I have a 91 z28 305 tpi a/t ok here goes....the car will start and run for abt 15 min then idles really rough if you give it any throttle the car will idle down and die then will not start up again unless it has sat for at least 5 or 6 hours not sure what it is....I have replaced computer(didnt change prom),,alternator,,distributor,,plugs,,wires,,cap,,rotor,,ign.mod,,fuel pump,,stariner,,fp relay,,FPR,,.mech. says injectors are good and anti theft sys. is ok only thing I can remotely think of is comp. prom..


I am really getting tierd of sinking money into this car so someone please help me


thanks steve
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also new tps and other sensors under hood

 

Time to go back to basics and stop swapping parts man.

When it dies, is there still spark?
At the Coil, at the plugs.
If there is spark, is there fuel?
Fuel pressure, injectors pulsing.
Is there too much fuel?
Fuel pressure regulator, erratic injector pulses.
Are all the sensors values within a reasonable range?
Are the ground wires connected to the back of the right cylinder head?
Have you performed a pinout test?

 

yes it still sparks at coil and plugs
FP stays at 40-45 there is fuel injectors are pulsing
not too much fuel no FPR or injector erratications
all sensors good,,ground wires good..........not sure what you mean by pinout test.............also right before the car dies it like it starves for fuel its like the fuel sys shuits off for abt 5 or 6 hours then runs for 15 min

 

sounds to me like classic injector failure once warm, then leaking down flooding the motor, hence no start for 5 or 6 hours.

 

well that was one of my suspicions and ther othe being the prom or the anti theft thing....but my mech (a well known chevy guy round here)says the in jectors are good

 

if it were the injectors "leaking down" you would end up with alot of gas in the oil... well if there was enough gas to flood the engine causing a 5-6 HOUR no run situation


have you replaced the fuel filter? how much flow are you getting from the fuel line... what kind of FP do you have right after the car stalls?

 

filter is new put on last week with the new delco pump I have fuel to the rails per the pressure valve FP is at 42 or 43 when running and drops to like 39 or 40 when it dies ( I think)

 

have you watched to see how long it holds that pressure?

after the car has stalled have you tried another means of fueling...ether? raw gas? to see if it will refire for a sec? or have you checked spark?


next i would ohm the injectors. should be 14-16 ohms between the spades
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sounds like it might be taking a dump when it hits closed loop... for the exact specifics on that you will have to see if someone smarter than I, shows up.

 

holds pressure when it runs havent tried any raw gas or anything like ether ohs on injectors are good think there like 14.64 or something

 

are you saying that the fuel rails will not hold pressure after it the car shuts off?

 

I can't imagine a situation where eight fuel injectors conspire to fail simultaneously. If you are getting a good spark (and you say you are), it is either at the wrong time or you have a fuel delivery issue. Like SpitotRs305 said, try fuel from another source, spray carb cleaner or gas into the plenum and see if it will fire off for a few seconds. Use a test light to make sure you have power and a pulse (ground) signal to the injectors while cranking.
If it won’t fire with fuel from an external source, then it may be getting too much fuel, pull an easy plug and see if it is wet.

 

well after it shuts off I can put a screw driver in the pressure thing and gas come out but it gets less and less

 

So you have not had a fuel pressure gauge on it when it died?

 

my mech did I will ask him abt it tomorrow but the car did the same thing before I had the pump changed and when the car died the pressur dropped to abt 20 psi

 

you have a Fuel pressure gage right? you must use that to check... it is a little more accurate than the screwdriver in the schrader valve...

now stop ruling out the injectors... have you actually tested them... cause the "this mechanic i know says thier good" doesnt mean they are...

but at the moment it really does sound like the problem occurs when the ECM enters closed loop...

what codes are you getting?

 

my dad and I checked the injectors and they were at like 14.64 or something and I was there when the last guy checked the pressure before I had the pump changed but not sure what its at now but no I dont have a gauge as of yet plan on getting one friday

 

There's 8 injectors, and they will not all be the same. Pull off all the connectors, check each one, and write down all the results.

That said, if you pulled one and checked and got 14.6 its not looking good.