car revs fine to red line under half throttle, anything more and it bucks, stumbles and hesitates and wont accel. i know the injectors flow fine (bench tested) , the exhaust is clear ( hollow 1st pre-cat and hollow main cat and no mufflers) . i tried the 3800 stumble pressure sensor grounding the brown wire technique and it seemed to make things worse engine is a rebuild i got from a close and reputable friend had 10,000k miles when it was pulled outta the car running ( sold to an old guy who wanted to do a v8 swap ) so i really dont think its anything with the engine itself HELP!!!!!

 

check the tps for a dead zone. check the secondary injectors.

 

Check the fuel pump.

 

all injectors flow great i cc flow tested on a friends bench tester b4 i put the motor in the car and the fuel pump is cherry i got it from a friend when he upgraded 2 a t2 pump, ill check the tps any other ideas?

 

the two main posibilities are not enough fuel pressure in the lines, or the tps is out of wack.

Since you said the fuel is fine, check and adjust the tps.

edit: just wondering if the fuel filter was ever changed?

 

yea i put a new fuel filter in it, btw what part of the fsm is the tps in? i looked earlier and couldn't find it 4 some reason.

 

Any chance you have a check engine light? (maybe it's blown) Is it an S5? A metering oil pump failure will cause this behavior.

 

s4 is 4A-50 in the FSM don't know for the S5's

 

s4 and ive deleted the oil metering and am premixing

 

check the 5/6th ports. See if they open all the way, also try taking the intake duct off and look at the throttle body. Might not happened to your car but, in my years working on cars sometimes "mysterious" objects find there way into the intake lol.

 

Fuel cut if it's a turbo.

 

actuators went bye bye so its not those and its a n/a

 

I worked on a customer's TII that had a pushed-out pin in one of the secondary injector connectors. It wasn't locked into the connector all the way and when he pushed the connector onto the injector, the pin would either barely touch the injector's pin or not at all. You can't see the wire being pushed out due to the rubber boot and vinyl wrap, so you may need to unplug the connectors and look for this.

 

alright newest update..... it only does it once the engine is fully warm if i "get on it" when its half to 3/4 warmed up i runs like a scalded dog but as soon as it warms up it stumbles 2 the point that i can barely even get home, even if i keep it UNDER half throttle

 

Any results from the TPS check? Listen for clicks or just bite the bullet & make a check lamp.

 

Also check voltage at the fuel pump connector under the rear carpet. You should see somewhere around 9 volts at idle and battery voltage under accel. Fuel pump resistor/relays do fail on these cars.

 

i used a check lamp on the tps but i havent done a resestince test yet cause i suck at using a multi meter and 4 the puel fump ive got it hard wired to the ignition

 

he has an S4 NA the only S4's with dual pump voltage is the TII.