C220 1996 Stalling when braking and ABS light on

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I have a C220 (UK spec) petrol with 270,000 miles (nearly all mine and all done on freeways, so car has been very reliable), but in the last month it has developed three issues (maybe not connected, but not sure).

1) It has started stalling when braking, it seems that it just very reluctant to down-shift to the point of stalling from any gear. If I gradually slow down (just let the car coast) then it will stay running but dips to <500rpm before suddenly changing down, which it does for every gear. I am developing a method of braking/coasting/braking/coasting to get the car to stop without stalling, but it's getting annoying, any help appreciated.

2) The ABS light came on and has stayed on for the last several trips (it comes on when the key is turned to position one and stays on all the time). I have had it go off once after restarting from a stall (I started from Neutral, which was unusual) and it stayed off for the rest of my trip, although it did trigger the ABS when at very slow speeds (felt through brake peddle). Which I understand is typical of a failed sensor.

3)Cruise control failed - Always been very reliable (although don't get much chance to use it on crowded UK roads!!), but now doesn't work 99% of time and for the 1% of time is very erratic and can accelerate or just stop working and the car coasts to a stop.

I got the codes read at my local independant mercedes specialist and fund the HFM fault memory had:-

008 Intake air temp sensor B17 loose contact
022 CC, EFP, actuator signals emergency mode
020 Idle speed control at lower control stop

Also read codes from the ABS controller:
C1102-016 Rpm sensor RA L6
C1314-004 Voltage supply solenoid valves

The mechanic has suggested a replacement Rear Axle ABS sensor, which seems sensible considering the fault code, and I may get a supply solenoid replaced as well. I have checked the OVP solenoid and it seems OK.

I am mainly concerned of the stalling issue, could it be a faulty temp sensor? I have read others having removed the sensor and the car still run. Or can it be the transmission sticking??

Car is still driveable and is booked in for Thursday, but with the mix of faults I could do with some help to keep costs down.

Thanks all and keep up the good work, these posts have saved my wallet on many occasions!!

[mbdoc]

Sounds like the throttle actuator is the key to the problem.

Most likely the cause of 2 of the problems.

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Thanks MBDoc, I will trace the actuator - But does the Cruise control work if the ABS is inoperative? (as I have occasional erratic behaviour, I guess it does).

A mini-update on progress:

I checked the rear axle ABS sensor and it shows open circuit, so either the sensor is dead or the cable is damaged. Guess I'll be spending some time under the car tonight.

The stalling seems to be worse when the engine is warm. I find the worst part of the journey is leaving the freeway after a 25mile straight run, I struggle to keep it alive (I drop it in Neutral and rev for a few seconds before it stays running). Once it is ticking over it is smooth and stable at 650rpm and pulls away well. Could this be the carbon block solenoid valve? [Edit - Not sure about this as I deliberately braked at the first island and it stalled when cold]

Will post back when I have checked out your suggestion.

Thanks

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OK - getting somewhere now. Changed out the ABS sensor and have cured the ABS problem - All working again.

MB Doc, you were spot on with the Throttle actuator. The mechanic did some testing and found it is loosing the programed settings. They would set it up, take it for a test drive and find it had lost it's setting on return. So unless I can fix it myself, I'm looking at reasonable bill for that part.

And you were right about it being the cause of the cruise control issues too. Cruise was working reasonably tonight, but that won't last with the throttle valve going out.

Does anyone know what normally fails - Are they repairable??

Thanks again

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Though I should do an update - I took the Throttle valve assembly out and gave it a good clean (it is pretty close to the oil vent line and does get pretty oily in there). Also did some searching and the most common failure is wiring failure (insulation cracking and shorting out wires).

Having re-wired a bunch of stuff on this car (wing mirrors, phone, immobilizer etc..) I thought I'd check how hard this would be - Unfortunately it is a sealed unit (with centre pin type hex bolts) and the wiring is to molded plugs, so would be a tricky project.

However, since putting it all back together and the garage re-setting it, it is working perfectly (maybe I disturbed the wires in the right way), so I'm holding off on the repair to give me time to source a cheaper part. First sign of trouble and it goes in for replacement.

Thanks all.