Every time somebody complains about rough running, everybody else chimes in "clean your DKs."
Why?
My DK motors have not been touched since new. They work fine, only thrown an EML light once with some pretty ancient batteries.
A bad DK will manifest itself either with
1. An EML light and possibly a bank shutdown, and
2.) A VERY characteristic and slight grinding sensation during idle indicating the banks are not mass airflow balanced and thus in need of synching. That's it. Given a few minutes with a warmed up engine, EML will balance the banks automatically during an extended idle - no need for a coast-down.
EML performs a series of power-up and continuous checks against the pedal position sensor and DKs to ensure they're within mechanical limits. Given the age of the design, it's pretty sophisticated and mandated by both the FMVSS and TUV for fail-safe operation. If there were mechanical lash or feedback issues, the comparator function within EML would find it way before you could.
There's a reason Bosch doesn't offer a field reconditioning kit for their DKs. Even though it's a mechanically simple design (for safety's sake), there's a lot to go wrong during reassembly, including destroying the feedback wiper and disc.
I'd rather see folks direct their attention to the more problematic fuel pumps, coils, and plugs. A good fuel pressure check is relative easy, cheap, and informative.
So, check everything else FIRST, and do the DKs LAST. And only if they're throwing an EML light, repeatedly.
Mark in SBA
