91 Z28 Fuel Problem?

[Skid]

first off, thanks to anyone who bothered to click this link secondly, we recently acquired a low-mileage '91 Z28 with a bit of a problem. It fires right up, to about 2000rpm, then drops down like its going to idle at around 1000rpm, only problem is that it KEEPS going down until its limping along about 400-500rpm then sputters and dies, try and give it any gas and it immediately stalls, no change in rpm whatsoever. Fuel pressure problem, right? We replaced the fuel pump and fuel filter and it STILL DOES IT, even with almost 50psi fuel pressure maybe TPS OR IAC could cause this? only thing left fuel-related I can think of is the regulator. I'm no master mechanic, so I'm stumped...anyone have any ideas? thank you anyone

[Hypsi87]

is the check engine light on? if so get us some codes.

Here is how to do it

http://autorepair.about.com/library/...bl-dtcs-94.htm

[Skid]

there's no codes. I wish there were.

is fuel pressure supposed to remain in the rail after the engine is turned off? the gauge slowly creeps down to 0psi, and I don't know if its supposed to...thats why I thought regulator

[Hypsi87]

if something was out of wack with the TPS or the IAC, usually they would send a code, usually. A regulater does not determine wheather or not. fuel stays in the system. it just regulates pressure. If pressure is dropping, then you probabally have a leak in the fuel pump hanger. Do the camaro fuel pumps have a pulsator? I think it's something like a little rubber piece or something like that. I know the GN's have them and they will run like crap and so fourth if that part is bad.

[89IROC&RS]

well, dont know about the fuel pressure, but i had the exact same problem with my 89 IROC. i did a half assed induction service, BG induction cleaner sprayed into the throttle body, cleaning up the IAC valve, and wiping it out with a rag, cleaned out all kinds of black crap, probly resens and carbon build up. but its been running like a champ ever sense. as far as the fuel pressure dropping, sounds like it could be a leak, more along the lines that the fuel pump actually turns off. see if you can get to the connector to the fuel pump, if not the one on the sender itself, then the connector farther up, not sure if its the PCM or what that controls it. but put a test light on it, and watch the light, if it turns on, and then goes out, your loosing the signal to the pump, and there is probly something wrong with your PCM. but id have to go schematic searching to find out.

[4onFloor]

i'd check all the basics first. check for vacuum leaks, stuck pcv, etc.

[89IROC&RS]

well, for a simple no start condition, or poor running, i would agree, but hes saying that his fuel pressure drops to zero, thats an engine output control problem.

[4onFloor]

i dont think it's unusual to have fuel pressure slowly drop when the engine is turned off, could be wrong. secondly, with every problem of this nature that i've encountered, it turned out to be vacuum related. except for this fuel pressure dropping off thing, i think he's pretty much narrowed out the possibility of a fuel related problem. this is TPI right? might check for a plenum gasket leak.

[89IROC&RS]

with it off????? i thought that it was dropping off with the engine on, and then it stalled out because of lack of fuel pressure??? whoops, maybe i should try reading yeah that pressure drop is normal, as far as a vacume leak, ive always known those to cause higher rpms, not a stall, but i havent seen everythign. with that in mind, i am firm in saying that you need an induction service, or your IAC motor is shot.

[Skid]

well, this morning we changed the IAC valve since it looked pretty dirty and the voltage was under specs. Started it up, and it ran great! problem solved so i thought! for only about 15 minutes of course. It revved great, idled great for about 15 minutes and yet the fuel pressure was reading at 20 PSI after it seemed to warm up, the problem came back... idled down to 400rpm, and cut out and stalled as soon as you touched the gas pedal. It doesn't even run long enough to run an intake cleaner through it

[89IROC&RS]

sounds like a PCM prolbem or ICM.

[Mediocrity]

Ermmm...
Idling screw... maybe?...

[89IROC&RS]

not on a 91 older carb'd engines yeah, fuel injection has the IAC which is the same thing, cept computer controled. and adaptive.

[Mediocrity]

Ehm, just sounded like a problem I had on my MX6... would idle and die... and stall.

Mine was loose.

[Skid]

woohoo! I figured it out this morning. When I pulled the INJ1 fuse under the dash and disabled the 1-3-5-7 injectors, the engine actually stayed running on just 4 cylinders... so I put the fuse back, unplugged all the injectors on that side, started it up and started plugging the injectors back in one at a time, all the while revving the engine. So when I got to the #5 injector, BINGO!once I plugged it in, the engine cut out and died! I feel kinda stupid because i checked all the injector harnesses with the noid light but neglected to check the actual injectors for resistance. guess what? all the injectors were at 16ohms while #5 was at 2 ohms.... replaced the injector, runs like a champ! thanks to all you guys who added input and tried to help me out, I appreciate it!