After about 7-8 years of having this car off the road it was time to tweak the metering unit minimum fuel setting….

I always felt the car was too lean at idle.  Just a bit rough.  Over the last 2 years during my bare metal rebuild I figured I’d fit an Air/Fuel ratio.

Idle was about 18-20:1  (not good)  – should be 14.7:1 for a modern car and apparently closer to 13:1 for older cars.

So I was encouraged to turn down the A3 (small screw on top of the MU stack).  When I took the cover off I was shocked to find the lock nut on A1 (the largest nut in the top stack) was completely loose – say 3-4mm above turned down.  I was unsure if the lock nut had turned loose or the whole stack (A1/A2/A3) had all vibrated and turned up with the lock not.  Bravely I decided to turn the whole combo down until the locknut touched the body of the MU and then locked it off.

Then I turned A3 down a lot until the idle was in range.  It went so far down that there’s no thread showing on A3 anymore and just enough to lock off with the lock nut.

Now the car idles at about 13:1 and is vastly more perky to drive.  It was hesitating when the throttle was first pressed – or anytime I quickly jabbed the throttle.  That improved a lot after the adjustment but it still feels like it lags a bit more than I’d like.

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