Intermittent stalling problem.

[Explorer_PL]

This is bizarre but here it goes:

Every few months, in the same spot on my way to work, my truck will just stall. Now, I am pretty sure it's not UFO or some other forces It always happens at the end, and at the bottom of a very long hill (0.5 mile probably) where I ride on the brakes most of the time. First, I thought maybe I was low on fuel and the pump just sucked in air when the fuel just moved forward, but it happened again few times with at least half or full tank. After restarting it I am good for the next few months. It's quite dangerous situation sometimes, as at the end of the hill, I need to make a left turn, and then I realize that I do not have power steering aid from the pump. Somebody suggested a vacuum leak from brakes ? But I checked all the houses coming into intake and they are solid.

Any ideas ?

 

[Flag Gibby]

I really think that based on what you are saying that you have a vacuum leak in/at the brake booster (since you say you have checked all the hoses) and the engine loses enough vacuum idling down hill to stall it when you go back to the gas.

 

[Flag Gibby]

ExplorerPL, just wondering if you have had a chance to test the brake booster to see if there are any issues there? Also, is the AC on when this happens? Just trying to think of anything else under those conditions that might draw a good amount of vacuum at just the right time to cause the engine to stall.

Just had another thought, since it is occasional and does it and goes away for a while it might be a bad reading from the throttle body sensor so you could try cleaning the throttle body to see if it has some carbon buildup on it.

 

[Flag Gibby]

Don't know why I didn't ask this before, have you checked for any DTC's after it happens just in case the system has a pending code of some sort to help isolate the issue?

 

[Explorer_PL]

Gibby -

Thanks

need to try to pull the codes right away after it happens, but no light comes on so not sure if there are any stored. Most likely the AC is on.

How could I test the booster ?

 

[Flag Gibby]

Here is a link to probably the easiest test that I have come across that doesn't require a vacuum gauge except for the last part to verify the amount of vacuum being supplied to the booster.
http://www.roadkillcustoms.com/hot-rods-rat-rods/hot-rod-power-brake-booster-test.asp#axzz34HsWHmbZ