I've been having an issue for a couple weeks now. Basically, the car will start and run fine. Every once in a while though, it stalls as if its running out of fuel. Pressing the accelerator down causes it to try even more to kill. Once I stop and turn it off, then restart, it runs fine, It has new fuel pump, ignition coil, spark plugs, wires, ICM, battery, opti, and alternator. So where do I start with testing? Also, the engine is a Jasper rebuilt, about 3000 miles on it...

 

Check all ur grounds i had one that did that it had loose ground wires at icm

 

Haven't had a chance to check the grounds yet, but just caught another aspect of this. It kills after 20-25 min of driving, then again after another ~10 min. It's happened 3 days in a row on the way to work, almost the exact same spot. So it's either time related, or the highway is haunted

 

How old is the fuel filter?

 

As far as I know it was changed at the same time as the engine, in august

 

Well, I changed out the fuel filter, and it didn't make a difference. I have noticed that it gets substantially worse at half a tank or less. At stop lights it will idle fine for the most part, but when I accelerate it stumbles and tries to die. I can usually coax it to keep going by being feather-light on the pedal, but even regular acceleration and it stumbles and dies. My next thought it either the FPR or injectors, but when I pull the hose off the FPR it's bone dry, and from what I've read it should have fuel pouring out if it's going bad. Not sure if the injectors are even a possibility actually. The only other things I can think of are MAP or IAT/some other TB sensor, and I have no idea how to test those.

One thing I did notice in playing with it while hot, if I manually pull open the TB butterflies via the throttle cable, I can hear a hissing sound coming from somewhere behind the TB. It stops as soon as I release it, but I don't know if this is normal or not.

 

Check the fuel pressure, it idle, and under load.

 

Fuel pressure at idle is 35psi, WOT is at 45. With the engine off it holds steady at 40psi. I also pulled off the fuel injectors to double check, no dripping while priming the pump.

On a thought, I tested the TPS, and it ranges from 0.67 at 0, 2.99 with the pedal pushed all the way in. From what I've seen, this should be 0.5 for a 93 at 0, and should go up to ~4.5v when floored. Could this be the problem?

 

I would also scan for codes and then clear them. See if it happens again and rescan. Could be temperature related and the temp sender in the water pump has been known to cause issues. Scanning the '93 is easy.

 

I checked for codes, nothing came up. Also reset the PCM, no change

 

90% of the scan logs I review for stock TPS sensors show 0.67V at closed throttle. 94 and up have no adjustment holes on the TPS because the PCM takes whatever volts it sees (as long as its between 0.20 - 0.90V) and sets that as 0% throttle position (TPP). Is the 93 any different than that? I've never noticed the 93 TPS volts at 0% TPP being any different than the other years.

I'd be more concerned about the low volts ar WOT. Are you sure the blades were actually wide open?

 

I rechecked it again this morning, when wide open it was at 4.10. I would swear it was wide open yesterday too though, is it possible it could be intermittently wrong? It was hot when I checked it yesterday, could that cause the difference?

 

A faulty harness connector could cause problems. That's more common with the MAP sensor connector than the TPS connector, but it's worth a check. Wiggle it while you are checking the voltage.

Key on/engine off make sure you have 5V between the black ground and the gray wire. Then measure the voltage between the blue and the black wires while you slowly rotate the throttle open. Voltage should increase smoothly to over 4V, with no spikes and no dropouts.

 

Well everything with the TPS checks out ok, so I'm back to square one. I was thinking MAP sensor, but I haven't been able to find a testing method anywhere

 

Have you tested the coolant temp sensor in the water pump yet ? Has your egr been deleted through the tune ? Running Datamaster would take out the guess work.