I have a 1988 300SEL that is running with a rich fuel mix. It fouled out a new set of plugs within 300 miles. Ran great for those 300 miles though.
At the point the plugs foul, I get a little shimmy in the steering wheel on acceleration, fuel economy drops drastically, and she smokes on hard acceleration (gray/black...soot really).
Also, at start (hot or cold), the engine dies immediately after ignition. The second ignition always takes but is a bit rough for less than a second before dropping to normal idle.
The Bosch fuel injection manual suggests several possible causes:
Hot/Cold Start Failure:
a. cold-start valve or thermo-time switch faulty
b. fuel pump not running
c. air-flow sensor plate rest position incorrect
d. fuel pressure incorrect
e. coolant temperature sensor or wiring faulty
f. insufficient residual fuel pressure
g. fuel leak(s)
h. lambda control faulty
i. injectors faulty or clogged
Poor Fuel Mileage:
a. idle speed, ignition timing, and idle mixture out of adjustment
b. cold-start valve leaking
c. fuel pressure incorrect
I've replaced the cold-start valve and lambda (O2) sensor. Though I understand the O2 sensor is somewhat delicate and easily damaged...will likely replace it again soon.
The car sat mostly still for ten years, racking up 4000 miles from '97 to '07. I've dealt with quite a few dry rot issues (motor mounts, etc.).
I'm curious if there are any known common faults in this model with reference to any of the above.
On a related subject, I've looked high and low for a secondary market manual (Haynes, etc.) for the 300SEL with no luck. I ended up with a Haynes British manual for the E series, 200 thru 320, but have not been able to confirm that this manual covers the same 103 engine. Is anyone familiar with this?
All the best,