Don’t Disintegrate My Mercedes Wiring Insulation

I owned a 1992 Mercedes 400E. I had some of the same troubles discussed in the Made for Monkeys blog about electrical problems.

I too faced the problem of disintegrating insulation on the wiring harness. It was not a big fire hazard, though, since all engine sensor and control stuff was fused. However, a shorted harness could take out the engine computer.

The engine used two coils and distributors, one driven from one of the cams on each cylinder bank. That meant you had to replace a pair of distributor caps. They weren't cheap, either. The cost was nearly $100 each.

The Bosch multiple electrode plugs were pretty well known to be junk. Mercedes actually recommended against their use. They recommended that you use Bosch copper electrode plugs, and you were supposed to change them every 15,000 miles. As long as you changed them at the 15,000-mile mark, the engine ran silky smooth.

Between 1992 and 1993 (the model year of the vehicle in the earlier blog) Mercedes changed its model designation. So the 1993 model would have been designated an E400 and not a 400E. The 1993 model still used the W123 chassis and the M119 engine, though.

With that said, it was a fun car. I got 90 percent of peak torque available from 1,500 RPM to the 6,000 RPM redline. The top speed governed at 155 MPH. True top speed -- without the governor -- was around 175 mph, and that was with the "small" V8 engine.

This entry was submitted by Stephen Mahan and edited by Rob Spiegel

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