My 2001 Excursion stalls upon an abrupt stop. It is easy to avoid stalling by stopping smoothly, but there is definately a problem somewhere. I cleaned the MAF sensor, has new IAC, renewed grounds from chassis to frame. I never renewed engine to chassis; never could find it.

I was wondering if the physical action of stopping abruptly disturbs the engine to chassis ground. Could that cause it to stall? I was considering using a jumper cable from the negative battery terminal to the engine block to rule this out.

What else could cause this?

 

Could be a number of things:

Vacuum leak screwing up the IAC function.
IAC valve malfunctioning.
Torque converter not releasing.

For the last one, try shifting to neutral while at a speed that would normally trigger the stall, verify neutral condition, then (safely) brake sharply and see if the problem happens or not.

 

Shot in the dark:

Another thing to think about is the interaction between the brake power booster, and engine vacuum. Try projectSHO89's suggestions first, and then see if the brake booster is holding vacuum for a bit after the engine is off.

 

I put 3 cans of seafoam in a full tank. About 1/2 of it is gone. It has gone from stalling every time to stalling less than 10% of the time when I'm intentionally trying to get it to stall. It does have a fluttery idle sometimes with no stall. It stalls in reverse too. I tried to experiment with the neutral thing but couldn't get it to stall. I'm guessing I do have a vacuum leak, and a possible problem with the PCV valve because of a recent increase in oil consumption. I guess the seafoam cleaned the injectors to such an extent that the systems recovered without stalling. I ordered the 90 degree vacuum hose that is supposed to fail on these engines. When it comes in, I will take it to my mechanic. I hate working on cars in the cold.

 

Just a thought, but I've had my work truck with the same transmission stall on occasion when the transmission fluid is low.

 

Does the device (solenoid?) that unlocks the torque converter operate by vacuum?

 

Nope. It's electrical, controlled by the PCM.

 

Mine stalls only if I go from forward momentum to reverse when the fluid is low.

 

Did a full system scan, and it is showing a U1262. I had to update the driver on my Blue Driver to get it to do a full system scan.

I'm guessing that when the engine changes position abruptly something is causing a short in the wiring harness.

 

Turns out it was low line pressure in the transmission. Had Jiffy Lube drop the pan, replace the filter, and flush with SYNTHETIC ATF. Must be synthetic. Fixed it immediately. I found reference to this fix in a TSB. Kind of hard to believe, but it fixed it. Jiffy Lube now carries synthetic ATF, and they are the only quick place that will drop the pan and replace the filter.

 

Wow, thanks for reporting back!

 

What TSB is that?