random missing/ lunging under certain loads.

[bloodshot-e30]

alrght this is completely random and i have not found a pettern to it yet. but basically (sumtimes) under 3k RPMs if i gas it it stutters for a second then runs good. then around 4200-5000 sumtimes higher i can feel it lunging not REAL bad but i can feel it, and sumtimes after 5k it runs fine..

it doesnt do it all the time its just completely random. im thinking O2 sensor or some sort of vac leak?

[BigD]

Are you sure it's RPM dependent or just anytime you give 'er? If the latter, then it's probably either a vac leak or a fuel problem (fuel pump?)

[bloodshot-e30]

it seems to be RPM related cuz if im off the gas and above 3k and stomp it then it takes off no stutter and as soon as i get to 4200 and starts the really slight lunging thing.. BUT it doesnt always do it...

[surebimmer]

I've had a customer's car that would do this under load and not set a check engine light. Found his spark plug holes filled with oil from a bad valve cover gasket. It would cause it to miss when under load only.

[bloodshot-e30]

I've had a customer's car that would do this under load and not set a check engine light. Found his spark plug holes filled with oil from a bad valve cover gasket. It would cause it to miss when under load only.

New gaskets and no oil in holes

[BigD]

it seems to be RPM related cuz if im off the gas and above 3k and stomp it then it takes off no stutter and as soon as i get to 4200 and starts the really slight lunging thing.. BUT it doesnt always do it...

Do you have a CEL hooked up? Do you get any codes? Maybe it's losing sync, with crank or cam - at the harmonic vibration at that rpm, something semi-loose becomes disconnected.

[bloodshot-e30]

Do you have a CEL hooked up? Do you get any codes? Maybe it's losing sync, with crank or cam - at the harmonic vibration at that rpm, something semi-loose becomes disconnected.

no cel hooked up... it did this VERY random in my red car as well but not to this extent. ill check out some things being loose and see if i cant find something.

it ran rich as hell for a long ass time thats why im thinking o2 but the only other not new sensor would be the cam sensor... sooooo i guess thats a possibilty.