Hi everyone. I recently bought a 97 850 non turbo w/ 214k on the clock. When I first drove the car it would miss at idle only when warm. CEL was not on. I did a full tune up with new fluids cap, rotor, wires, plugs and replaced the pcv system. A day later the car is running rough, the CEL comes on with misfires on all cylinders and a Crank position circuit problem. So replaced the Crank Position sensor and it runs good but i will get an occasional hiccup sort of misfire while driving. As near as i can tell engine temp makes little difference, happens only under light load and relatively rare (once or twice every ten minutes of normal town driving) CEL codes are p0300 random misfire and P0302-P0305. I checked for vacuum leaks and couldn't find any. Any ideas as to whats causing these hiccups?

 

I would check the wires again, Make sure they are getting good connection to the plugs. Did you use oem plugs?

 

I used bosh platinum wires and plugs. I was possibly thinking that coil or ecm could be culprits?

 

These are all ignition codes, and you're getting misfire codes on all cyls, so you are correct to suspect the coil.

What's unusual is that it only happens with light engine loading; usually ignition faults get worse with higher engine load. Also the randomness is puzzling...

Are you sure the plugs were gapped correctly?

The cap and rotor you installed; bosch? You didn't get any greasy residue on the inside of the cap, did you?

Another thing to try; unplug the ECU, ck the contacts for any signs of corrosion. Even if you don't see anything, spray w/electrical contact cleaner and re-assemble.

 

I would definitely take a look at that coil. I had one of my coils on my S60R go bad and had the same issue under light throttle. The car was fine if I pushed her.

 

I noticed that the coil wire was a little loose so I tightened it up and cleaned the contacts on the ecm. Drove the car and it continued to miss. The only code on the CEL was P0335 Crank position code that I was seeing before I replaced the sensor.

At this point im thinking that the BWD Crank sensor is no good and i need to go with OEM.

I believe the OEM sensor is made by MTC. Can anyone confirm this?