RYSO

Hey guys, I'm trying to help a friend out, I searched but didn't find anything usefull. The car is a 1994, S6, JDM with street port, stock ecu, stock 550cc primaries, 850cc Bosch type top feed secondaries with resistors, Walbro, Aeromotive Fpr, Fmic, 7 & 9 NGK sparkplugs, boost at 0.5bar. The problem is that it miss fires at 5000-5500rpm's mostly when engine reached operating temperature. I replaces coilpacks, sparkplug wires, sparkplugs, Map sensor, re-adjusted TPS, new fuel filter, even attached a fuel press gauge on the windshield and went for a drive, still no succes.... i tried to pull error codes but it won't. Any input will be appreciated! RYSO.

Wo:Deep

look at the grounding-connection on the back of the UIM, where you would mount an engine damper.
there is the grounding wire from the engine/ECU-wiring connected with the short 7" wire to the chassis.

Look if the skrew is tight enough..

or look for any other grounding-spot on the car.
I had the same problem.
felt like a fuel-cut... it was only this connection between those two wires.
the vibrations of my engine-damper loosened the wkrew and so the two wires had no perfect connection.

after refastening the skrew everything was perfect!!

look: here you can see the grouding wire to the chassis. on the upper right of the picture you can see the mount (has a yellow dot on it!)



bigger overview:

RYSO

Thank you for your reply.

The ground wires you refer to is mounted and tightened!

I have added 1 thick, soldered ground cable (from battery to engine) and also a thinner one from chassis to coil bracket. It still has all other OEM ground cables.

It mostly does it when motor reaches its operating temperature.

* Note : I also noticed there is no oxygen sensor, they installed a wideband 02 in place of the OEM 02 sensor. Could this be a problem?

RYSO.

baggedoutmazda

try replacing coil pack wiring harness i've read these are a common failed part. i replaced mine, it was fairly cheap from dealer.