Tandem pump??

2004 BEW

I have a strange, intermittent idle problem. Car starts easy enough, and runs great (Italian tune up done on a regular basis). Sometimes when I come to a stop the idle will drop to 600-700 range for a few seconds before self-correcting to 900.

Now that I think about it, sometimes when it was colder, the idle would be rough and low, and the accelerator would be unresponsive until the idle sorts itself out. I have a Malone tune with dynamic idle/EGR.

The only reason I question the tandem pump is because it has a very slight leak. Enough that I needed to reroute the coolant line around the pump instead of under after replacing it a second time.

Oil and fuel filter are done every 10K/20K and a Guru did the timing belt 40K ago. It is more of a curiosity/annoyance at this point and not an OMG what is wrong with my car.

Fixing tandem pump leak is four bolts and a $9 gasket.

Two long ball-end hex key 3/8 drive sockets, 5mm, and 6mm make it a 15 minute job.

My 2004 has occasionally done the slow idle thing ever since new. Unless it does it often, I wouldn’t worry about it.

Thanks, I didn't realize the gasket was replaceable. I seem to remember reading somewhere that the leak was internal and that rebuilding was not an option.

I know the tandem pump had to work overtime for at least the first year I owned it. I didn't know the lift pump in the fuel tank was dead.

Oh, you mean the tandem pump itself is leaking, rather than where the fuel output from it connects to the cylinder head? That’s a different story.

There are apparently kits to replace the seals in the pump, but I have no experience with those. When my original one leaked years ago I just replaced the whole thing.

I will have to take a closer look in the daylight. My concern was how difficult replacing it would be. I wasn't sure if there would be some value that needed to be tweaked in VCDS after replacement.

Sounds like I was over thinking it. Looks like IDparts has them for $240. At least I won't have to give up a weekend golf day to do it.

Thanks for the input!

Nothing needs to be done with VCDS to change the tandem pump. Just make sure the gasket surfaces are clean and bolt it on, then connect the hoses.

I happen to have a tandem pump on the way from idparts. 10% off right now because of Memorial Day. MD10 is the code for the discount.

I did a bonehead maneuver and broke one of the tabs off the drive mechanism of the pump while putting the camshaft back in after replacing the cam followers. Didn’t realize it wasn’t aligned and it snapped right off while tightening the cam bearing caps down. I didn’t want to mess around with trying to fix the old one, since a failure would unexpectedly shut the engine down anywhere, anytime. So I just bought a new one and was lucky that idparts had this promotion.