1988 rx7 t2 street ported when ever I hit 4k rpm the car backfires and doesn't want to rev past 4k like a rev limiter in all gears what can this be? Please help

 

If it slowly goes through 4k when you baby the throttle but falls on its face when you punch it then you have a secondary injector issue which could be caused by poor engine/ECU grounding, clogged injectors, injector wiring which is faulty or the engine is not seeing load.

 

I checked the plug for the secondaries it has good 12 v and ground on both of them I red did the engine grounds where should I start

 

I have 850 secondaries and a fcd

 

1. And you have a stock ECU? If so, then you won't have a way of controlling the larger than normal secondaries thus you might be pushing too much fuel.

2. And you didn't respond to the query of whether you could baby the engine through the 4K level.

3. Also, you can measure the voltage on the ECU injector trigger wires to see if they are reading the correct voltage as they should go from 12 volts to 6 volts when you hit close to 3800 rpm.

4.The injectors wires at the ECU should all measure 12 volts w/key to on. Do yours?

5. And you have a turbo boost sensor and AFM?

6. Lastly, has this always been a problem or not?