My '92 Marquis LS has a part throttle misfire. I tried running some fuel system cleaner through and giving it run down the highway but this didn't make any difference.
The odd thing is if it is cruised at 120 KMH there's no misfire but if I drop back to say 80-90KMH and then accelerate back to 120KMH the misfire starts again. It also misfires in city driving again on part throttle acceleration.
It has new plugs and air filter. Does anyone have any suggestions as to what I should look at next?
Thanks