I got my 87 base with s4 t2 swap running but it wont rev past 4k it cuts out and back fires(almost everytime) when it hits the 3500-4000 range. So if someone can help me here, I have not rewired my 255 fuel pump yet- I dont think thats it- and its running with no exhuast- just a cut off downpipe. I dont have a knock control box or a fuel pump resistor. Thats about it, hopefully you guys can lead me in the right direction- i've been messing with it all afternoon.

I have a video of it runnin if that will help you diagnosis
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I had the EXACT same problem last week. I changed my fuel filter and its running perfect now. Change your fuel filter.

 

Distributor problem.

 

it has a bran new filter

 

distributor problem?

 

oh and my fpr doesnt have a vacuum line?

 

American FC's don't have distributers, so if you don't know, don't post.

Sounds to me like your secondary injectors arent coming online, or you're running insanely rich at 4k.

 

how would they not be working- what should i test?

 

run a search for 3800 hesitation. It is a common problem in FC's caused by bad grounding between the bat/ecu/chassis.

-Marques

 

Secondary fuel injectors are not working properly.


-Ted

 

well ive been messing with it all evening ag ain and i still dont have a clue- any more ideas?