1990 s13 KAe: studdering when accel. low fuel pressure

[D-oom]

ive been having a problem with acceleration lately. it studders around 2-3.5k rmps usually. if i hold the gas down all the way, i can harldly tell. if i accelerate slowly, it studders moderatly bad. i changed the fuel pump and didnt releave fuel pressure. but when i took the hose off, there was 0 fuel pressure. I DID HAVE A WALBRO 255 PUMP INSTALLED FOR A FEW MONTHS. my motor swap got held up so i swapped it back. bad fpr?

replaced distributor and accesoryscoil, 2 leaky injetors, all sensors on motor.removed emmissionsreplaced fuel pump

there are no vaccum leaks, no visual leaking of fuel under hoodi set the timing with an idle fluctuation between 750 and 1000. i set it to 15 degrees when the idle would drop, so i know its not perfect.

the idle is set at 750. but it likes the jump up to 1500 after a hard drive, then settle down. but i fixed the constant idle fluctuation.

[elwesso]

Did you check your fuel pressure at idle???? best thing to do IMO is T a fuel pressure gauge and watch it as you accelerate and see if it drops off.

[racers4life77]

Hey D-oom did you ever figure out the problem cause i'm having the same issue?

[Acecool]

I had the exact same issue..

What I did..

Replaced the fuel filterReplaced all injectors (They were rusty, and changed only once before)Replaced all FPR vacuum lines with silicone ones..New spark plugsNew spark plug wires (after I had everything running perfectly)

Now it runs perfectly, no hesitation AT ALL

[rogoman]

ive been having a problem with acceleration lately. it studders around 2-3.5k rmps usually. if i hold the gas down all the way, i can harldly tell. if i accelerate slowly, it studders moderatly bad. i changed the fuel pump and didnt releave fuel pressure. but when i took the hose off, there was 0 fuel pressure.

You may have a plugged up fuel filter.

Here's a quick check on fuel delivery:An easy way to test the fuel pump and filter is to disconnect the fuel hose from the top of the fuel filter and insert a long length of spare hose into the top of the fuel filter with the other end draped over the fender going into a catch can placed on the ground. Now turn the ignition key to the run position but DO NOT START THE ENGINE. You should see fuel going into the can at a good rate for several seconds.

If it's OK, then you'll have to tee-in a temporary fuel pressure gauge at the filter outlet for measurement during operation.

The readings at idle should be as follows:- with vacuum hose connected to the fuel pressure regulator: 33 psi- with vacuum hose disconnected from the fuel pressure regulator: 43 psi

[racers4life77]

don't have a gauge, guess that's something else to buy.

my engine is a SR rebuilt, new filter and lines, walbro pump 225lh,new spark plugs with less then 500 mile, check them 3 times, new z32 fuel filter. it does the studdering at 4900rpms and up the same way d-oom explained it oh also chaged the mafs out twice and cleaned them also., don't have any more spare mafs any help would thanked.
Modified by racers4life77 at 6:44 PM 1/17/2007

[rogoman]

my engine is a SR rebuilt, new filter and lines, walbro pump 225lh,new spark plugs with less then 500 mile, check them 3 times, new z32 fuel filter. it does the studdering at 4900rpms and up the same way d-oom explained it oh also chaged the mafs out twice and cleaned them also., don't have any more spare mafs any help would thanked.

There may be a vacuum leak somewhere between the turbo and the throttle body. Also check for a leaking BOV.

[racers4life77]

have no vacum leaks anythng else