1991 740 engine misfire and rev counter erratic

[volvobusman]

Hello again, today I have had a look at my father in laws car, replaced the ht leads, tried his amplifier module on my 940 and it ran perfect, checked for vacuum leaks and replaced various pipes with new pipes, tried the MAF sensor, the car has new spark plugs but not to say one is faulty , I have noticed that the car rev counter has stopped flickering but did start again, I have checked the rpm sensor on the bell housing, not sure what the resistance reading should be, mine was 167 ohms and it was 203 ohms on the suspect car, asked if it runs better when cold as if there may be something breaking down when hot, also if the car is revved very slowly it runs perfectly but if you accelerate as normal it misfires almost like a flat spot, going to do more homework on this but any help would be gratefully received, cheers Andy.

[bob12]

Maybe the coil? .... I wanted to send just 'coil?' but the system doesn't like that!!! I have the resistance readings somewhere if no one else provides them.

[volvobusman]

Hi there, tried the coil on my car, it ran okay, just started the car from cold, rev counter okay but still a misfire when revving the engine but smooth as can be when revved gently , cheers Andy

[bob12]

OK .... still in basic mode ... have you opened up the distributor cap and replaced it and/or the rotor ... any engine oil inside? Of course, if it's a B200F you can check the fault codes without any addition gear.

[volvobusman]

Had a look in the dizzy, a bit dirty but nothing bad, cleaned it out, was going to swap the cap off my 940 to try it but ran out of time , checked the codes all 1-1-1, be next week again before I can look at it again, car being used , any other thoughts on this problem ?, cheers Andy