I had a rebuilt supercharger put on to my 3.8 now it has a stuttering problem

**419ryan** · 03-01-2010

I found a guy that was selling rebuilt superchargers for 3.8 GM engines. I have a 2001 3.8 grand prix GTP. The bearings went out in the original supercharger so i decided to just buy a rebuilt supercharger and slap it on instead of rebuilding the original one.

Now that i have the new supercharger on i have alot of hesitation or stuttering when i apply boost in high gears. Also it has the same stuttering problem in low gears if the engine is over 110 degrees. I Used 108a autolite spark plugs when i did the tune up. i have checked the fuel line.

What could it be? i am thinking that since i have more air feeding the engine i need to have more fuel for the combustion. Should i look into a new ECU? could it be that im blowing the spark out with the new amount of boost?

**silverstreak** · 03-01-2010

Is this car still stock? Could be many things. Vacuum leak, missed or broke connections would be what I would check first. Any codes?

**419ryan** · 03-01-2010

its got a k&n cold air intake. new exhaust.

**silverstreak** · 03-01-2010

Getting it scanned would be a big help. Check all the vaccum lines especially the tee under the s/c snout.

**copgtp** · 03-01-2010

a scan would help a lot.

You definitely aren't blowing out your spark. Does the supercharger you bought have any porting done to it? Either way you have one of two problems:

A) bad vac leak caused by improper sealing of the blower to the lower intake manifold. Did you follow the correct torque sequence? torque to spec??? did you connect reconnect the MAP sensor after your install? do you notice any type of "hissing" coming from the blower area???? Especially when you shut the car down?

B) Cylinder misfire caused by a bad sparkplug wire or bad coil pack. Are you running stock plug wires? Take the wires off the coil packs and inspect their condition.