I got this car cheap from a friend b/c it was not running (this is not the car in my sig).. after going through numerous things i found that the problem was the plug going into the top of the opti was completely corroded inside. I put in a new opti and replaced that portion of the wire harness. the car fired up and ran great for 2 days..
then the next day i was driving home on the freeway and the car slowly started to lose power and eventually just died. it tried to fire a few times but would not run..
i got it home and it sat for a couple days.. tried to start it again and it fired up then sputtured and died..
the fact that it fires up tells me that it is getting spark (plus all of that stuff is new)..
i checked for fuel pressure at the check valve and it will squirt once but then won't squirt if you depress it again. (no i haven't checked with a gauge yet.).. i changed the fuel filter but that did not do anything.. i am thinking it is the fuel pump but wanted to run it by you guys before i waste anymore time on this thing..

the car is stock lt1 and has been sitting for months (i did put some stabil in the fuel when i got it)

i scanned it and got the following results (i think some of the codes are stored codes from the opti failure, i only drove it about 6 times for a total of 50miles in the two days it ran, should i clear all the codes and then try to start the car again and then see what it reads?)

P0121 Throttle Position (TP) sensor circuit insufficient signal activity
P0141 Heated Oxygen Sensor (HO2S) heater circuit Bank 1 Sensor 2
P0300 Engine misfire detected
P0410 Secondary Air Injection (AIR) system
P1371 Distributor Ignition (DI) low resolution circuit
P1641 Fan Control (FC) relay 1 control circuit
P1661 Malfunction Indicator Lamp (MIL) control circuit
Pending:
P0141 Heated Oxygen Sensor (HO2S) heater circuit Bank 1 Sensor 2
P0300 Engine misfire detected
P0410 Secondary Air Injection (AIR) system
P1641 Fan Control (FC) relay 1 control circuit
P1661 Malfunction Indicator Lamp (MIL) control circuit

I also checked freeze data:

DTC that caused freeze = P0300
Throttle Position = 0.0%
Engine RPM = 831 RPM
Load value = 2.7%
Air flow rate = 7.76 GR/sec
MAP sensor = 33kpa
Coolant temp = 134*F
Short term fuel trim 1 = 0.0%
Long term fuel trim 1 = 12.5%
Short term fuel trim 2 = 0.0%
Long term fuel trim 2 = 12.5%
Short term fuel trim 3 = 50.0%
Long term fuel trim 3 = 1.5%
Short term fuel trim 4 = missed writing that one down
Long term fuel trim 4 = 8.5%
Vehicle speed = 0mph
fuel system 1 = open
fuel system 2 = open

any ideas?

Thanks!

 

i would clear the codes and check the fuel pressure, the coil/icm and the opti.

 

plug wires?

 

Most of those are stored codes, since the diagnostics for them are not run until the engine is at full temperature, and operating under certain conditions. As noted, clear them. See what comes back when you try and start it up. Your freeze frame data looks OK, since its not in closed loop. Not sure what the reference are to fuel trims "3" and "4".

Multiple codes can also be caused by faulty grounds, particularly for the PCM. Since you have evidence of corrosion on the Opti harness, check the various engine and PCM grounds to insure they are not corroded.

 

opti & coil are new.. i already checked icm and it is fine.. symptoms do not suggest plug wires (trust me i have been through lots of plug wires....lol)..

thanks for the input Fred.. the wiring in this car is questionable at the least.. i'll go through the grounds/etc..
i'm just still kinda stumped as to why it ran fine for two days then just slowly died (keep going back to clogged or failing fuel pump)

thanks again

 

I finally replaced the fuel pump, but... still no change.
The car will fire up then just sputters and dies. The first time you try to start it after sitting for awhile it will run for about ~30seconds and then start to sputter and eventually die. It gets worse and worse each time you try to start it after that. Oh, and it only seems to respond to throttle as you intially start it.

Opti is new, coil is new, fuel pump is new, and fuel filter is new.

I checked the vacuum line to the FPR and it is dry. I tried to run it w/that vacuum line off, no difference. I also tried to run it with the MAF unplugged, no difference.

I'm really getting stumped with this car. It seems like the computer is telling it to shut off, I'm 99.9% confident that fuel and spark are fine.

I did a quick visual on the grounds as Fred mentioned, and all look ok.

Any ideas what could be causing this? I have been searching around here forever and cannot seem to find any definitive answers...

VATS? Vacuum? PCM? O2 sensors? TPS? EGR?

Any help would be greatly appreciated..

Thx
-Neil

edit: I also cleared the codes and then tried restarting the car a few times, no new codes came up...

 

Seems to me that it might be time to ohm test all the injectors to see if you have one or two that are shorting. They will be in the 12.5-12.7ohm range. Anything below 12ohms is definitly suspect. If the resistance gets too low. it will stop the drivers in the computer from firing the injectors and eventhough you have good pressure, no injector pulse. It's worth checking.

 

What does your voltage look like from the time it first starts to the time it dies?

 

Don't look at this as a solution but I had a PCM that would start up and then just die. I replaced the PCM and was good to go so it is an alternative to look at.