Rough running only at part throttle.

[metaman]

I have owned this car for 8 years and 125k miles. This is the first time that it has done this. The strange thing is that when it first started it was intermittent. It would do it for a few days, then suddenly it would be gone for a day or two.

At part throttle only (runs fine under boost), at around 2k rpm the engine runs rough enough to rattle the ac vents over the radio until it gets to about 2300 rpm and then it smooths out. More annoying than a serious problem.

I have already replaced the plugs (tr6ix). Cleaned the mass air sensor. I am thinking that this may be a sensor loosing resolution until the rpms come up. Could be the mass air, or the 02.

The other thing that it could be is a vacuum leak. The only place I can not check is the pcv line under the lower intake. If that one is leaking, it would explain why the car is fine under boost also.

 

[hotcobra03]

if no engine light...my first thought was coils are getting weak..

i had a problem and it took awhile to find it..

my started like that and got hard to drive...we drive easy..if you pushed it and stayed above 2500prms car felt fine..

i found it almost impossible to drive around slow..car would jerk/miss/sputter...it would come and go...

i would do a compression test..and find a local member that might have a set of 8 coils to try..this will help you to decide where to look and its free

it could be alot of things..im assuming you already cleaned air filter/maf/tb inlet..and checked for vaccum leaks