ballajb

I have a 1991 H.O motor with aluminum heads, longtube headers, F303 cam, typhoon upper and lower intake, and msd (dizzy,coil,6AL box) and 5speed transmission. For some reason i can not go past 3500 rpms, what could be the cause of this and what can I do to fix this problem?

mattdel

anything done to the motor prior to the problem?
MSD dizzys are notorious for having crappy ignition pickups(PIP), so you might try to test/replace that as a starting area. It's definitely an ignition/fuel problem.

RICEBORDEAUX

My car was acting like this once and it was the MAP sensor..I read it with a scanner and the problem was fixed after I installed the new map sensor, just my two cents...

lxman1

91 is MAF not MAP. Could either be clogged exhaust (cats), weak valve springs, lack of fuel, weak pump or clogged filter or bad pick-up as mentioned.

ballajb

i ran the codes while the car was running and these codes came up: 21,42,92,33

mattdel

21: ECT(engine coolant temp) out of self test range. probably bad sensor.

42: Right side O2 sensor not switching. probably dead.

92: O2 left side showing system rich. Could be caused by dead right sensor, but more probable that the bad ECT is causing a rich condition.

33: EGR valve opening not detected. Could be the sensor on the valve, could be the valve, could be you didn't snap the throttle like you were supposed to, during the test.

None of these would cause the symptom you described in the original post.

ballajb

ok so now i replaced my fuel regulator with a holley adjustable one. The problem is still happening. I ran the codes with the car running and the codes that came up are 94, 44, and 33. Now i am starting to wonder if it could be my msd box. I have a MSD 6AL which has a rev limiter... So im wondering if i need to take that to get tested.

Bubba 95SN

MSD site has testing proceedures. The 7AL-3 acted funny in my friends dragster went to the site got easy instructions. bubba