.

 

Are the coil packs square parts which sit on top of the engine? Is the same as an ignition coil? If so, can you tell me how to determine if they are faulty and how to replace? Thanks,

 

I did put in new ignition coils. Very simple process. I didn't change any wires. It still seems to skip, but the skip may have lessened. Do the wires commonly cause that issue too? Thanks,

 

When I had coil packs changed in my Mazda MPV, they changed the spark plugs as well because they said bad coils will ruin the spark plugs.

Good luck.

 

Great, thanks. I'll check the plugs too.

 

Yes the wires commonly go bad as well.

 

First, thanks for the help. I replaced the coils, wires and spark plugs. The problem is still there and seems to be getting worse. The car has a knocking sound when I accelerate. Once I take my foot off the gas, it stops, so I'm not sure if it's the engine, transmission or what.

 

Check engine light on?
If so what are the codes?

 

Thanks for the response. Yes, unfortunately my "check engine" light is always on. I've had it cleared many times and issues remain many aren'tcritical, but the fact is they won't go away.

As for the code, the only code which registered was P1449. Someone gave me the following definition of the code:

"The only reference to P1449 for a Volvo that I have been able to find was in regard to an 850. The code meant "Diagnostic module tank leakage - pump too high". Unfortunately, no more information was given"

 

You would have to have it read by someone with the Volvo software.