WHat to check first?

tia

Lou.

You should get the codes read and that might tell you the problem.

Thanks for the reply Chris. No codes, no MIL or SES on dash either.

Sorry, I forgot to mention.

The mass airflow sensor might be your problem.
They make a spray cleaner I used once with success.

But you should wait for one of the more experienced guys to answer.

Ok

Bueler?

I would think a dirty/worn MAF would cause a lean condition. Does that car have a OBDII connector on it? If not then I don't know how you would read any PID's or codes. If it was OBDII then you could read the fuel trims and O2 voltages. My guess is a bad O2 sensor. How do you know it is very rich?

__________________
1998 C230 330,000 miles (currently dead of second failed EIS, yours will fail too, turning you into the dealer's personal human cash machine)
1988 F150 144,000 miles (leaks all the colors of the rainbow)
Previous stars: 1981 Brava 210,000 miles, 1978 128 150,000 miles, 1977 B200 Van 175,000 miles, 1972 Vega (great, if rusty, car), 1972 Celica, 1986.5 Supra

Faulty engine temperature sensor . Sending wrong information to ecu .ECU will make it rich if it stuck and not leaning off the mixture after its hot. Do a check on it with a dmm.

What's going on to suggest you are running rich?

__________________
Mike Murrell
1991 300-SEL - Model 126
M103 - SOHC
"Fräulein"

Strong fuel smell and black soot on exhaust pipe

My car is OBDI not OBDII

Check out the thread and the links in the thread that I provided. It shows how to build the LED code reader and how to use it. And buried in there is a pdf copy of the code book that includes your model. This book is slightly too large to link in this forum.

http://www.peachparts.com/shopforum/tech-help/107630-e320-16-pin-dtc-charts-inc-pin-8-pin-14-a.html

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95 E320 Cabriolet, 159K

Check the fuel pressure regulator , a vacuum line runs from it to the intake manifold removed it and check if fuel is being sucked into engine , its located at front of fuel rail round with a c clip holding it in , I just found out my 94 e 320 s was leaking , failed smog because of excess hc, replaced it and passed smog check