Downhill cold stalling

[Perry]

I thought the first time was a fluke, but it happened again today. It stalled while going downhill during the first mile away from home.

The first time, I almost rear ended someone as I wasn't paying attention when the engine stopped and the power brakes went out, but it started up right away, and today, the car required me to cycle the ignition and wait for the glow plugs for it to start.

Both times, the stalling has occurred near the bottom of a long hill while lightly braking. Does the 3/4ton brake booster run off the engine, or is it vaccum operated? Its seems that the two could be related somehow. Any suggestions appreciated.

Perry

[DmaxMaverick]

The stalling could happen if the fuel level was very low. The brake booster is hydroboost, so it does use engine power to operate. Under normal circumstances, the power drain is not great unless you are braking very hard. It should not cause a stall just from braking. Something else is causing the stall if the brake system is normal.

BTW:
If you do have a stall, cranking speed of the engine is enough to power the brakes. The hydroboost should have about 5 reserve applications after the engine is stopped. If your brakes go away as soon as the engine stops, the accumulator (part of the booster) has failed. You can overhaul the booster with a kit, but it is better to replace it. If you have an extended warranty, it is covered.

[Calvin 60]

I have had similar stalls when the truck is just started and run for a minute or two. This is why I question the theory of heat causing the PMD to cause the problem. In my case once stopped and restarted it will usually not happen again. The last time it was two months between stalls.

[JohnC]

My '95 has done that a couple of times. Both times I was using 2nd gear for engine braking and had just put it back up to 3. I think it's a software problem where the computer lets the rpm's get to low and doesn't catch it in time. PITA, cuz there's still a couple of curves left and the power steering cuts out. I've learned to watch for it and it hasn't happened since.

[Perry]

I just got my Sub back from the dealer. Complained about the downhill cold stalling and lower fuel mileage as well as an occasional micro-hesitation on the highway. I used to have an avg of 13.5...now have only had 12mpg over the last three fillups.

As I suspected, all they did was check for codes. But they did check the fuel pressure at the lift pump which was OK. I also had them replace the fuel filter.

I'm getting a PMD isolator kit from Bill Heath for other reasons, but he's thinking that could fix the problem.

Perry