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I have recently returned from a holiday during which the E220 I have owned for a few weeks operated well for approximately 700 kilometres, except for an issue with harsh and inconsistent idling.

I purchased the vehicle with acknowledged engine harness problems; nevertheless, it appears to have been well cared for and maintained otherwise. The MAF sensor was disconnected, with the cable coiled behind the engine. It had lost all, and I emphasise all, of its insulation. The throttle body wiring had deteriorated into a conglomeration of green dust. The engine functioned effectively; nevertheless, the gearbox performed inadequately due to the malfunctioning throttle position sensor. The harness and throttle body were sent to Si-Lec for refurbishment, which significantly enhanced performance, except for the idle. I examined the codes, which indicated issues with the MAF and air intake temperature sensors (4 and 13). I examined the intake temperature sensor out of curiosity, and it exhibited an open circuit; however, I did not assess the mass airflow sensor. The replacements arrived a few hours prior to the holiday, so I installed them, cleared the codes, and we departed!


Regrettably, it has had no impact on the indolent. Initially, it operates normally in both hot and cold conditions; however, occasionally, when cold, it will rev to 2000 RPM after running for one minute. It occasionally has a slight surge when stopped, which is somewhat unsettling in an automated vehicle. Occasionally, it may stall when shifted into drive; but, once it is off idle, it operates smoothly and possesses ample power. It underwent maintenance a few months prior to my acquisition, and I observe that it has new spark plugs and ignition leads. I replaced the coils after one terminal detached during harness removal, and I have added a bottle of injector cleaning to the system.

Preliminary study conducted during my absence indicated that the fuel pressure regulator may be the source of the problem. I have placed an order, but I am now uncertain. I re-examined the codes, and the initial MAF and temperature sensor codes had reappeared, along by code 8 - 'Illogical altitude pressure signal from the ignition control module.' I have observed that the SRS light intermittently flashes in cold conditions.

Additional reading indicates that the OVP relay may be responsible for the idle issues; however, could this also be the cause of the error codes? Any assistance would be much appreciated!

We possess an E280T exhibiting an erratic idling. It would also experience stalling and consume excessive quantities of fuel. Your technologies and ours may exhibit similarities.

I purchased an additional MAF - not from MB, but a Pierburg insert - which has enhanced all aspects except for the idle.


A smoke test revealed a little leak in the vicinity of the throttle body, which remains unaddressed.

Today, we possess a vehicle that exhibits commendable fuel efficiency, achieving approximately 26 to 29 miles per gallon on relatively brief trips.

However, the variable remains dormant.

We suspect the throttle body and possess a replacement in inventory. It appears to have been restored previously and has been verified as operational.

I conducted a cursory examination of the engine and air intake temperature sensors, and they appear to be functioning properly. We possess replacements, but they have not yet been implemented.

No faults are reported on Pin 8 HFM - single flash.

The lambda probe was replaced in 2023; hence, we do not suspect it at this time.

This may prove beneficial to you and elicit commentary from intellectual individuals.

We anticipate with keen interest.

Wishing you successful hunting.

I have inspected the vacuum pipes, and they appear to be in satisfactory condition, as does the seal between the body and manifold. The technician who refurbishes the throttle bodies in the UK stated that it appeared to be in excellent shape, except for the wiring, which was entirely damaged. I achieved 31 miles per gallon with a combination of driving conditions while accommodating five passengers and their luggage, which I find rather satisfactory. In contrast to your situation, I am encountering error codes, leading me to believe that the difficulties are more likely electrical rather than mechanical or related to air leakage. It is somewhat exasperating, as it operates exceptionally well aside from that issue; nonetheless, I will resolve it one way or another, after which I may transport it on the boat to France!

Is the wiring harness in satisfactory condition?
What are the readings from the O2 sensors?

A new electrical harness and throttle body rewire were installed a few weeks ago. I have not tested the O2 sensor, as I did not receive a code for it; however, I will measure it with a meter and verify its functionality.

Thank you