Greetings!!!

Have a 190E I am narrowing down my idle problems with. Another member said check the OVP fuse, the 10 amp which I did from the get go, I forgot to mention that. I've cleaned the IAC, and I can make the idle change by moving the adjustment knob, but once I get the idle decent on cold idle.. its up around 1500 rpm when hot.

On the front of the cylinder head, on the intake side are three sending units. The first has two terminals on it, second one ,has one and the third one. The first one, makes no effect if disconnected hot or cold. The second one makes a huge difference when disconnected, especially hot. When hot.. the engine rpms drop.. but it runs extremely rich. THe third sending unit is for the aux fan as far as I can tell. Here is the readings I have:


First unit *two prong* a- cold infinity hot- 13meg ohms
b- cold 95 ohms hot- 95 ohms

between a-b pins cold infinity hot 21 meg ohms

the first measurments are with respect to the cylinder head or ground.

My question for this one is.. does this unit have two seperate sensors to ground in one unit.. or is the change supposed to be between the a-b pins.

being this is a 100.00 sending unit. .I'd just like to know what a working one reads.

I'm pretty sure the second sending unit *middle one* is functioning as it should.. cold I have a reading of 1.6Kohms and hot its down to 257 ohms


Did I confuse anyone? Thanks in advance for the help.. so far it's been amazing the techno info on this site!

73's
Rick
W2ICA

Does it make any difference at all if you unplug the idle control valve when the engine is running??

Gilly

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yes.. I unplug the iac and I can hear the air flow change and the engine rpms drop. I'm suspecting that the engine is not being placed in a cold run or warm up mode, instead is just running as if it was hot. The idle goes up considerably when engine is warm.

Thanks
Rick

Quick update.....

Checked my fuel economy on the car for the first time, was getting 18mpg with mostly local driving. By that I mean trips round town, longest road trip being about 17 miles one way. Only real highway time is approx 1-2 miles on Route 80.

I'm thinking that the computer is not putting the engine into the cold run mode, or cold fast idle. I've compensated for that by turning the adjustment up on the IAC. That's why my idle once it warms up is approx 1200rpm.

I am assuming the that thermo time switch, the forward most sensor's job is to tell the computer to put the engine in warm up mode? I am assuming the second sensor back controls fuel being sent to engine, in that when that one is disconnected I notice a fair amount of black smoke, ie extra rich run mode.

Rick