Mercedes-Benz W210 limp mode and rev limit of about 3000 rpm
My W210 will not rev above 3000 rpm, what does limp mode mean?
In limp mode the car's control unit limits the revs and injection to protect the engine. Power disappears and the cruise control usually does not work. The warning light does not always come on. Read the fault codes before resetting, because old codes confuse troubleshooting.
Which faults on a W210 diesel most commonly cause the rev limit?
The most common cause is a faulty mass air flow sensor whose voltage does not change with the throttle. Others are a stuck EGR valve flap, a broken intake air temperature sensor or its wiring, a detached intake flap lever, and a blocked exhaust system. The cause varies, so fault codes are needed.
How is a mass air flow sensor fault recognised and fixed?
First check the sensor's connector and wiring. With a diagnostic tool, the sensor's voltage does not change with the throttle if the sensor is damaged. Cleaning sometimes helps only briefly, so the sensor often has to be replaced. Replacing the intake manifold does not fix this fault.
Should parts be replaced by guessing?
No. The cause of limp mode cannot be determined without fault codes, and blindly replacing parts gets expensive. Read the codes with a diagnostic tool and then check the suspected part, its connectors and wiring. Also check the roots of the injection lines for moisture and leaks.