Low idle at startup ----> ANYONE KNOW THE FULL STORY???

[VeeSix]

Just wondering if anyone knows the reasoning why the L-Jetronic system cuts the idle down on startup/engine cold?
I recently restored a 1988 75, previous owner took out the engine, gearbox and injection loom, so i threw in all that gear from a 1985 90 i stripped a while back, the 90 had the leaded engine with the two plug distributor and ECU code ending in 117, on a running temperature engine i put the idle in at 950 rpm as the manual said 950 + - 50, and on a running temperature engine this is great, i also put new donuts on the propellar shaft so at run temp the idle is as smooth as but on first startup/engine cold until the engine warms up it idles at about 650 which feels a bit too low as at this speed the propellar shaft starts to vibrate and clang a bit, i can only think that the ECU is programmed to idle low at startup to help with the detensioner, DOES ANYONE KNOW THE FULL STORY WITH THIS???

Is it possible to get the idle up from 650 at cold start to 750 or something similar or is it just fully controlled by the ECU???  

 

[Anthony Miller]

If anything my 88 3.0l idles a little higher on cold start.

nice bit of engine pr0n

[Sheldon McIntosh]

Yeah, I've never had a V6 with a slow idle, only when really hot.

Sounds like the leaded and un-leaded engines maybe got different instructions from the ECU.  Not surprising I guess.  Is the intake from the 75 or 90?

[VeeSix]

Intake is 90