All,

I'm chasing a stubborn misfire issue on a 98 S70. Actually it is a multiple misfire according to the error codes. Weird thing is it only happens when you accelerate hard, you don't feel it misfiring, and it only pops the check engine light. Driving mildly there is no problem, but get on it and bam ...check engine light. When you scan it is always a multiple cylinder misfire but different cylinders misfiring each time. Compression is fine across all cylinders, the plugs, wires, and injectors were changed but it still has the issue. I'm leaning towards the distributor cap, rotor, or coil since they older parts.....any other suggestions?

 

I agree with starting with a stage 0 tune up - wires, plugs, rotor, cap. When you do the plugs check for color etc. I'd also check fuel pressure and the fuel pump relay and intake air leaks that could possibly cause a lean condition. Last is to check the ECT sensor.

 

Well It appears it was the cap and rotor causing the issue. I threw a new coil at it first just because the old one was a Bosch original and no change. Puled the cap and rotor and saw a lot of arc tracing on the inside of the cap and the brass on the rotor tip was pitted and rough. Put a new cap and rotor on it and so far so good......

 

I probably need to do that on mine. It seems a little fluttery but I don't have any codes. I think it's well overdue. By the way, I have never seen one of these coils go bad. I have no idea what all that extra stuff on the coil is either.