Where is the idle control valve on an M104?
 

I've done the search, and everyone talks about cleaning it, but no one says where it's located.

I want to see if cleaning it fixes my idle surge problem on my W124, but I have to find it first.

Any takers?:confused:

You don't have one. Idle control valves are found on CIS cars, yours is EFI. A rough idle on a 104 could be spark plugs, wire ends, vacuum leak, or actuator problem.

Vin

Okay, thanks.

Hopefully I can rule out the actuator. Tech swapped out actuator two years ago to diagnose a problem but didn't solve it (turned out to be the infamous wiring harness).

At almost 116K, it could be the plug wires, but since the problem occurred AFTER the water pump was replaced, I would think a vacuum hose somewhere near the pump.

Check out my thread on my idle problem after water pump replacement.

Out problems our similar, but a little different.

After reading the posts to my problems, and doing multiple searches on idle problems, it was obvious that the usual sources of idle problems are: mass air sensors, throttle actuators, spark plug wire 'ends', engine wiring harnesses, vacuum leaks. I was convinced that one of these was my problem.

My engine wiring harness was replaced at 107,000 miles.

We replaced the mass air sensor and that didn't help, so I put the old one back in.

We checked all the vacuum lines - the ones in front of the engine under the cover that go to the switch over valves - egr, and air pump, and they were connected. There is one vacuum line that is near the water pump and goes under the intake manifold - it's colored (green or blue??) and of small diameter. It was connected.

Bad spark plug wire ends are a frequent problem for idling problems, but mine were fine and also replaced at 127,000 miles, along with new plugs.

We thought the throttle actuator was bad, and I ordered one, but was afraid to install it for fear that it wouldn't solve the problem and I couldn't return it ($961 part).

Took it to the dealer and it was a vacuum leak at the intake manifold seal (gasket). It was causing fault codes of the O2 sensor and air mass sensor, which are likely fine, but the vacuum leak was screwing up their function.

So, your problem occurred after the water pump replacement, like mine, but it my case, it was purely coincidental.

Hope any of this helps.

Fluctuating idle.
 

I have had the same on my 2.8 M104. Exchanged the plugs, wires tec. didn't help. Exchanged the Air mass meter and the OVP, didn't help. In the end it turned out to be a broken wire running from the air mass meter to the ecu. There is a cable running from the air mass meter the is held in a clip at the side end of the block itself. If you have to work on the cables coilds or plugs you need to remove the cover. While removing this cover you twist the cable I am talking about if you leave it in the clip. Do this enough times and the cable will break and give idle issues or stall the car at idle. Have that cable tested.

Greets,

Marc

Thanks for the tip! ;) I'll check that out too!