Engine Bogs Down at Highway Speeds

[ChristineX5]

Mr. Meyer...isn't that a built-in part of the fuel pump inside the fuel tank? As I mentioned...on occasion when in the garage, I hear something "kick in" and run for about 5 seconds and then stop. Only once in a hour in the garage, but I have heard this several times on different days. Thanks!

[ChristineX5]

I decided tonight just to open up the driver's side of the engine compartment and "see what I could see". Gave me a chance to look over the intake "bellows" (far, far better design, far more robust than the M54, this being the N52 in my 08 X5. The CCV hoses looked very nice as well. I still shook on all that I could get to. All were good. Thought maybe there was a "throttle control valve" to clean like on my wife's M54 but I did not spot one. Two DISA valves, front and rear, fancy!

Always bearing in mind... what did I do that changed things from the way up North when the engine ran strong and perfect for 1550 miles, and immediately on the way heading south with an -empty- trailer, it had no power at all, bogging down, on the highway.

The only thing I touched was the heater control valve. I replaced the defective one for a good used one. That's it.... Ready???

Well...since buying the vehicle I have noticed the workmanship has been shoddy on engine bay repairs. A screw missing here and there, a cover not on correct, etc. Well it turns out WONDER BOY...whoever this mechanic way, decided it is FAR, FAR TOO MUCH WORK TO TIGHTEN THE INTAKE TRACT CLAMP on the throttle body. So he just pushed it on the throttle body and called it a day. Yes...the screw was extremely difficult to tighten from under the intake tract but again just took time and patience.

I bet when I was wrestling out the old heater control valve that has a mount of only 2 pins it rides down on, and having to twist it by the hoses to get at the lower hose clamp screw, that I cocked the LOOSE intake housing on the throttle body just slightly. Just enough to introduce a slight air leak. Not enough to throw a code, but enough to introduce extra air down below the MAF? I won't really know until spring when I head North, but I bet I got it! This would all make sense regarding the above facts. (:

[the_ulf]

Originally Posted by ChristineX5

I hear something "kick in" and run for about 5 seconds and then stop. Only once in a hour in the garage, but I have heard this several times on different days. Thanks!

self-levelling rear suspension?
that would be the compressor

[ChristineX5]

Had a chance today to run the X5 out on the highway for 30 miles. HUGE difference in power and pickup. Now the IDrive controller shows an average of 22MPG instead of 11MPG being the best!!! More power than it ever had during any time of my ownership of this vehicle. So that INTAKE BOOT that goes to the throttle body was leaking air or should I say "pulling air" in at that loose joint for as long as I have owned the vehicle. Lucky the lean condition did not harm anything.
As I mentioned in a prior post from yesterday, I found the entire intake boot loose. The big hose clamp on the throttle body was not at all tightened at the bottom. The intake assembly was just pushed on loose! Some shoddy mechanic taking the easy way out.
And sure enough...this is the area of the engine bay I was working on when I changed the heater control valve. So I bet I bumped the intake and cocked it over a bit farther than it was, causing the loss of power to be noticeable when pulling the trailer up at highway speeds only on the way home.
--Thank you again-- to all those who contributed to helping me with this issue. A strange one indeed, but we got her fixed!!! (:

[ard]

And not a single code nor engine light? Amazing.

[ChristineX5]

Nothing, not a blink or a beep! I even checked with my code reader to see if any "silent" codes were set. Again nothing. I agree that is strange. Thanks Ard.