Last chance... accleration problem

[BrettInLJ]

I have posted this problem on this and other boards for the last couple months and no one has been able to put their finger on the problem yet. I am going to take it to one more shop on Monday, and if they can't diagnose or fix it I am going to cut my losses and get rid of my E39. It just doesn't feel like the same car to me anymore.

Info:
1999 540i 6-speed, 56k miles.
Recent work:
Water pump replaced, Trans fluid changed, valve cover gaskets replaced, and new spark plugs (the right kind) @ 50k miles
Power steering hose replaced, Dinan CAI filter replaced, and CDV modified @ 54k miles

At about 54,500 miles I started noticing that the acceleration would hesitate now and then. For example, I would shift into 3rd gear and after completing my shift and pushing the acclerator, the rpm would go up to about 4500 or 5000 rpm without much acceleration, hesitate, drop back about 50 rpm as the acceleration "catches" and then I would get acceleration that felt about 60 - 70% the normal amount. At first it happened occaisonally in the higher gears (4th and 5th), but now it is constant and noticeable in all gears except 1st. The acceleration feels sluggish in all gears, even the the problem does not manifest.

I don't get any Check Engine light, and the shop's have looked for codes and found none. I took it to a repuatable shop, and they said they didn't notice it when they took it on the freeway. I have a feeling they are not used to the feel of a 540i 6-speed.

I am desperate for any ideas as to what the problem could be. I though clutch, but the clutch pedal and shifting feels normal.

[Sands]

My guess would be several things


ignition coils - will take a while to throw a code
camshaft position sensor - vanos isn't being told to do the right things
o2 or cat problem - do you notice this cold, all the time or just hot?


The position sensor are fairly inexpensive and easy to change. bmwtips.com has the instructions I think.

The coils are pricy so you may want the dealer to doagnose them. BMW did have some problems with these. So has VW and other german makers

The o2 and cats should show a service engine soon light.

If you have a good unk yard, most of these parts can be had for cheap. swap them out and see if the problem goes away. then buy a new part or live with the used part.

[BrettInLJ]

My guess would be several things


ignition coils - will take a while to throw a code
camshaft position sensor - vanos isn't being told to do the right things
o2 or cat problem - do you notice this cold, all the time or just hot?


The position sensor are fairly inexpensive and easy to change. bmwtips.com has the instructions I think.

The coils are pricy so you may want the dealer to doagnose them. BMW did have some problems with these. So has VW and other german makers

The o2 and cats should show a service engine soon light.

If you have a good unk yard, most of these parts can be had for cheap. swap them out and see if the problem goes away. then buy a new part or live with the used part.

I notice the problem all the time now, whether it is hot or cold. I hope the shop can diagnose it on Monday. :(

[FireWalker]

Just a guess, but it sounds like an Oxygen uptake sensor, or anything else regulating fuel oxygen mixture.
Also have you tried removing the CAI and DINAN stage II, to see if problem persist with OEM setup?

[humanoid]

Call Lee at Cunningham BMW in El Cajon (619-442-8888). You will get the receptionist but ask to speak with Lee the tech out in the back. She will connect you. He is the only person, I allow to work on my car. Hes a good guy and honest. Tell him Ray with the dinan 540 said to give him a hollar. He will lets you know when the best time to bring it in will be and it gives him a headsup to think about your problem.

The issue, as you are aware of, points to several things that can cause this. They can test your back presure for a cat problem and see if it has thrown any codes and go from there. My advice would be to take him for a drive and show him. Dennis is the service advisor you will speak to when you bring your car in if you decide to. He's a good person too.

I know this can be frustrating but hang in there. If you need a lift home from Cunningham I may be able to help let me know.

[BrettInLJ]

Thanks for the offer. The problem is sounding more and more like clutch slippage, and I'm going to verify this with a shop today. This happend shortly after my CDV was modified by a local shop (I thought they were going to remove it completely). If it is not the clutch, I will take you up on that.

Call Lee at Cunningham BMW in El Cajon (619-442-8888). You will get the receptionist but ask to speak with Lee the tech out in the back. She will connect you. He is the only person, I allow to work on my car. Hes a good guy and honest. Tell him Ray with the dinan 540 said to give him a hollar. He will lets you know when the best time to bring it in will be and it gives him a headsup to think about your problem.

The issue, as you are aware of, points to several things that can cause this. They can test your back presure for a cat problem and see if it has thrown any codes and go from there. My advice would be to take him for a drive and show him. Dennis is the service advisor you will speak to when you bring your car in if you decide to. He's a good person too.

I know this can be frustrating but hang in there. If you need a lift home from Cunningham I may be able to help let me know.