2.3-16 HIGH idle, slow rpm drop - PeachParts Mercedes-Benz Forum

rg2098 · #1 01-15-2007, 04:04 AM

It's my 87 16V. I was having an intermittent high (1500) or normal idle. No dependancy on temp. The kicker is that the RPMs would fall extremely slow, making shifting... interesting. Well now I have a constant idle of 2500. No idea why. So far...

-New water temp sensor for the injection system
-IACV cleaned and bench tested, operates with 12 volt.
-EHA seals replaced
-OVP tested fine
-Throttle Micro Switch tested fine
-Fuel pump/ cut-off relay re-soldered.

rg2098 · #2 01-16-2007, 08:53 PM

Anybody?

smk_texas · #3 01-16-2007, 09:20 PM

Hi,
Do a search on '190e high idle'. There are several posts on this issue and the causes could vary. After you browse thru the results I am positive you will have some idea on how to fix it.

smk_texas
98 s420
93 190e

rg2098 · #4 01-16-2007, 11:26 PM

Quote:

Originally Posted by smk_texas

Hi,
Do a search on '190e high idle'. There are several posts on this issue and the causes could vary. After you browse thru the results I am positive you will have some idea on how to fix it.

smk_texas
98 s420
93 190e

I have done so. This is a fairly common problem but I have already tried the common solutions. Hence the list in my first post.

david s poole · #5 01-17-2007, 10:53 AM

for the car to be idling that high you have to have a vacuum leak and a big one.have you smoke tested the intake? have you checked the rubber boot on the underside of the fuel injection plenum?

rg2098 · #6 01-17-2007, 07:22 PM

I've checked all areas for leaks. There are none that I can detect. It also appears that when I warm the fuel pump relay behind the battery, the idle drops some.

rg2098 · #7 01-18-2007, 11:15 PM

After about 6 hours today of research on the KE-Jetronic system, here are my findings. The KE system is an electronic hybrid version of the K system. The EHA valve is the primary "output" control of the ECM to the injection system. The coolant temp, ambient temp, throttle position, air meter position sensors are all inputs that basically control the EHA.

I found a test procedure for the EHA. With the ignition on, I should have a 20mA at the EHA, I am currently getting 49mA. This signifies a wrong, or bad ECM. The internal resistance reading of the EHA should be 19.5 +-1 ohm. I am reading 19.

At this point it's looking like I need a 16V ECM.

rg2098 · #8 01-19-2007, 02:31 PM

Anyone know what ECM's will work with a 16V? Will a 2.3, or 2.6 8V version work?

pentoman · #9 07-24-2007, 08:34 AM

Any luck here?
To answer your questino I just read this thread http://www.peachparts.com/shopforum/showthread.php?t=185817&highlight=16v+eha which said the 16V EHA and 8v EHA are the same....

nos16v · #10 01-16-2008, 08:30 AM

Did you find a solution for the high idle slow rpm drop on your 2.3-16? Did you fix the problem by replacing your ECM?

I'm having the same issue with my 86. It certainly makes shifting and stoplights exciting.

NOTE: I've found that if you quickly turn the key back (off) one position to shut off the engine and then quickly turn it back (on) to the run position the idle comes back to 800-900rpm .....but this is only a temporary fix until the throttle position changes and it's back up to 2500 rpm.

davidmash · #11 01-16-2008, 06:27 PM

I had/have a high idle problem as well but not as bad as above. I have replace the hoses and the ICV. So far I have the neutral idle down to about 1050 and the in gear idle (my 16V has a auto) to about 800 or so. I am not sure what else to do. Tied of throwing money at it for incremental reductions on idle.

pentoman · #12 01-17-2008, 03:54 PM

It's worth making sure the idle contact switch on the linkage is connecting properly, and also I suppose the one in the throttle body too. The fact that there are 2 of these, plus 2 air temp sensors, 2 coolant temp sensors (4 if you count the fan switch and the dash guage) shows what nowadays we regard as a crazy system. At least Mercedes fitted it with failsafe 'default' modes, and seem to use high quality sensors and wiring that doesn't fail often. Broken wiring is not unheard of though so worth checking if those switches do work that the signal is repeated at the ECU connector end.