I'll try to describe this symptom......

I have a '99 528 with the 4 speed auto. Every once in a while I like to pull the automatic down into 2nd and run it through the gears. I really don't abuse this car or over-rev it in any way.

In 2nd gear it powers right through 4K and above smoothly, no problem. When I slap it up into 3rd gear and continue to accelerate -- I notice the engine RPMs fluctuate between 3K and 4K.

I don't know if it's the colder weather or what. Anybody experience something like this ?? Got any ideas ??

Pull the codes to see if anything is there but it could be Vanos seals or a number of other causes.

Does it seem like its kinda "shifting" like the RPMs are on the rise, then they kinda stall and go down a little before rising again? My car does that if you dont have your foot all the way down. Even though you are in 2 or 3 on the gear selector make sure you have the kick down switch engaged all the way (behind the gas pedel). This is my first automatic in a very long time so I figured it was a normal annoyance of driving a slushbox.

Two things going on here--one is that ,when your going through the RPM variance between 3000 and 4000 the DISA valve is actuated--second is that the Vanos seals may make the timeing of going through the RPM variance seem more sluggish. I don't know what shape your DISA valve is, you can check it while at idle by placeing your left ear on it and if you hear a sound like marbles in a can sloshing around, presume it's bad. There is a gent here that offer's a rebuild kit for the DISA--it's a fraction of the price for a new one. On the Vanos Seals, if they are the same ones that came in the car--I know for a fact they are bad and need to be changed out--trust me on that one--The OEM seals can and will wear out in as little as 10,000 miles from what I have been lead to belive.

Thanks for the reply poolman, as always -- I value your input. I know your part of Virginia......I've been to Smith Mountain Lake many times.

The VANOS seals are on my list. I don't know if they've been done before I got this car. I'm probably going to let my local Indy do this job. What would be a good estimate for that job.......6 hours ??

I replaced my Vanos seals and still experience what I beleive the OP is describing. I have not done my DISA but it is on the list, would a bad DISA sound like a rapid tapping sound?

The puzzling thing is this wavering of the RPM between 3K and 4K -- it only occurs when the trans in in 4th gear. It's smooth in 3rd gear right up thru the higher RPM's. Fudman is right. I gotta pull the codes.

Thanks for the kind words Fivedriver--we gots it pretty cozy down here in the Blue Ridge Mts. Nline6,When a Disa Valve is about to go you can hear it without having your ear right up on it--if it's that bad be mindefull that there is a metal pin located on the tip of the valve--if it loosens up to a point it can go through the intake manifold and be pulled into a cylinder--if that happens, you will be spending thousands instead of a couple of hundred making all right with the world again.

I am hearing that "rattle-can" noise under the hood. But there's a lot of strange noises under there with temps in the teens these days. I'm going to raise the priority of the DISA valve on my list of jobs.

Question -- Is the DISA replacement a good job to combine with the VANOS Seals ?? Are we working in the same part of the engine bay ?? Not dis-assembling things twice ??
'Bout how many hours for both ??

Originally Posted by FiveDriver

I am hearing that "rattle-can" noise under the hood. But there's a lot of strange noises under there with temps in the teens these days. I'm going to raise the priority of the DISA valve on my list of jobs.

Question -- Is the DISA replacement a good job to combine with the VANOS Seals ?? Are we working in the same part of the engine bay ?? Not dis-assembling things twice ??
'Bout how many hours for both ??

These two jobs are completely separate and do not involve any common tasks.

Replacing (swapping) a DISA is a 15 minute job. Remove two screws, pull the DISA, replace with new DISA, insert two screws. Done. Repairing the DISA (replacing the pin) will add about an hour. Search for Gary+DISA+upgrade.

Replacing your Vanos seals will take 4-6 hours, depending on how fast you work. This job requires removing the fan shroud and fan clutch, opening the valve cover and removing the Vanos. Search the Beisan website for the DIY.

That rattling sound cound be your Vanos bearings. Or it could be your DISA flap about to come off. If the latter, stop driving and fix it now. The consequences of a DISA flap failure are a dead engine.