no power

[midnightmark]

my 98 mark viii lsc has been having a problem for a while now that is really bugging me. when the car hit 3000 rpms the motor seems to miss and the car goes no where as is it has no power at all. and also off the line its very sluggish. im also only getting about 16 mpg when i drive 55mph for about half an hour everyday. I have put in a new imrc control box, spark plugs and boots, and a new fuel filter. the reason i baught the car was for the performance and since im not getting any its really bugging me does anyone have any idea what my problem could be? i thought maybe the cats were clogged does this seems like the symptoms.?

 

[98CobraStarLSC]

sounds to me like you are having the problems right around the time when the IMRCs are supposed to be opening. Might be that the IMRC plates and butterfly valves are gummed up. Try running a can or 2 of seafoam through a vacuum line and see if it helps.
What about the fuel filter? have you ever changed it? also its cheap to do a compression test. and its easy too!
What else can you guys think of?

 

[lunchmeat]

Maybe theirs a wire grounding out somewhere?

 

[shiryu0]

is the check engine light on? codes?

 

[midnightmark]

check engine is not on its not giving me any codes either, i changed the fuel filter a little bit ago and checked the fuel pressure which was good. the imrc arent gummed up becuase i can see them opening when i rev the motor in park and i can move them freely with my hand. i was thinking possibly a ground problem as well but i have no idea where the ground wire is located for the imrc box.