87 firebird 2.8 MP FI, auto. 20 k on rebuilt eng/trans. Started cutting out during heavy accel - ok during light accel. It seemed like secondary ign breaking down. Found coil wire corroded at top of dist cap. new cap, rotor, wires, plugs and thought it should be fixed, but no. Fuel press slightly low at idle (35 psi), so changed fuel pump, strainer, fuel filter and put fresh gas in tank - no help (but what a pain to get that tank out!). noticed heavy black soot at output of converter when dropped exhaust. Can get eng to rev up after cutting out - not starving for fuel. appears to be ign prob - any suggestions/help would be appreciated. Getting tired of spending time and money and getting no results. Thanks.

p,s. also tried new coil - no change

 

Not trying to be smart, but its difficult to try "everything" and not find a problem. Try to think of the things in between what you have overlooked. Also, when you say cutting out, do you mean completely shutting off? Or stuttering?
Check Fuel Pressure. During Idle, your pressure should be around 41 PSI, but there are variations. Now, when car is running, Snap throttle open and you should observe an increase in pressure, by about 5 PSI. You may have a bad fuel pressure regulator. 35 PSI is not acceptable. You should not look at anything else until you have proper fuel pressure.

 

Thanks 91 chevywt. I know that I was exagerating when I said "everything". It just runs like the ignition secondary is breaking down under load. It is kinda like a major studder under heavy accel. It idles fine and will rev up but cuts out and in a few good times kinda randomly under heavy accel. I checked the pickup in dist - resistance was good. The module connections looked a little cruddy being 20 y/o oem, so I changed it - seems maybe some better but definitely still there. Does anyone know if brain box can cause this? Is there a way to have it checked other than swapping for a known good one? I will probably check local junk yard this weekend and see if I can find a used one.
thanks for any advice you can give me.
GJ

 

did you replace timing gears and chain on rebuild? dizzy?

 

It may be it, but still 35 psi of fuel pressure is not good. it will idle, but would probably cause the conditions you are talking about, since you need the extra fuel under load and higher rpms. Do you by chance have any codes? What is your timing set at also?