Engine Bogs Down at Highway Speeds

[ChristineX5]

New member here, thank you for your knowledge and experience.

2008 X5 3.0si (6 cylinder N52) 110,000 miles

We just ran a trailer full of goods up North to our cottage in a brand new Haulmark enclosed 7x14 tandem axle trailer, 2050 pounds empty. (I had just installed a Curt hitch rated at 5,000 lbs, along with the BMW wiring kit. Then I had it coded and all the lights worked perfect).

Not knowing how well an X5 6 cylinder (N52) would pull, I carefully weighed the load as each item came aboard (bathroom scale). Quit at a total of 3,500 to be on safe side and our first trip being 1550 miles.

Amazed with how well it pulled the trailer! Smooth and straight, no issues whatsoever, had plenty of power. Plenty! Easily ran at 70 MPH. Transmission would stay in regular full automatic, and only occasionally would downshift such as going through the mountains. Running 2200-2300 RPM in 6th (top) gear. Starting off sometimes after getting gas, etc., I would start off in manual shifting, to keep the RPMs and torque up. Seemed to like that treatment. All went well the full 1550 miles going up... except no heater!!! And headed from Florida to Wisconsin! (Turned out to be the heater valve under the hood, drivers side, bought a used one on Ebay for $85 and all was well).

But...as soon as we started back to Florida, pulling the EMPTY trailer (but still 2,050 pounds) it felt on the highway like we had a full, huge load and then some! No power up on the highway. Starting off, the rig felt as peppy as always. Going up the on ramps, perfectly fine. But hit 65 and the vehicle was reluctant to engage 6th. And when you pushed on the gas pedal, really push far ---absolutely nothing--- just bogg down!

We ran almost the whole way home in manual 5th gear at 3,000- 3,100 RPM. Sounded smooth and correct, even dare a say purring. No fault codes, no silent fault codes, we disconnected the trailer brake controller (BMW brand new connected to the BMW harness), thinking brakes may be dragging. Thought we got a tank of bad gas. Put in a bottle of Heet and a bottle of octane booster, and always bought top brand name premium all the way home. No help. Just had no power past 60 on the highway??? And boy...did it eat the gas!!! Ideas Please?

Vehicle feels and runs fine even on highway now with no trailer. We have another load to go North in summer. I thought I might jack up the trailer and manually spin each tire to see that they are free??? Always checked the bearing by feeling the hubs along the way. Bearings were always totally cold. Thanks.

[Doug Huffman]

Ideas? DPF, but then I am paranoid of it.

Flow resistance is a square function of velocity, and flow volume rate should be linear with engine speed RPM IIRC. Flow resistance is linear with flow area, the hypothetical clogging of the DPF.

Friction = 1/2 (density) (velocity squared) (shape coefficient) (flow X-section area)

Full weight versus empty weight is acceleration (F=m a), not top speed. Top speed is all drag, the same relation as above.

Cold bearings is good. For long term unpowered bearing condition, look at its tire.

Best wishes. We're at thirty-five days until we head south to Seabrook Island, SC and Inverness, Florida.

[LeiZ]

Did you try manually push it to 6th gear?


Sent from my iPhone using Tapatalk

[ChristineX5]

Thank you for your replies! Yes... I Tried a myriad of combinations of manual shifting and time and again trying full regular automatic. Finally getting back on the Florida flat lands, I was managing to carefully "tease it along" at exactly 62-63 using cruise control in regular 6th full automatic. It seemed the CC could react quicker or feel the nuances of the situation better than I.

I would think this was all normal with the weight and drag of the trailer on a 6 cylinder engine with 110,000. Except it performed so well just weeks prior on the way north for the full 1,550 miles!??? And all the work I did while up North was to replace the defective heater control valve. (If you have the optional rear heat controls, remember you must buy the -two- solenoid model. These units can be rebuilt as well. Easy repair with only a screwdriver, and you DO NOT need to go under the car as a Utube video states! Take one hose off that you can get to with the screwdriver, then twist and lift off the mounting pegs, and then twist to access the other screws on the hoses. Ebay sells rebuild kits for $55. Sure enough when I looked up the hose ports, I could see mangled rubber remains in 2 of the ports, blocking the hot water from getting to the heater core. Diagnosis: Put heater on high full heat full fan and you will feel the 2 hot hoses coming in, but the output hose running to firewall will be cool or only lukewarm instead of hot. Very common failure item. It was frozen HELL all the way from Atlanta North to Wisconsin with no heat!!! (;

I jacked up the trailer today and -removed all four wheels- and tires and did a 5 wheel rotation using the spare (since I had it up anyway). I was hoping to find a tight wheel that did not spin freely, but all had only slight resistance, just as manual states they should. The manual states to adjust them loose, then retighten to where they have slight drag. I know the brakes with the new BMW controller work outstanding so I left well enough alone.

I opted for the Haulmark trailer mainly with going to or left sitting outside in winter up in Wisconsin, the fact it has a ONE piece aluminum roof. No joints to break open from vibration on the road, and then leak later. But it also had the radial tire option which the old guy who owned the trailer yard for 30 years said he much preferred due to a far less chance of a blowout with radial tires. Radials last far longer too.

But overall I'm disappointed with seeing rust already here and there underneath and along the tongue. Haulmark could have done a much better job with paint. So I really let loose with my WD-40 pumper underneath, soaking the springs, door hinges, etc. (It's really a life saver down here in Florida with the salt air and high humidity. I wipe down my tools and yard cutters, etc., after each use. Great stuff for what is basically kerosene! Far, far cheaper by the gallon, and just use a pumper bottle. I use at least a gallon a year).

So any crazy ideas? All thoughts or ideas no matter how improbable would be appreciated at this point!

This may be something to note.... When I'm working in the garage, I hear "something" kick in and run for about 5 to 10 seconds maximum, then stop. I've never timed it, just happened to catch it while out there. Would that be the fuel pump? I know my exact model and year did have a recall on defective fuel pumps in Oct. 2010. Was issued for the E70 3.0 liter N52B30, 6 cyl gas engine. Manufactured 11/1/2007 through 8/31/2008. Replace fuel pump, defective batch during that period that could fail and make steering and braking difficult. Mine is a 4/08 build. Not sure if mine has been replaced under the recall? --Could a weakening fuel pump due this???-- Again...full power running around the gas stations at the exits, and going up the on ramp, but hit 60 and transmission has shifted normally through all the gears, but in 6th (top gear, 6 speed in E70) it bogs down and often shifts back down to 5th. Speed falls off fast in 6th you push the gas pedal down, down, waaay down, and you lose speed and it does not like it one bit, but ease way up on pedal to around the low 60 mph area, and that is it, period! Like someone turned a switch off at 60!

But we know the power is (or was) there from our -very strong- run North with another 1,500 pounds in the trailer! Again...we were very pleased with the power, more than enough.

1. Fuel pump weak?
2. Could I have developed a vacuum leak in an intake hose or in the CCV system? On my wife's 02 330i, she had the cracked intake hose way back on the driver's side by the firewall, where the hose made the bend and was "corregated" but when you looked in the bend, there it was, a 1/2" long crack! Also the CCV hoses were all brittle. And the one to the dipstick (don't I wish a dipstick!) (; was fully broken off. Now when you pull out the dipstick, you can easily hear a noticeable "Thump" when the vacuum breaks by pulling the dipstick.
3. BTW... I had just changed the auto tranny oil (new pan with 7 liters of the ZF fluid, and the transfer case oil (BMW brand) B4 hitting the road. I was getting a scary (1 out of 30 times on normal startup in park) light "clunk" but also the vehicle jerked back an inch or so." That worried me, and I bet the very reason the PO sold the vehicle. The new transfer fluid fixed this issue to instead on vary rare occasion just like someone snapping their fingers, but zero jerking motion.
PS: I tend to get off topic, but when I can help others with issues they may experience, I toss them out there. I apologize to those that don't appreciate these tidbits along the way. (:

Any ideas fellows? The winner with the correct answer gets a neat century old Morgan silver dollar sent to him as a -Thank you- for helping! I do appreciate your time to read all this and any help you can offer! Thank you. (:

[LeiZ]

I'm surprised I read through it. LOL. Nice writing.

When you detach the trailer, do you get the full power back?


Sent from my iPhone using Tapatalk

[ChristineX5]

See by reading by post, you learned a couple tidbits about your M54 engine (same as in my wife's 330i) as well? They are famous for leaking oil at the oil filter housing base. Just a small simple gasket. But the leak gets worse and worse from a couple drops on the garage floor to a big puddle. If you ever do that job, that is when you would want to change out the entire CCV system if old. Much better access! Those plastic hoses from the years of heat get so brittle, they break in your hands! And if up North, install the protected "cold weather version" of the CCV. Has a foam boot over it to insulate it.

Sorry to digress to the M54. Thought it might be helpful to you!??

[davidmaria1]

Just a thought. Would a torque converter lockup issue cause this? I'm no expert on transmissions, if BMW uses a typical torque conv. design, and the two vane discs are not locking at hwy speed, would that where the loss of power could be?

[regdfry]

Seems your issue is the transmission not wanting to shift into sixth gear, with the additional load of the trailer. Yes, it worked well initally. . . Things change.

Since you changed transmission fluid, my focus is on the transmission. Is there too much or too little fluid? Just my thoughts. Good luck.

[ChristineX5]

Thank you for your replies fellows! They are greatly appreciated. Both replies focus on the automatic. That worries me as I know little about these complex units. All I have ever done is change fluid. The fluid change with no pan/filter combo took 7 liters of the good ZF fluid. Correctly filled while running at proper temp. No leaks, not a drop ever on garage floor.

I did not have time for a highway run today. But I did have time for a nearby "Sunday Drive." A half dozen times I took her from zero to 60, paying careful attention to all the sounds and shift points, etc. All seemed normal. Engine sounded very good, shifts crisp and normal.

If this has any value... it did catch my attention. On one acceleration with medium throttle, it had progressed nicely through all the gears, very normal and relaxed in full automatic, but when it went into 6th top gear, maybe ten seconds later it downshifted back to 5th, without any noticeable need to do so??? I remember asking myself... "why did it do that?" There was no need for further torque as my gas pedal was steady?

For those with fuel injector knowledge...

Could I have an injector/injectors that have some crud built up in them? But not enough to throw a code? Remember...we are just light on power on the highway with the 2,000 pound trailer. The wife said it feels fine now up on the highway without the trailer. I have not had a chance to drive it on the highway.


I have also added today a full bottle of Sea Foam in a full tank of gas. (Sea Foam did wonders on my 225 Johnson outboard that is 22 years old. Has not run this good in over ten years, with strong power like new! Just amazing IMHO, not at all "snake oil." All the gas cans for my small equipment (chain saw/pressure washer/lawnmower, etc., now get 4 ounces per 5 gallons. Keeps the gas good too. And everything starts up like new, time and again, and I leave the gas in over winter, year round. But be careful... --less is more.-- It's plenty strong, and work into your equipment gradually to clean everything.

Has anyone here pulled and cleaned the fuel injectors? And the results please? Thank you again. I will keep you all posted so we can all learn what this was.



To address

[wsmeyer]

I'd try replacing the fuel filter.