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Help! Engine misfire under load.

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Old 05-06-2009, 10:26 PM
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Car: 83 Z-28
Engine: 406
Transmission: TH350
Axle/Gears: 3.70
Help! Engine misfire under load.

I'm having an issue of the engine breaking up under a load. Starts and runs fine but if you give it throttle it'll break up like crazy. It's a sbc with a new pro-systems carb, afr heads solid roller cam, 10.4 compression. Plugs didn't change anything and a new cap and rotor didn't help either. It does have an MSD 6al ignition with an HEI though. Any ideas? Probably change the coil next. Help!
Old 05-06-2009, 10:54 PM
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Car: 1988 Trans Am
Engine: 5.0L TPI F Code
Transmission: 5-spd Manual
Re: Help! Engine misfire under load.

Did you change the fuel pump?
I could be that with all the modifications you don't have enough fuel pressure under load.
Old 05-06-2009, 11:23 PM
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Car: 83 Z-28
Engine: 406
Transmission: TH350
Axle/Gears: 3.70
Re: Help! Engine misfire under load.

Originally Posted by LuckyGen3
Did you change the fuel pump?
I could be that with all the modifications you don't have enough fuel pressure under load.
Fuel pressure is 7 psi. and the pump is fairly new. The bowls are set to about 55 percent full. Doesn't seem to be sucking the bowls dry or anything.
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