OneBadTA

Last friday i filled up with gas and shortly after it started sputtering and missing badly under load. I thought it was bad gas so i ran it out and filled with fresh and its still doing it. It cruises at light throttle fine and idles fine but it will miss badly as you increase load. You can rev it through 1st with little bit of a miss, you can feel a bit more of a miss in 2nd, and 3rd and 4th start missing as soon as you apply the gas. It can pull some in 3rd but none in 4th. What do you guys think it might be? The plugs and wires are around 1k miles old. Im gonna try changing the fuel filter this weekend if i can get the rusted *** fuel line loose from the filter.

OneBadTA

Also wanna add it has a slight tap in the valvetrain but nothing loud or noticeable when driving. It carries around 45psi oil pressure while cruising when its all warmed up. I dont think a lifter is an issue but maybe im wrong.

86formula

iTrader: (3)

change the fuel filter, check your fuel pressure at the rail

OneBadTA

How do you guys go about checking the pressure? Cut the line and run a T and gauge in between?

86formula

iTrader: (3)

theres a schrader valve on the rail, go to auto zone or advanced auto and rent a fuel pressure gauge and screw it on

OneBadTA

Im pretty sure i have a fuel pressure gauge around here. Ill see if i can find it and hook it up.

OneBadTA

Can i get a picture of the schrader valve on the rail?

stburgpete

dont have a pic but it should have a black cap on it at the back top of the fuel rail. when you take the cap off it looks like a valve stem.

bigj2717

iTrader: (15)

Here ya go http://shbox.com/1/fp_reg.jpg

TunerKiller

Is this fairly common because i am having the same problem.

Please let me know if replacing the fuel filter fixes your problem.

Thanks

OneBadTA

Thanks. No wonder i couldnt find it. I think ill do one more permanent and accessible by using the feed line. What size is the feed line going to the rail?

OneBadTA

oops nevermind. Picture says 3/8". Thanks for the help guys. Ill have the new fuel filter on and try and get a fuel pressure reading this weekend.

OneBadTA

Yeah ill let you know. I hope its as simple as a filter.

TunerKiller

Me too
LOL

OneBadTA

Checked fuel pressure before doing the filter, it was reading 35psi w/ vacuum. Goes up to 40psi when i stab the gas so i know there isnt anything wrong with the FPR. Fuel pressure didnt change at all after the filter change. I havnt been able to drive the car yet but it still has a slight hesitation when i quickly stab the gas at idle. I should be able to drive it tomorrow to see if the problem is fixed. Another thing ive noticed is that after i turn the car off, the fuel pressure immediatly drops to 20psi and steadily drops to 0. Shouldnt it be holding pressure more up around 30-40psi and hold it for a while? If i let the fuel pump prime before starting the car, it builds 30-40psi and steadily drops to 0.

OneBadTA

Anybody know how the pressure should be when the engine isnt running? Is it normal to steadily drop like its doing?

All my other cars, Nissans and Subarus, hold fuel pressure up at 35-40psi for a solid hour or longer when the car is turned off.

I8ASaleen

iTrader: (9)

Do you have a vacuum leak? Is the MAF clean?

OneBadTA

Ill try and clean the MAF tomorrow. I dont believe there is any vacuum leaks. I cant hear anything that would resemble one.

Boman6760

iTrader: (1)

Alldata info on '94 model :


With ignition "ON" and fuel pump running, pressure should be 284-325 kPa (41-47 psi).
A system that does not hold pressure is caused by one of the following:
Leaking fuel pump check ball.
Leaking fuel pump flex pipe.
Leaking valve/seat within pressure regulator.
Leaking injector(s).

A leaking injector can best be determined by checking for a fouled or saturated spark plug(s).


Pressurize the fuel system and observe injector nozzles.
Fuel pressure that drops off during acceleration, cruise or hard cornering may cause a lean condition and result in a loss of power, surging or misfire. If the fuel system is very lean, one or both oxygen sensors will stop toggling and output voltage will drop below 300 mV. Also, injector pulse width will increase.
Fuel pressure below 284 kPa (41 psi) may cause a lean condition. Driveability conditions can include hard starting cold, hesitation, poor driveability, lack of power, surging or misfire.

suicidal racing

iTrader: (14)

your condition sounds like mine almost..you can look at my thread..its the wtf one...i was told opti for me so im getting ready to change it out..my car smells rich when ideling..but i havent put pressure gauge on it,seeing it didnt seem like a fuel problem to me..my did all what the above poster did post above for fp under 41 though..