Car stalling AGAIN, Updates- none of them good. Options

[rjames]

Drove around for 30 minutes in 80+ degree weather. All arterial roads, so several stop lights, etc. No problems until I was almost home. Car stalled when I stopped at a light. RPMs just dropped to zero. Was able to start it again with a little difficulty and had to keep my foot on the gas to keep it from stalling out again. Power seemed ok though the rest of the way home (I think). It stalled once again at a stop light a couple of blocks from home and then again when I pulled in the driveway. I let it sit for 30 seconds, started it again and it idled just fine. Rock solid at 1000 RPMs. Pulled it into the garage where it sits now.

Prior to today the car has been running and idling perfectly since I went through the FI parts last year, which included installing a 123 distributor, new CHT sensor, a newly rebuilt mps (calibrated for correct afr on my engine), new vacuum hoses, NOS throttle body, rebuilt injectors, new fuel pump, valve adjustment and timing.

I haven’t checked the AFR since last year, not sure why it would change though.
It’s a ‘75 so the fuel pump is in the front, so I can rule out vapor lock I think.

Anyone have ideas as to why it would be stalling?

[rjames]

So I was able to drive around for an hour last night, constantly stopping to adjust the MPS which means there was a fair amount of idling mixed with short drives, engine always running. That equals a very warm engine and there was no stalling.

Just took it on the freeway for 20 minutes, AFR at a steady 13.5 while cruising and as soon as I get off the freeway it of course stalls again. I’m typing this in a parking lot 30 miles from home hoping the car will make the drive back.

I’m almost out of things to try. My car has become a paperweight just in time for summer again.

_____

**Update**
I let it sit for 15 minutes or so and it started right up and idled just fine. Made the trip home and it stayed running when I pulled into the driveway. (IMG:style_emoticons/default/WTF.gif)

Back to basics: Air, fuel, spark, compression.
Under what conditions for any of the four categories above would allow the car to keep running fine with my foot on the gas with no <apparent> lack of power but stall when off the gas?

Air seems an easy one to take off of the list.

Fuel: Lines are new and good and new filter. Verified that the fuel pressure stays in spec even when the car wants to stall. Bosch fuel pump is mounted in the frunk and has less than 1000 miles on it. Injectors sent out for cleaning and are within spec. New injector seals.

Spark: New ignition harness. Tried both stock and electronic distributor. Tried both stock and new coil. NKG plugs and wires have less than 1000 miles.

Compression: Haven't checked, but car has good power and compression isn't an intermittent thing, right?

All vacuum lines replaced, new plenum hoses, intake gaskets, TB gasket, and NOS TB. Verified no vacuum leaks (including plenum). Tried 2 different MPS (both hold vacuum).
New CHTS, also tried swapping with old one.
Swapped relay boards (connections tested good on both of them).

ECU is next on the list to swap out. (I may have already tried this, but I can't remember).

[914_teener]

So I was able to drive around for an hour last night, constantly stopping to adjust the MPS which means there was a fair amount of idling mixed with short drives, engine always running. That equals a very warm engine and there was no stalling.

Just took it on the freeway for 20 minutes, AFR at a steady 13.5 while cruising and as soon as I get off the freeway it of course stalls again. I’m typing this in a parking lot 30 miles from home hoping the car will make the drive back.

I’m almost out of things to try. My car has become a paperweight just in time for summer again.

_____

**Update**
I let it sit for 15 minutes or so and it started right up and idled just fine. Made the trip home and it stayed running when I pulled into the driveway. (IMG:style_emoticons/default/WTF.gif)

Back to basics: Air, fuel, spark, compression.
Under what conditions for any of the four categories above would allow the car to keep running fine with my foot on the gas with no <apparent> lack of power but stall when off the gas?

Air seems an easy one to take off of the list.

Fuel: Lines are new and good and new filter. Verified that the fuel pressure stays in spec even when the car wants to stall. Bosch fuel pump is mounted in the frunk and has less than 1000 miles on it. Injectors sent out for cleaning and are within spec. New injector seals.

Spark: New ignition harness. Tried both stock and electronic distributor. Tried both stock and new coil. NKG plugs and wires have less than 1000 miles.

Compression: Haven't checked, but car has good power and compression isn't an intermittent thing, right?

All vacuum lines replaced, new plenum hoses, intake gaskets, TB gasket, and NOS TB. Verified no vacuum leaks (including plenum). Tried 2 different MPS (both hold vacuum).
New CHTS, also tried swapping with old one.
Swapped relay boards (connections tested good on both of them).

ECU is next on the list to swap out. (I may have already tried this, but I can't remember).

So once at band camp..........


Electrical connector primary circuit somewhere....maybe even at the.fuel pump... loose or high resistance. When it gets hot....poof.

Could be the connector at the ecu is not seated completely.

My
02