300TE-24V Low Voltage at ICV Sometimes
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1991 300TE-24V
300TE-24V Low Voltage at ICV Sometimes
Hi all, I have a 1990 Mercedes 300TE-24V with the following symptoms: low idle when in gear and AC turned on (when turning on AC after the rpm goes a bit down, it does not go back up at all). I tried measuring voltage at the Idle Control Valve (ICV) and its showing around 1.8v. I tried a M103 car and it measured 11-12v. I have tried switching over the OVP, ICV Jetronic module, but voltage stayed at 1.8v.
However when I try to start the car the following day, everything is normal and voltage is at 11v. This idle drop happens ocassionally, and so when it does I have to wait till the following day until it gets normal.
Any suggestions on where else to look?
However when I try to start the car the following day, everything is normal and voltage is at 11v. This idle drop happens ocassionally, and so when it does I have to wait till the following day until it gets normal.
Any suggestions on where else to look?
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190E 2.6L 1989, 190E 2.6L 1988, BMW 535dXdrive 2014, BMW 428i 2015
Both voltages are incorrect. It should be around 5V average. It is a pulsed signal. Are you sure you are measuring correctly? Make sure your meter is in DC mode and the leads are not reversed. Some meters may act wonky with leads reversed. The idle is a strong function of that voltage, around 2V the car would not idle at all, and over 7V it would have very high RPM's.
(1) But clearly you have an issue. It seems like your ECU is at fault here. What happens when you unplug the IACV as the car is running? Do this after warm up.
(2) Does it idle higher when the engine is stone cold? Should be >1000rpm or so.
(3) How many miles on the car?
(4) Does your car have a MAS+ECU or just an ECU? If I'm not mistaken the idle controller is in the MAS if you have one. The earlier models had the idle controller integrated into the ECU.
The transitional KE-jetronic M104's had some electronic issues, particularly the EZL (hard to find). The low rpms could even be related to the EZL.
You will need some diagnostic work as you are doing on this and not be tempted to replace parts indiscriminately.
(1) But clearly you have an issue. It seems like your ECU is at fault here. What happens when you unplug the IACV as the car is running? Do this after warm up.
(2) Does it idle higher when the engine is stone cold? Should be >1000rpm or so.
(3) How many miles on the car?
(4) Does your car have a MAS+ECU or just an ECU? If I'm not mistaken the idle controller is in the MAS if you have one. The earlier models had the idle controller integrated into the ECU.
The transitional KE-jetronic M104's had some electronic issues, particularly the EZL (hard to find). The low rpms could even be related to the EZL.
You will need some diagnostic work as you are doing on this and not be tempted to replace parts indiscriminately.
