Hey All ~

Now that the weather is cold, I've noticed that there is no high-idle of any kind, when I start my 240 in the morning.

Is it supposed to have a cold high-idle? If so, what is the most likely reason it's not working?


Thanks!

 

After dealing with a bad LH temp sensor, it my guess that it has to be really cold (below ~15F) before you'll see the idle increase due to cold temperatures.

 

Please excuse my ignorance here, but are you talking about the temp sending unit that lies underneath the intake assembly?

Also, when I look up parts for this car, it seems that there's a temp gauge sending unit, and a temp sending unit. Are they different things?

I've also noticed that an OEM sending unit is over $200, while some after-market units are only $25. Are we talking about two completely different parts?


Thanks!

 

There should be no high idle for your 240 when it is cold out. The idle is controlled by the idle air control circuit which acts like a feedback control system. The ECU reads the engine speed and adjusts idle air controller to keep the engine speed at around 700 RPM. This is regardless of temperature of the engine or ambient temp.

If you had a high idle when it is cold, it usually is due to a sticky idle air controller.

 

On my 86 (LH2.2), it has two different temp sensors - one for the cluster gauge, and one for the LH ECU. When my LH sensor went bad (high resistance), the ECU thought I was driving around the north pole and the idle RPM's were around 1,500. Under normal cold temps you probably won't notice the RPM's increase.

 

An OEM Engine Coolant Sensor(ECT) should only cost about $80. The sensor for the dash should cost even less. Please post a link/source of where you got those prices.
A failed ECT may enrich the fuel mixture, but should NOT increase the idle. A failed or sticky IAC will. Seems like that may have been the problem you had Bubba240. I have never heard of 240 with a high idle due to the ECT.

 

I am having a problem with a rich mixture at startup and then a REALLY high idle. It won't go down even when the engine gets warm. I thought is was the air control valve.

I pulled my air control valve today and checked its function. It opened and closed depending on which terminals I connected with a 12 volt supply.

I pulled the connector at the control unit and everything checked good EXCEPT the temperature sensor. It showed as an open circuit (not the 200 ohm it should have). I think my LH-Jet 2 is acting like Bubba's did.

There is also a check for fast idle by removing the connector at the temp sensor, but I can't even get to it to remove the connector, let alone replace the sensor, but I think that is my problem. Now, to to get to it??????

Joe

 

What do you have LH2.2, 2.4?
I had a weird experience with a IAC. Took if off, cleaned it, and put it back on plugged in and all and it idled really high. So I put a clamp on it, forcing it to idle correctly. A few weeks later I took the clamp off and it idled fine.
Only conclusion I can draw is my LH2.4 with learn ability finally recognized it was connected?

Your connections on the ECT may just be damaged or loose. Easiest to remove the intake manifold, with a spare gasket around. Mine as well properly clean the TB while you're taking all that off. That needs a gasket too.

 

It is an '83 244 with the LH-Jetronic II, B23F. That was the first year of LH-II. I don't know what 2.2 vs 2.4 means.

I just tried that and as soon as I clamped the hose, the idle dropped.

Now I am back to wondering.

 

I'm experiencing high idle issues myself with my 1993 240. Have replaced the idle air control to no avail. Have checked all vacuum hoses, found some small leaks, and have repaired them. The car idles at about 2500 rpm, but when you come to a stop it will drop down to 1500 to 2000. I can grab the throttle pully and twist it towrds the front of the car and the idle drops immediatly to 1000, and stays there. I have cleaned and lubed the pully parts but this has not helped. I'm thinking throttle positioning sensor, but being able to mannually set the idle by rotating the pully makes me think twice. I have read the above, does this jog anyones brain?

 

That does sounds like the throttle valve switch needs adjustment. It should "click" off and on as soon as the throttle is off/on from the idle rest position.