This is a long post, but I wanted to be very precise on the details:

Last December I finally bought a car I always had an interest in - a 300E W124 with the 3.0L straight-six automatic. Fantastic car and certainly shows the excellence that is German engineering. It only cost 300 quid, has 160,000+ miles on it, so it's not a show-room example by any means! As such, besides the rust, it wasn't without problems.

First up it was really rough running, that turned out to be a worn-out rotor-arm and distributor cap.

Then the fuel economy was seriously lacking, peaking at 16mpg. From the forums the recommendation was a new fuel filter. This was changed and I am now getting 21mpg, which also from the forums suggests that this is normal.

What I am finding now is the performance is seriously lacking to the point of being disappointed by it. Considering it is meant to have around 180hp and do a 0-60mph in 7.9s it wheezes its way to 50 in around 13s (the speed limit on this island is 35mph! So I'll have to find a quiet stretch of road long enough to get to 60mph). When traveling at a steady speed and I begin accelerating it edges up 100rpm at a time very slowly. My last car was the Accord Aerodeck 2.2i and that was rapid by comparison and that had just 130hp.

What I have done so far:
* New fuel filter;
* New air filter;
* New rotor arm;
* New dizzy cap;
* New spark plugs (Mercedes dealership OEM Bosch parts);
* Used lots of Redex and other injector cleaners;
* Inflated tires to Mercedes maximum guide specification;
* Tried 97 RON fuel, usually 95 RON - both unleaded;
* Compression tested (gives 13 Bar give-or-take per cylinder, hot);
* Checked o2 / lambda sensor - doesn't exist, wiring tucked away under carpet (some posts suggest euro-market cars don't have this fitted?);
* Checked EGR valve - (from reading posts) does not appear to exist;
* Became confused how an EFi car can run without either o2 or EGR... ;
* Got a per-unit price of new injectors - I multiplied by six, and got rushed to resus!;

I replaced the spark plugs as the NGK ones we dark black (dry, not particularly oily). They appear to be NGK's equivalents so I do not think being non-Bosch was the problem. The diagnosis of such spark plug conditions is non-clean burning of fuel or over rich mixture.

One thing I considered was HT leads however the pattern parts shop didn't have suitable replacements so guess that's a trip to the dealership.

So, here I am running out of ideas - perhaps the issue with the spark plugs might indicate something? As mentioned there is no o2 sensor and from reading posts the default action of a failed sensor (or indeed having no sensor connected) is to 'sense' lean and go rich, so how does the ECU know to lean the mixture on such a car?

The engine itself starts alright and runs smoothly at all speeds, most of the forums mention hesitation or rough idling - I am not experiencing that at all.

Would you forum members offer a fellow Mercedes fan your wisdom?

Many thanks,

Glyn B,