190E stalls and idles low. - PeachParts Mercedes-Benz Forum

Spang4190E · #1 11-20-2006, 07:35 PM

I have the same problem as everyone else, My 1989 109E 2.6 engin# 103.942, chassis# 201.029 with CIS, stalls like the key was shut off when it is over 85 deg. C. but starts rite back up. Also it idles low, 500rpms, as soon as it reaches 85deg all the time. these two problems may or may not be related, I don't know. I see you all talking about this but no complete conclusions. I believe it's a heat soke issue, but what part? It has to be electrical.
I've checked fuel flow and pressure. I changed the 4wire temp sensor and the OVP relay.I even added a 1/0 ground wire from the block to the battery.
First question: what tells the engine computer how fast the engine is spinning? The crank sensor?, the mas airflow?, the manifold absoulute pressure sensor?, just the RPM sensor or all in conjunction. What would heat up the most?
Something is telling the computer the engine is spinning faster than it really is and is closing the idle air control motor, I cleaned the IAC with Brake Cleaner, wasn't really dirty. I tried to raise the base idle with the throttle plate adjustment screw under the MAS and the computer put it back to 500rpm, only the TPS advanced base timming, so I put base idle back. When engine cools back to 85 deg. C the stalling stops and idle goes back to 750rpm. I pulled out the timing resistor and this did give me 25 more rpm and alittle more hp.
I know that the Idle control valve is working and the computer is controling idle because the computer raises idle back to 500 when I turn the A/C on.
Could it be going into limp in mode after it heats up? I can drive the car all day on a foggy day and if it never get above 85deg it does not stall. If I disconnect the micro switch on the throttle linkage it idles back up.What does that micro switch tell the computer?
This only happens when its hot, so my next step is to heat up each part with a heat gun until it stalls.
It's all guess work for me, anyone got any ideas?