104 Engine -x320- 1996...HFM (?) Troubles
 

Opened the engine and replaced the hydraulic lifters...cam followers. Put it back together. Timing chain positioned per manual....advance retard set to the right when reassembled.

Started it up and it runs as if it's missing....rough idle.

After looking a little further...there's mention of HFM memory erase and reset.

What's that about? I'm electronically ignorant regarding engines.

Thanks IN advance for insights!

Don't worry about the reset. None of the adaptations that you would reset would cause a misfire.

I would change the three resistors under the coils. Only one is bad but I doubt I could tell which one without serious testing. A proper scan tool will tell you burn time and voltage but the spark is often very similar, it just doesn't make it to the spark plug.

If you drive it long enough you will set a misfire code on the cylinder involved but may not set a light as MB cuts the fuel when a misfire is detected and OBDII only requires a light when the fault causes a 1.5 times failure of the federal standard for exhaust gases.

Thanks Steve!!

If I get what you're saying, there are three coils, off of which three wires go to plugs. Are you referring to the rubber tubes under the coils that connect to the spark plugs.

When apart, the insulators were kind of shot. Hard, flaked at the bottom allowing what I sense would be a gap for grounded sparking. Wiring Harness received a bit of electrical tape.

Any test short of sticking my fingers into a 400v arena?

Wiring Harness Woes
 

I did as instructed.

Replaced wires of wiring harness with their plugs. all new resistors on all 6 cyl.

W O W ! ! !

Running like a gazelle!

S M O O T H.

I did unwrap the harness and all of the insulation was baked and flaked!

(Seems obvious, over the head, enclosed in a cover........looks like an oven to me!?!)

The easiest way to work in there is to flip the resistors over onto the intake, which puts a full 180 degreed torsional force on the wires. Hence, rigid insulation craccks exposing wires to grounding or shorting out!

I did find flexible wiring about an inch or two out from the engine. I soldered on dealer available new plug and wire sets on. (against advice)

I await a wiring harness from Germany and will replace upon arrival.

Thanks for the input.

I read someones quoute.

Wiring Harness...Wiring Harness....Wiring Harness.