PeachParts Mercedes-Benz Forum - Idle air control valve m103 question

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Quote:

Originally Posted by tom42nm (Post 2944761)

So original issue start die, low idle at first not the iac.
I replaced fuel filter, recent dist csap, rotor, nonresistor plugs, o2 sensor.
Tested the eha,
flow tested fuel volume(remove outlet connection on regulator, palstic tubing with hose clamp, minimum 1 liter/40 sec into plastic container),
tested temp sensor (4 prong on mine),
checked for vacuum leaks, replaced all small rubber connectors (not iac hoses)

Plan to check fuel pressure (need fittings), check valves at pumps,
check fuel accumulator this way:

Pinch off the 'return' from the accumulator and disconnect.
No fuel should should leak from the accumulator when you turn the key on, put a pan under just in case it's bad.
http://www.benzworld.org/forums/atta...fuelpumps1.jpg

What I can't figure out on mine:

Have someone start the engine (cold only, warm starts fine).
Airflow plate drops and immediately starts back up, engine dies.
If I hold airflow plate in position (do not let it rise), does not die.
Tryning to figure out that one.
Did you observe the airflow plate in yours at cold start?

Not a good idea to pinch rubber hoses with a hose clamp .Pinching hoses damage them inside as they are one of the oldest pats in your fuel system.

I was just thinking the same thing. I'm not a fan of pinching or clamping anything rubber, I'd rather put the open end in a container of some sort to catch whatever leaks out

My friend as been playing with his front brakes for ages now .Replaced all the items on front rh side .Only the flexi hoses are original . So replaced that and he cut it open to find the inside had closed up as it had been damaged by the hose clamp he had used. Hope you car sorted out soon.

Idle Air Control Valve help

Cold start very low idle and rough idle. Voltage to IACV 2.4v at operating temp.
Measured resistance of the IACV is zero. Replace the valve? Best source for new?

What range are you using for your ohmmeter? You should be using the lowest if not autoranging.
The resistance of the idle air control valve should be around 7.5 ohms.

I just went through testing the IACV again. With 12v direct the unit clicks. I did not remove to see if the valve goes full open. If I unplug the IACV the engine idle drops and stumbles. Remeasured the resistance and read 0 again. Cleaned the posts on the valve and read 8.4. Engine is running OK now. Also cleaned the air intake metering flap and that seems to help although it was not very dirty. Will post again after I try some more cold starts. Thanks for your input

If your resistance is reading 0 (dead short), you should be blowing fuses or burning up wires. Since smoke isn't rolling out of anything when you're applying 12V, I'd be looking at how you're measuring resistance or looking into getting a new meter...

Diseasel, you are correct. I was not making good contact with the valve pins. Cleaned them and read 8.4 ohms. I was thinking that I had an open circuit thereby not getting any resistance reading.

Spray all over the intake side with MAF cleaner or similar to check for vacuum leaks. Make sure to spray the injrctors. I had three pulling air past the seals. Check the IACV hoses for cracks and or brittleness. Replace the O2 sensor uf any doubt. If you smell fuel under the hood, check the EHA. If it's leaking, replace it and retune everything.

I had the dreaded low idle and found multiple problems. Huge vac leak where the injector body boot was not completely sealed was a big part of it, but it still dogged me until I put the O2 and EHA on it and spent an afternoon tweaking the EHA and mixture adjust. Car went from 18mph to almost 23 on the highway at 80mph. Averages just under 21 now in typical driving.

You can if you want to fix two wires to a bulb fix them on the iacv and take the wire and buld in to the car through the bulkhead , you can then view the operation of it with the bulb