05 BMW X5 4.4i Trans Nightmare
 

Hello! This is my first time posting.

I drive an 05 BMW X5, it belonged to my grandma before she passed. Ive taken on what feels like the most intensive pain in the butt vehicle I have ever worked on.

For 2 months, I've chased a transmission gremlin and no luck. I'm hoping someone here can help me!

So far? I've replaced all wheel speed sensors, hubs, full brakes, suspension.

I've done coils, plugs, valve covers, MAF, vacuum lines, BCM, battery, alternator, wiring, steering angle, fluid change, flex plate, torque converter, trans filter, vanos solinoids & motors, fuel system, injectors, valve springs & seats, cam postion and crank sensors, knock sensors.

I've even cleaned all terminals and wiring around my trans mission.

Now! It has no codes and does not display limp mode. Ive scanned with a snap on sollus edge, torn through my diagnostics.

It will run fine! Acceleration will run through all 6 gears, no slip or shift issue. But when i let off and slow down? It retards itself. For one second I'll have full engine power then pulls back and no more power to the point i can barely climb a slight hill.

What is going on?

When you say "fuel system," what does that include? Does the truck do this at all fuel levels?

I can't see it acting like that and not setting codes ?? Maybe try a BMW dedicated scan tool. You say you let off, it retards itself and for 1 second you have full engine power. Clarity needed.

https://youtu.be/0Cz1wNP8GpY

I uploaded a video for you.

I've used the snap on sollus edge with full uploaded European software.

I hope the video helps.

Try disconnecting the CB, radar detector, and any other add-ons that might be causing problems.

The bmw is used as my work vehicle. Those systems operate on their own electrical bus, alternator and batteries. They do not draw upon the primary bmw system. Volts on the bmw system are a consistent 14v and hold steady. New alternator, battery, wiring harness for whole chassis was replaced brand new. Even the BCM.

As an example of what can happen, the knock sensor wire can act as an antenna for the CB radio and fool the DME into retarding the crap out of the timing. Another thing to check is if the problem occurs when using the A/C?

If the wiring harness was replaced that makes it even more likely that there is a ground or shield missing or wiring not routed properly.

Oh man, reminds me of the limp mode nightmare I had with my E92 with N54 engine. Very dangerous on freeway. I replaced so many parts but eventually it was the DME. Replaced it and the car has been perfect since. You really need a BMW dedicated scanner/software, especially one that would capture shadow codes. I know INPA does.

The radio is an insulated Motorola VHF. This issue was around since the day I inherited it. Before as well after any work was done to it.

It's become quite the love/hate relationship.
The engine is the 4.4i N62 & ZF series transmission. There is no dip and the valve body is solinoid controlled.

AC or not, it goes into that limp-mode like situation.

As for the bmw? It's been already cleared by bmw.
I'm looking more at the TCM. I haven't replace it.

The bmw's KM currently sit at 270,000KM.