2000 740i with 125K miles. So the car starts up fine, idles great, and takes off fine. If you try to give it too much gas, it just falls over on its' face and does not accelerate. You can still accelerate modestly and get it up to 70 MPH though. This works for about the first 5 miles and then slowly you loose any the ability to keep it at this speed. It gets to the point where you can only do about 20 MPH. So when it heats up, the condition gets worse. If you just restart the car, it seems a little better for a few seconds. Still at this point, the thing idles steady with no smell of gas (doubt the intake gaskets or PCV is leaking) to the point where you would not know there is a problem. This is a issue that just came on suddenly last week when my wife was out driving, so I doubt the cats are an issue.

In the computer was a couple of codes for lean condition.

OK, after reading a number of the previous posts I changed the MAF and the 02 sensors. No help. Anybody have any other thoughts???

Any smoke coming out the back? And when is the last time you changed the air filter and fuel filter? Is your check engine light on? Have you listened to noise/whistling coming from the vacuum hoses.

MAF and O2 sensors are not cheap, that's almost $1000 put together ... and it didn't even help?
:lol Oh well, at least you have new ones.

Well, as long as your on a spending spree, buy these parts, too:
- fuel filter
- air filter
- 8 spark plugs
- 8 ignition coils
- OSV (aka EGR/rear manifold plate)
- crankshaft position sensor
- camshaft position sensor

Those will probably help.

If it were me, however, I'd just take it to a mechanic instead of buying more parts.

It is not in any limp home mode (so no smoking). New air filter, fuel filter, water pump, radiator, heater control valves, and a bunch of other stuff. Car does not die at all, just bogs when giving too much throttle. The only codes in the computer are for a lean condition on both banks. If I were to diagnose it as a Porsche, I would say that it is a throttle position sensor. This is incorporated in the FBW throttle body on the 740. Do these go bad? I can't find any posts searching that these may be an issue (like the old mechanical throttle bodies on the 850s) Are there any diagnostics for it?

$1000 for the parts?? Not quite. I own a Porsche business so they were only a couple hundred $$s. With 125K and original anyway, it was a good time to change them.

I'm glad to hear that you've got the good hookup for parts.

It doesn't have to be in "limp home" mode to smoke, but if it doesn't smoke, then it doesn't matter either way. No smoke usually means your OSV is okay.

I still say look at these three things:
- crankshaft position sensor
- camshaft position sensor
- DME

But to be honest, I'm only guessing.

You know, after re-reading your original post, I think someone called in to Car Talk with this exact same problem. I did a search on the Car Talk website and found this:

Tom: After 80,000 or 90,000 miles of driving, carbon cakes up on the engine's valves and prevents them from closing all the way. And you notice the loss of power first under load (when you're making the engine work its hardest -- like climbing hills at high speed).

Ray: But there are other things that can cause the same symptoms, like a failing fuel pump, a clogged fuel filter, a plugged catalytic converter or a weak ignition coil that isn't delivering enough spark.

2000 740i with 125K miles. So the car starts up fine, idles great, and takes off fine. If you try to give it too much gas, it just falls over on its' face and does not accelerate. You can still accelerate modestly and get it up to 70 MPH though. This works for about the first 5 miles and then slowly you loose any the ability to keep it at this speed. It gets to the point where you can only do about 20 MPH. So when it heats up, the condition gets worse. If you just restart the car, it seems a little better for a few seconds. Still at this point, the thing idles steady with no smell of gas (doubt the intake gaskets or PCV is leaking) to the point where you would not know there is a problem. This is a issue that just came on suddenly last week when my wife was out driving, so I doubt the cats are an issue.

In the computer was a couple of codes for lean condition.

OK, after reading a number of the previous posts I changed the MAF and the 02 sensors. No help. Anybody have any other thoughts???
Did you get an SES (service engine soon) warning light on your dash? And if yes, have you had the CODES pulled? If, no...then you should really consider having the CODES pulled/read so that you'll know which sensor registered a fault. This will point you in the right direction instead of spending money needlessly in areas that don't have any problems.

BTW, many AutoZones have a reader and will pull the codes for free. If not, you can try your local Indy or take it to the dealer.

I wonder if you have bad CPS sensors (camshaft position sensors). When bad...they can create a too lean condition...and they are VERY easy to replace. The E38s w/Vanos have two sensors...non Vanos e38s only have one sensor.

Here's a post with pics & instructions on how to change the CPS sensors: http://www.bimmerboard.com/forums/posts/63877

Sounds like a buildup of back pressure due to clogged or broken cats to me. My father had a very similar thing on his ford and it was the cats.

My 1999 740il (45,XXX miles) will intermittantly buck/hesitate on hard acceleration at higher rpms. Also sometimes on light acceleration. If you keep your foot into it the car will completely shut down but will not stall out. Once this happens the throttle response or accelerator pedal position has no effect on engine speed like it has been shut off or disengaged and idles around 1500. If I pull over, shift to park, shut the car off and restart it, the car runs fine.

One mechanic replaced the camshaft position sensors, but the problem remains. I replaced the plugs, pre-cat O2 sensors and MAF and the problem remains. I went to another mechanic and he thinks it's the MAF as that was the code he was getting. He thinks that since Bosch had so many problems with their MAF failing that I most likely got a bad sensor - even though its new. I have yet to buy another MAF, though I will soon.

The first mechanic did pull codes for throttle actuator activation and throttle actuator sticking, among others. I opened the throttle assembly housing and sprayed contact cleaner in there. My be I need a new one of those?? However, the 2nd mechanic wasn't getting those codes, so who the f**k knows.

Besides the MAF, it could be ...
- carbon on the valves
- a clogged fuel filter
- a plugged catalytic converter
- failing fuel pump
- weak ignition coils

Make sure you go to a mechanic that specializes in BMW. I think valves that don't close all the way can be tested with a compression test (I'm not sure). A fuel filter is really cheap and easy to replace.

The problem is probably the cats, I've seen a few other people post that they had a similar problem and it was caused by plugged catalytic converters. I've also seen people post that they've had problems with after-market cats, so be careful what you buy (just another good reason to only go to a mechanic that specializes in BMW).

I experienced the same problems in my 97 and it was due to clogged cats, I had Aus Autosports replace them and the problem went away along with the SES light that kept triggering a bad coil on 1-3-6 cylinders.

Lean condition error codes suggest something is inhibiting the flow of gas to the injectors. While it could be CATs or MAF or other inputs to the ignition control system, start with the basics. Have you checked the injector fuel pipe pressure and fuel pump output?

Lean condition error codes suggest something is inhibiting the flow of gas to the injectors. While it could be CATs or MAF or other inputs to the ignition control system, start with the basics. Have you checked the injector fuel pipe pressure and fuel pump output?

Not yet. Good idea though.