Car not Choking at cold start??
 

Just got this 89 260E. Have already had to replace the fan cluch and the water pump. :rolleyes: Next planned repair is a Cruise control switch replacement. Then my auxilary fan keeps blowing it's fuse and will not work. But before that I would like to know why the car doesn't idle high when it's cold. :( I have to apply gas for the choke session (5-10min) or car will cut off; from being too cold I guess. Any Ideas? :o

Has to be a bad idle control valve or a big vacuum leak. Idle control valve is under the air cleaner housing, two wire plug and two big hoses. Clean it out with carb cleaner, and replace the hoses if they are hard, they leak badly in that state.

You should get about 1000 rpm on initial startup, dropping to the normal 500 rpm in gear in a couple minutes.

If you have to keep your foot in it to keep it running cold, you probably have a serious vac leak that the feedback system cannot compensate for. Check idle control valve hoses, trasmission modulator line, charcoal canister purge lines, and any other vac lines you can find. Typically, by this age all the rubber connectors are shot, so plan on replacing them all. You can use standard vac hose for the stragiht ones, but the "y" and "t" ones I'd get from Benz or an independent, you really need the proper ones.

You will probably need to adjust the idle mixture after fixing the leaks.

Merry Christmas!

Peter

It is you water temp sensor! It tells the CIS-E system when the engine is cold and when to activate the Cold Start Valve as well as the IACV to increase idle. Less than $50 and is the most likely problem. I have posted test procedures for it a bunch of times here so search my userid.

Thanks for advise on the water temp sensor. I've been told there are numerous sensors associated with water temp. which one should I go after. the temp guage works fine.

The cold start valve is controlled by what is called a "thermo time switch". It operates only when temp. is below 59degF and has no effect on the idle speed itself.
The cold start valve is only opened for a few seconds (about 20sec. at -20C) after the engine has started.
So, if your car starts OK, but fails to idle, the problem is very unlikely caused by your cold start valve or the switch triggering it.
Look for vacuum leaks, idle control valve, bad spark plugs, distributor cap, rotor or spark plug wires.
A partially clogged fuel filter or low fuel pump pressure could also be the culprit.

ON the CIS-E KE-Jetronic M103 which is in his car that is not the case. It is called the Water Temp Sensor and is either 2 prong or 4 prong. The two prong one has two individual posts on it and the four prong one has a round plug with four prongs. It measure engine temp to control the fuel enrichment as well as when to tell the Idle Air Control Valve to raise the idle. I have a M102 and had the same symptoms. I have also helped to fix this issue several times by letting people know the procedure to test this sensor! In the 4 prong one you test diagonal pins, two are for CIS-E and two are for the advance as I recall on the 4 pin one. Search and you will find the table of resistance values for the temps you are at. This sensor control the Cold Start Injector as well!

Read through this thread It covers my experiences with a cold-blooded 260E and probably has your fix buried in it.

I'd start with the coolant temp sensor. It's on the top of the head, near the rear, driver's side. It's the one with two seperate contacts. The sensor with a single contact is for the dashboard gauge & the one with three or four turns the electic radiator fans on.

Best of luck,

-20 15.7KOhm
-10 9.2KOhm
0 5.9KOhm
10 3.7KOhm
20 2.5KOhm
30 1.7KOhm
40 1.18KOhm
50 840Ohm
60 600Ohm
70 435Ohm
80 325Ohm
90 247Ohm

There is the table. Yeah I did actually read that thread after I posted as I thought your issue seemed familiar. I mention the Temp Sensor as a start. It will verify at least if it is working before delving into the Idle Control section. I learned the hard way not to screw with that side until everything else is looked at and perfect first. Not that what you mentioned is not the problem just that it is easier to test the Temp Sensor First. With both of use maybe he can get it licked. Of course when I first posted I thought the 260 had the same exact engine as the 190E 2.6! It seems to be but now I am not so sure if there are identical or if the 190's is a newer design than the 260's was.