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can someone help me with the problem? when i accelerate quickly the engine bucks but only before 4000rpm. the tps has been setup correctly all tune up things done. also the engine runs great somedays accelerates quickly and you can feel the 4000rpm torque jump then other days it feels slower and you can hardly feel the 4000rpm torque jump what could this be?

maybe ur VRIS is sticking or your VRIS vacuum solenoids are busted

You are not supposed to feel vris.. I used to but it was just that they were not working good. check to see if they are opening and check for vacuum leaks. That could be the culprit.

Replace fuel filters and try running a bottle of injector cleaner...

Check your rubber air intake tube between the vaf and throttle body for rips.

Possibly when you give it gas, the motor moves enough to make the rip spread enough for rough running. But when not under hard acceleration it does not open the rip enough to run rough.

thanks for the replies. its funny like cause the engine works fine somedays then not other days. i have noticed that when revving the engine with the bonnet up you can see both valves open at the same time i thought one was supposed to open the the other later. i also have a click noise when i first start the car but not everyday this is followed by hesitation and general slower running. i thought it was a ping.