I have searched the existing threads but have found no answers, i have an 89 na that will only go past 6000 rpm at 1/4 of throttle when in any gear/ neutral will go to redline/ when more than 1/4 of throttle open it is like it loses power. like it isnt getting enough fuel. fuel pump pressure is 20 pounds idle and while in neutral will go to 30 pounds i dont know what pressure it has underload. I have cleaned the tank changed the fuel filter cleaned the lines. when the car is first started it will pull to 8k underload but about after 2 minutes of driving it wont. is it the secondary injectors?... please help,

 

check the injectors for sure....check the sock filter on the fuel pump. Or just replace it because you really can't see if it is clogged up.

 

Check for fuel leaks, primarily near the primary rail. Also, don't drive the car in this condition.

 

I had an 89 AFM go bad on me that did exactly that. It stopped sending a signal once the vane started opening far enough and the car would die on me until I took my foot back off the throttle. Replaced it, and found out from the old one that s5 afms fly almost as well as footballs when you put a good spin on them.

 

Fuel pressure seems a little low. I'm at ~30 @ idle, and ~40 PSI @ WOT. But I doubt that low fuel pressure would cause the problem your having.

 

Have you checked any of your grounds?

Your check-engine light isn't on or flashing is it?

 

are your 5th and 6th ports operating properlyi would check to make sure both are opening.

 

Is there any loss of power before it hits 6k? or does it just keep making power 'til 6, and then act like its hitting a rev limiter?

 

That wouldn't cause the problems hes having.
And assuming that it dies at above 1/4 throttle regardless of the RPM (which it sounds like is the case) then I would suspect not enough fuel. Was this sudden, or has it slowly gotten worse? If it was sudden I would suspect component failure (bad AFM as mentioned, fuel leak, or maybe bad grounds) if it was gradual, possibly a clogged fuel sock, though that could be the case anyway.

 

If its always at 1/4 throttle regardless of RPM, I would lean toward TPS since 1/4 throttle is about when the narrow range sensor gets maxed out.

Test your TPS since its always good measure to do so anyways.

 

a friend of mine and i took the fuel injectors out of it to see what was up when we went to take them off the primary fuel rail was loose!!!! so the injectors were loose can you believe that ****..
so we tightend everything back the way it was supposed to be and no hesitation 135 in 4th still pulling!!!! thanks for all your help guys!!!!

 

^ There was a plastic spacer between the primary rail and engine mating surfaces correct?

 

ya there was but the bolts holding the rail on were loose... some @#$ before me that had it left it that way.

 

Been there, done that , got the t-shirt.