My 1986 190e 2.3-16 has a stalling problem. It occurs at operating temp and only when the weather is 90 and above, even humid days. As I drive along and press the clutch to disengage the trannny at a stop light etc, the rpms drop to less than 300 then go up to normal 1000 rpm. Sometimes the car stalls completely. It starts right up though. This gets worse with the A/C on. Any assistance would be appreciated. Could it be a fuel pressure problem? The car has the original fuel pump and accumulator. Only the fuel filter has been replaced at regular intervals. I also think that it might be a vacum problem. Could it be a fuel pressure problem? Your assistance would be appreciated. Joe

check the fuses on the overvoltage protection relay and make sure its firmly plugged into your socket..its located behind your battery and has one or two fuses on top.

Any problem with any sensor input will cause the CIS computer to go into FOM(fixed operation mode). At that time idle may be at 1200RPM or your case 400RPM. Most likely & common problem is the air flow position sensor. Of course that is if the computer is getting power from OVPR.

Does the air flow position sensor need to be replaced often? I understand that it is an expensive component. As far as the ovp relay, I have replaced it already and there was a little improvement but the problem still exists. Joe

Joe

They all do this. Good luck!

The idle stabilizer is the likely culprit. The computer sends a signal to it to vary it's dwell (it is a rotary valve that flips open/closed at a specific rate). When you turn on the A/C, the idle stabilizer is supposed to spend slightly more time open, increasing the idle speed (same with when it's cold). They gum up and stick. Locate this device. On the 2.3 8V, it is between intake runners 3 and 4. Remove it. Spray carb cleaner in one of the air connections while holding your hand over the other. Shake and repeat. Poke something plastic (soft) into it and make sure the valve is free to move. Plug the valve back in and turn the ignition on (dont start the engine). You should see the valve flip back and forth. If not, meter the connections. You should see voltage come up, then drop. If not, the computer, or one of it's inputs (temperature sensor probably) is faulty.

Benzfan is right on. The last time I was plagued with an erratic idle speed I unplugged all the sensors in the fuel and ignition system to include removing the two computers. All the individual components in fact checked out okay. I cleaned the connections, cleaned the item Benzfan mentioned and put everything back together and it ran for the next 8 months before needing idle speed servicing again.

MB has two diagnostic manuals for this engine. the "Mercedes-Benz C.I.S.-E Engine 102.961 & 102.985 Diagnosis & Adjustment 1984 -'86" (part no. 102 584 0110)which is for the 190 E 2.3 and the "Service manual Supplement Engine 102.983" (part no. S-2347-SUP) for the 2.3-16 and items that differ from the 2.3.

Robby

I checked the throttle position switch and noticed that the small rubber boot under the switch was completely ripped and the switch itself was rusty. I ordered a new switch and will see how the car does. What does this switch tell the computer? When the throttle is closed, right? It activates another function under deceleration right? Thanks, Joe

Bingo!
 

I replaced the switch last night, took me 10 minutes and a 7 mm wrench. It cured the idle problem, it idles steady at 1000. Thanks Benzmac and all who answered the post. Joe

Joe-

I'm having trouble locating the throttle position switch, could you hand hold me through finding it? I'd really like to try your suggestion, this idle 'bog' before revving is driving me up a wall. THANKS!

Squirt some oil on the linkage. I've seen them hang and they don't activate the idle switch.

67 912 Sunroof
78 280CE
72 T-II

throttle position switch...
 

Hi Paul,
Here are a couple pictures I just took of the TPS:
http://www.tokuhara.net/cars/misc/throttleswitch1.jpg
http://www.tokuhara.net/cars/misc/throttleswitch2.jpg
You can see the part number: 002 545 01 14

TPS
 

Glen-

THANKS for making it ridiculously obvious for me, I need all the help I can get. That's what I thought we were referring to, mine looks OK.

Joe, how much was the new TPS? Now, this cured your erratic idle, but how about the over 90 degree stalling problem??? I just took mine to the drags up in NH last week (see the 1/4 mile post) during that week it was insanely hot here, like 100 or so. While my times were, er, OK, the f'n thing kept stalling EVERYWHERE. Go to stage @ the timing light? Stall. Go to move ahead in lane? Stall. But it's fine now that the tems are lower, idles nicely @ 1000. Did the TPS cure this????

Thanks again for being the "guinea pig"...

Great picture! BUT that is the decel shutoff switch, the throttle position switch is on the butterfly, that is at the lower portion of the intake manifold. Glad that fixed your problem.

Hanging my head in shame...
 

M.B.Doc,
Thanks for the correction. That would explain why it fixed my problem of the RPM's falling too slowly during gear changes...