Please help with engine Idle speed when warm ok, when cold hunts and stalls.

["nickandkathryntomlinson <nickandkathryntomlinson@xxxx>" <nickandkathryntomlinson@xxxx>]

To All Delorean Tech-heads.
Please excuse me if you have heard of this problem before but I am 
fairly new to the world of Delorean ownership.

I have a problem with the idle speed on my car (Automatic) when the 
engine is cold. It also appears to run rich although this maybe 
associated with this problem.
I have just tuned the engine and have performed the following 
changes/ tests.

Changed spark plugs (plug gaps set to 0.68-0.70mm)
Checked throttle is fully closed (including checking the throttle rod)
Checked microswitch engages correctly and is electrically OK.
Checked Distributor timing and vacuum advance shut off solenoid.
Checked Fuel Canister purge valve/ isolated carbon canister (removed 
and plugged hoses)
Changed Lambda/O2 sensor
Checked Frequency valve `buzzez'
Checked Supply voltage and earth return at Fuel Control Pressure 
Regulator.
Checked for 35 ohm resistance for Fuel Control Pressure Regulator 
heater.
Adjusted Fuel Distributor flap so frequency valve duty cycle 
oscillates between 32 and 45 on a dwell meter. (Note I have re-
plugged the adjustment hole when taken a reading).
Check Idle Speed control valve for operation.
Pins 1 and 2	approx 100 ohms
Pins 2 and 3	approx 100 ohms
Pins 1 and 3	approx 200 ohms
With +12v on Pin 2, momentarily earthing Pins 1 and 3 in succession 
successfully opens and closes the control valve.
Checked continuity of cabling from the control valve back to the 
plugs on the idle speed ecu.
Checked thermistor resistance at idle speed ecu. Reads approx 1.8-2 
Kohms with engine cold, approx 220-290 ohms engine warm.

When the engine is warm the engine idles pretty smooth, varies +/- 50 
RPM at approx.780 RPM.
The engine speed does drop when the air conditioning/ heated rear 
window and lights are put on.
As a further test I have at the ecu end put a manual variable 
potentiometer (resistor) that can vary the resistance between 0 and 
5k on the ecu to simulate the idle speed thermistor. I used short 
cables to connect the other connectors to the ecu using standard 
spade/ blade male female connectors.
I presumed that changing this resistance would make the engine idle 
speed raise and lower as it would change the duty cycle oscillations 
on the idle speed valve but this has no effect.
Am I right in thinking that my idle speed ecu is at fault?
I've check the other connectors i.e. supply voltage, earth, idle 
switch operation, connection back to coil, continuity to idle speed 
valve, protection diodes etc.

My other test tonight when the engine is cold would be to use a 
standard auxiliary air valve used on standard volvos to simulate the 
extra air required for a cold engine. OK, I don't have the correct 
valve so I've improvised (don't laugh) by using a 22mm plumbing 
isolator valve in place of the idle speed valve (in effect a gate 
valve). I tried this out on a warm engine and it raises/ lowers the 
idle speed ok. (Can't imagine screwing this slowly down while in 
traffic !!)

Can anyone advice anything else I can try before I buy a replacement 
idle speed ecu?
Can anyone let me know what the idle speed of their Delorean is at 
cold and how long roughly it is high for? My car is an automatic.

When warm the engine drives really smooth and is a joy to drive, when 
cold I have to use my left foot on the brake.

Thanks all in advance for any further help
Nick Tomlinson ? DOC Member 241.

p.s. If anyone has a "spare" ECU I could try then i'd be v. grateful.
If this is a common problem I could try and source and test a few 
from a breakers yard. Apparrently the same ECU could come from a 
Volvo 200 and 700 series with the PRV engine.