I'm working on a 96 t-444e its in a UPS package truck. Its right around 390,000 miles. I am having a problem with the engine wanting to stall when the steering wheel is turned at idle speed. It died on my driver today about 40 times when he was delivering in a residential area with a ton of cultisacs. Last week i installed a new steering gear box, lines , steer shaft, and a power steer pump. I also changed the fluid and filter. This truck is not stalling when i am slipping the clutch at idle, only when getting close to steering stops on a full lock turn. The driver has complained about this before but i could never duplicate problem. I shook and pulled all wiring harness but could not duplicate. I also disconnected the flow switch up by the master cylinder. still no luck. There are no wires around the steer shaft there is nothing tied into electrical on the power steer system other than the flow switch. That switch basically turns on the electric backup brake motor in the event of a engine stall. I checked the codes and there were 3. One was a kam keep alive memory failure. This code is always on in most trucks. Another was engine derated to lowest hp setting, and the other was a ecm failure. I swapped out ecms with a know good truck and No luck there either. I didnt write the codes down when i was at work so i cant give any actual code #'s... has anyone ever experienced a problem like this before. Tomorrow i will check out the Navistar t.shooting book and dig in. but I wanted to try some quick and easy fixes before i really get in deep.

 

I didnt have a ton of time for repair tonight. This truck is still out of service. I did notice when the motor was cold It didnt act up. I am going to try swapping out the ipr valve. At ups we change them out around 80k miles. This one is getting close. Once the truck engine warmed up it started stalling out again. I think that the problem is in the ecm though. I will post up when i find out the root of the problem.

 

You need IPR O rings. When cold, the oil it thick enough not to leak past the worn O rings.

 

what would cause the engine to only stall when the power steering puts a slight load on the engine? It does not stall when i slipp the clutch to put a load on?

 

I can only guess but assume the extra load from the PS pump is causing it to stall. When the IPR orings completly fail you will not get it started when it's hot.

BTW:Have you re-scanned it? Codes numbers would be helpful. I'm not sure about the "engine derated to lowest hp setting" you mentioned above.

 

I scanned the motor, wrote down the codes and left them at work. I am going to replace ipr tonight. I have had a few ipr o-rings go bad. Just let the driver know the let the truck set for about 10 or 15 minutes and it wil restart.

 

Just had a thought, are the brakes powered by the PS pump instead of vacuum? If so, the load is even greater if the wheel is turned with your foot on the brake.

 

Could possibly be the hydro-boost. Also does the truck have a sensor on the steering shaft (usually under the dash)that signals steering request-bumping up the idle?

 

The power steer pump also powers the brakes. I swapped out the ipr valve, no difference there. I pulled in the sister truck to this truck tonight and swapped out ecm's. The truck did not die anymore. I could get it to die if i full locked the wheel and stomped on the brake pedal. I replaced the icp sensor, and checked out the high pressure oil pump psi. Its a little low at idle, I think 450 psi or so. I ordered a h.p. oil pump and will install tomorrow.

No sensor on the steer shaft. only time motor picks up idle speed is when temperature is cold and no throttle action is sensed for a couple minutes. I think it does this untill its 100 degrees. Also the backpressure valve (wastegate) opens up at 100

 

I recieved new ecm on Friday, installed, truck ran better. Took the truck for a test ride around the block and it stalled on me just like before. IHC rep came out friday night to drop of some experimental thermostat gaskets. I'll tell more about that later. I explained to him what i was experiencing, He had never heard of such a thing. I checked out the hp psi again, it is now reading 350-360 when engine hot. He suggested changing out the pump. He also wants contacted after new pump is installed.


My boss got involved towards the end of the week and has called up the dealership we use for warranty repairs. They had no helpfull advice. The boss told me to pull the inspection cover out for the h.p. pump nut. Thought that it may be loose because of a tapered shaft. It wasnt loose. I found a hpop at our indianapolis shop and they sent it up to me for Monday night. I am going to try that and see whats up.

 

finally found the fix.. I replaced the hpop tonight. I ran the snot out of the truck tonight to get the air out, the engine was nice and hot. I couldnt get it to stall to save my life. You can two hand the steering wheel against the stops and it wont stall.

So if you ever have a 444e stalling out when turning the steering wheel, but not stalling when you slip the clutch and load the motor. The problem could be in the hpop.

 

Interesting. Do you have any before and after ICP and IPR% numbers?

 

Very interesting ...We don't this very often...

 

My thoughts are IPR was to slow to react. (sticking)
Or ICP was on the low side at idle.
I would think the pump is good.

Bill

 

Did you change the oil too?...