Originally posted by DemonSVT:
The 2 things are not related outside of the fact maybe when they were under the hood they damaged or loosened a plug wire. (actually for this job the hood does not even need to be opened.)





"Misfire-detection is another sticky wicket. Obviously, all the engine's cylinders must be firing properly for the emissions-control system to work properly. Most automakers check for misfires by measuring crankshaft acceleration, using the existing crank-position sensor. The controller expects rotational acceleration to correlate with individual cylinder combustion events. Difficulties arise because of the influences on crankshaft rotational speed brought about, for example, by gearshifts and driveline shock, or by driving on rough roads. Some manufacturers are using accelerometers (or ABS, or even an internal engine-controller algorithm) to determine whether the vehicle is traversing rough roads. Knowing that, they can elect to unlock the torque-converter clutch and provide some damping of the driveline shock. Manual-transmission cars can't do this, and a number of stick-shift models have been broomed as a result of misfire-detection problems.

Detecting misfires with a crank-position sensor is also difficult on some engines at high rpm, where the ignition pulse rate is almost submerged by the engine's inertia. Five-cylinder engines, V-10s, and some odd-firing V-6s can generate erratic crankshaft-speed readings throughout their speed range, and even straight sixes may present variances produced by torsional whip. The signals from a crank-position sensor need careful filtering and processing to be dependable, and they need to be dependable if spurious MIL illumination and the storage of false problem codes in the system memory are to be avoided. "

Are you positive they're unrelated Demon?

At least I said I was guessing... In my humble uneducated opinion, elimination of variance produced by torsional whip (which is what a DMD does) could easily confuse the filter.

97 Contour SE MTX K&N 3530, UR UDP, 19# Injectors, mystery mod, FMS wires, Fordchip.com chip, SVT: TB, Flywheel, clutch, exhaust 04 Grand Caravan SXT