124 Newbie - idling speed

[Oreo]

Hi all

I have just moved from a 123 to a 124. The 124 has the 102 engine (I think). It is a 1992 2 litre fuel injected engine. I'm new to the K Jetronic engine and am still identifying the parts but I have an immediate concern.

The engine is idling at 11-1200 rpm in neutral and drops to 7-800 in drive. Is the idle also supposed to be at 7-800 in neutral and being compensated by the idle control system? What is the correct idle speed in neutral and drive?

Does the idle control take a feedback signal from the rpm or does it do its job indepently from a factory setting? What exactly does the micro switch, that I'm supposed to clean, at the trottle link do?

I have plenty of questions .

Thanks
Oreo

[NDavies4]

Someone more technical can probably help you more, but here's what I see with my car (has a M104 CIS-E engine):

Cold
1000-1100 in P or N
700-800 in D or R

Warm (80deg)
700-800 in P or N
500-600 in D or R

From what I've read on different forums this is all normal behaviour.

Did have a problem with my micro switch (think full name is: "Deceleration throttle micro-switch") a few months ago when the garage managed to adjust my throttle linkage such that the switch was no longer activated at idle (i.e. my foot completely off the accelerator). What I saw was the cold idling uneffected, but idling when warm became 1400-1500 and engine temp at idle shot up over 100deg.

All I had to do was turn a little black plastic adjustment screw on the linkage a half turn, which slackened off the cable sufficiently for the spring to pull the arm more forcefully onto the switch. Immediately the switch clicked the idle revs dropped to 500-600!

Hope that's of some help. Also see the thread "300SE high/sticking idle" which has some more info.

[Oreo]

Hi NDavies

That was my problem exactly. A badly installed accelerator cable that was way too tight. About a half cm gap to the switch! Readjusted it an now it maintains idle at 6-700rpm. Thanks a lot!

Oreo