I have a single turbo with a power fc and just had the car tuned everything went fine and car was pulling nicely with minimal knock on the Power FC. after 2-3 days of driving with great power the car starts slowly hesitating off and on every couple hundred RPM's under full boost, part throttle under boost and cruising are just fine no problems. So now under boost the power is off and on all the way through the the gears and i'm getting higher reading on the knock sensor then when it was tuned. At first it wasnt going above30-35 now i see 50-65. could this just be a spark plug thing? i do have an MSD ignition also. I dont see any black smoke coming out of the exhaust and car idles perfectly and i checked all vaccume hoses. Dont know what else to do. can plugs really be bad only under boost? Oh and i also turned the boost back down to low boost and it does it under low boost as well, by low i mean around 10-12 psi instead of 15. thanks for any help.

 

More voltage is required to initiate an ignition spark as the pressure in the cylinder goes up (boost). Partially fouled or eroded (sharp edges worn off the electrodes)plugs may bleed off the spark (at the higher required voltage) before it can jump the gap. Therefore I would suspect ignition (spark plugs, wires, etc.).

Usually, the fast voltage ramp rate of an MSD will counteract some of this, but it still could be the problem.

 

ok well i guess i'll go buy some and try that first. thanks

 

that worked thanks everything is fine now