Idle air control, 1991 190E 2.6L - PeachParts Mercedes-Benz Forum

just-n-time · #1 06-21-2016, 12:46 PM

Hello folks, I have a question about the IAC, my car will not start after a rebuild of the Fuel distributor, when testing the iac I find .01 on my meter and no change when cranking engine. My question is where dose the unit get power from? I have seen a test result someplace that had it at .6 to 9.cant remember just where though or even if I am recalling it correctly. My thought goes like this it may get some from the engine temp sender and the mas but some one might set me straight. thanks for the help.

optimusprime · #2 06-22-2016, 04:47 AM

Check out the ovp relay .It will have 1 or 2 fuses on the top .Also give the fuses in the fuse box a turn in their holders. And after a rebuild it can be possible to leave an earth strap off .Check out all the earth points.

optimusprime · #3 06-22-2016, 05:07 AM

Sprry to say this wont stop your engine starting up / It will start with out the conection on the back end of the iac . I would look for bad earth wire in and around engine . Do you do a fuel pressure test ?.Another thing is the IAC gets part message from the engine temp sensor and the OVP relay .Did you get fuel to the injectors ? Can you check the fuses on top of the OVP relay. The OVP is used to fire up the IAC

just-n-time · #4 06-22-2016, 03:42 PM

I have fuel at the injectors I have had to turn the plunger in to a point of 4 thousands usually set around 1 to 11/2 thousands. but I do have fuel now it a matter of enough or not. When I read power at the icv I did so this last time in ohms it started out at 4 and slowly crept to about nine. I have no idea how to read from one system to he other, such as from the ovp to what?

optimusprime · #5 06-23-2016, 04:44 AM

Do you have a spark at the plugs ? As before the ICV wont stop it starting up . Do you think that the workshop manual i have for my M103 260e would help you .

JamesDean · #6 06-23-2016, 12:53 PM

Perhaps unrelated but I just got done replacing all the rubber components on the intake side of the engine.

When I installed the air flow meter and fuel distributor assembly I didn't quite get the AFM boot to seat fully over the butterfly. This cause a massive vacuum leak that would not allow the engine to start.

I was able to get it to start by pressing down on the AFM thus causing the fuel distributor to flow fuel to the injectors.

Later I found my mistake and corrected it and now the car starts normally.

So maybe you have done this too or something similar?

just-n-time · #7 06-23-2016, 01:13 PM

thank you both for your input I have not had your problem with the rubber seal and the butter fly, I have tried to take electrical values at the icv but i just am not sure of the settings ohms or dc volts or some other setting. I have made test's from yellow wire to the r/w wire and y to ground and get different values. oh well the only thing i have not done is try from pin 2 to the iac.

JamesDean · #8 06-24-2016, 01:12 AM

Quote:

Originally Posted by just-n-time

thank you both for your input I have not had your problem with the rubber seal and the butter fly, I have tried to take electrical values at the icv but i just am not sure of the settings ohms or dc volts or some other setting. I have made test's from yellow wire to the r/w wire and y to ground and get different values. oh well the only thing i have not done is try from pin 2 to the iac.

Generally speaking you should never measure resistance on an energized circuit.

I do not believe you can gauge the IACV's function from voltage measurement. I believe you need to measure the IACV's current to get a sense of how much or how little the IACV is operating. To measure current (Amps DC, ADC) you must place the meter in series with one of the connections to the IACV.

I know on my M116, if I disconnect the IACV, the idle speed will ramp up to 1200-1500 RPM.

I believe the M103 works the opposite way but it has been a long time since I played with it. If I remember to do so, I will check my m103 in the coming days here.