Car's missing, please set me in the right direction

[bryan0]

Hi, I have a 99 GT with a mongoose vortech sq kit and the mph powerpipe. Lately, the car has been missing under load. If i were to put it in say 4th gear at 2500rpm and stomp on it, there would be a constant bububububububu almost like making your lips vibrate back and forth, that's the best way i can describe it.

I have the sct xcalibrator and decided to try and datalog it. I'm not to familiar with which paramaters to test. This is what i came up with:

Red = RPM
Pink = MPH
Yellow = Short Term Fuel Trim 1
Green = Short Term Fuel Trim 2

See how it drops off real quick right before the bottom says 119? That's where it was missing like a son of a gun. What could be the problem?

I'll try different paramaters and post a graph, let me know which ones would be useful. Note, I cleaned the maf to the best of my ability already, so I'm assuming this isn't the problem.

 

[blubullett]

Mine was missing and it turned out to be my coil packs. It would rev fine but if i put a load on it it would start missing at 4000 rpm.

 

[bryan0]

Hmmm... Thanks for the advice, I'll have to check into that. Anyone else?

 

[GT_green_GT]

If possible you need to cancel cylinders tell you figure out what cylinder it is. And check that coil out. It does sound like a spark problem. Narrowing it down to one cylinder helps. Now if its a random missfire on any cylinder you have a different problem.

 

[bryan0]

Well I replaced the spark plugs and everything seems okay now. They only had about 5,000 miles on them but they looked pretty blackened and one or two were even a little bent-looking. Thanks for your help guys