The Bosch Spark Plugs Cost Me $1,000

Praise for the Bosch Platinum Plus 4 spark plugs in a recent Made by Monkeys blog caught my attention. I put a set of these into my 1993 Mercedes 400E. The vehicle is old, but it's still a great car. While I put in the new plugs, I also replaced the distributor cap and rotors as well as adding some good spark plug wires. I figured I was done with the tune-up business for quite a while. No such luck.

Less than six months after the tune-up, the Mercedes started missing. Since the car is a 1993 model, the computer is not as sophisticated as it is in newer models. I have a special code reader for the Mercedes, but it displayed no faults in any of the systems.

About six months before I did the tune-up, I had to replace the engine wiring harness. This is a common problem with the Mercedes of a certain vintage. The German government dictated that everything plastic in the car had to be biodegradable in a landfill, so the engine wiring was designed to disintegrated at some point. I looked into a new electronic throttle actuator, thinking it might be degrading, but at $1,000 for a replacement, I thought I would wait until it was really bad.

When the car started missing, I mistakenly assumed the time had come to finally replace the electronic throttle. I bit the bullet and bought the $1,000 part. I spent about three hours cussing at the guys who designed the thing as I did the replacement. When it was all back together, I still had the miss. Argh.

I went online to see what other owners were experiencing. I ran across a ton of complaints about Bosch going really cheap with its Platinum Plus 4 plugs. Apparently, they were being accused of being junk. I decided to pull the plugs and see for myself. They were terrible! Almost all the ground electrodes had all but disappeared! Those Bosch Platinum Plus 4s really didn't do the trick!

I replaced them with NipponDenso Platinums, and the car has been perfect since. That was a pretty tough $1,000 lesson.

This entry was submitted by James Kendall and edited by Rob Spiegel

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