lasvegasZ28

I have an issue. My 94 z28 shuts of randomly, sometimes i take the gas cap off and the car starts to hessitate untill it dies. Sometimes when is parked it shakes alot and I step on the gas and it doesnt take it it sounds like is choking on it. (New pump, filter, spark plugs n wires, engine temp sensor,air filter, :/ any sugestions?

Injuneer

What is the fuel pressure at idle? What is the fuel pressure under max load (on the road, WOT, max RPM)? Do those numbers change when you remove the fuel fill cap? Are the results any different if you power the fuel pump from the fuel pump prime connector next to the PCM? Have you checked the voltage at the connector at the rear axle? Has the EVAP system been checked for cracked hoses?

Did you replace any of those parts in response to sprecific DTC codes?

mrmint69

Was it happening before the new pump, which is why you replaced it? Samething with the plugs and wires. Did you have this problem for a while and changed all the parts listed, hoping to fix your problem?

lasvegasZ28

First of all thank u guys for the replies. About the pressure readings I dont recall the numbers but I had a mechanic checked it and it was good. The reason for my second new pump is that the pre owners put a new one but they did a terrible job didnt even atache the pump to the assembly properly. I put a new one on and it went bad within a month, so this is the latest one and its getting good pressure and all. Evap hoses are not leaking but one thing I havent check is the EGR valve. Today I replaced the fuel pressure regulator and the knock censor, tomorrow I ll drive the car for a while and see how it reacts
Also took the fuel filter out and find some sand in it. i dont get why the car shuts off if I take the fuel cap off, I been checking today to see if it does it again but it havent and the gases coming out of the tank are back to normal yesterday it was too much. I was also told it could b a shocked opti, oh and the plugs where changed because I noticed the passanger side plugs where the original from factory and the wire where all different kinds of them,

lasvegasZ28

Sorry for the late replies guys I been working and the little time I have I spend it fixing my car. I have O2 censors but I dont know if the old ones have something to do with the problem, they are expensive and dont wanna use them if I dont need them

Injuneer

Why are you replacing parts? Are you scanning it for codes, and checking the pressure? You indicate the fuel pressure was checked by a mechanic, and "it was good". Why replace the fuel pressure regulator, if that's the case? Why did you replace the knock sensor? That isn't going to make your engine stall. And if the knock sensor or the wiring was faulty, it would set a code in the PCM.

Spend the money on diagnostics and analysis, not by playing parts replacement roulette, hoping to get lucky.

lasvegasZ28

Every part replaced was done because of scanning the car, knock sensor was rusteted out, fuel pressure regulator was changed because after 3 fuel pumps I wanted ro get as many fresh parts since the car was parked outside for a long period of time here in las vegas, engine temp sensor was also scanned as foulty,plugs, wires, filters is routine maintnance. What none has told me not even a scanner is why the car shuts off it does not show any codes. Today I been using the car and no problems at all, last time it stalled was about 1 hr after filling the tank, I dunno if gas was bad quality or if that ll cause the stalling.

lasvegasZ28

Also fuel tank had dirt in it so a good cleaning was nessesary. Now my question is, does a foulty opti cause the car to stall and why so much pressure in the tank? No more codes have been deteted