can any one help? if i take of my oil cap when the engine is running the car starts misfiring but if i put the cap back on and turn off the engine and start it again its ok??????? i tried this on cov_robs car and his was ok. any ideas???

You could be allowing too much "unmetered" air into the system

how can i sort that out then mate any ideas?

any one got any ideas yet?????

tell us more about the misfire... is it a random misfire or a consistent, rythmic cylinder drop misfire? does the rpm drop when you remove the cap, if so, from what, to what? have you ever replaced or cleaned the pcv valves?

i hav not had the car long mate i dont know what the pcv valves are? But the car miss fires on all cylinders i think. The revs dont drop at all but as soon as i put the cap back on and turn off the engine and restart it its ok. It runs sound apart from its a bit taperty and it needs a good service. It boost well a drives well so i am confused. Am help will be great.

Sounds like your getting a vuacuum build and when you take the oil cap off it releases it. Pcv valves( postitive crank ventilation) may be blocked, sounds like its air related. JeffTT might give you a better idea, he deals with this sort of thing day in day out.

Leave the cap on :) Why are you taking it off with the motor running ??

i know mate it sound silly but when i brought the car i just had a look at the cap make sure it did not hav any cream in it and then thats how i noticed it and i have neva had it b4 on any car so i thought i would ask.