'85 ur-q Cold Start Problem

["Mike Hopton" <mike@genesis-microchip.on.ca>]

     Just a wee update on the cold start problem on my ur-q.
     
     Symptoms, very unhappy starting below 0C and running lean above 4k rpm 
     particularly noticeable in 4th and 5th. 
     
     Things that made little or no difference, changing the WUR/CPR, 
     changing the fuel metering head, coil and distributor cap.
     
     I hooked up a duty cycle meter to the frequency valve test point and 
     monitored what the ECU was doing for a couple of days. First problem 
     she was running lean so I adjusted the fuel mixture clockwise to 
     richen the mixture at idle. This made an improvement to the cold start 
     problem.
     
     Second problem, under acceleration when the WOT switch operated the 
     duty cycle would drop to 50%. This indicates (on a MAC02 anyway) that 
     the idle switch is still closed. So I'd be happily accelerating away 
     until I hit the WOT switch, which instead of richening the mixture 
     actually leaned it out. Cool thing about this "feature" was the 
     temperature sensitivty of it. Hooking up a voltmeter to the idle 
     switch prior to this showed the idle switch to be functioning 
     normally?
     
     So I replaced the idle switch and the car is running much better in 
     the cold. 
     
     Regards, Mike
     
     p.s. First attempts to install the idle switch resulted in the lever 
     of the switch catching the throttle and holding it open effectively 
     jamming the throttle about 4k rpm. So be careful when you replace the 
     idle switch to make sure the lever on it makes good contact with the 
     bar/pin on the throttle.