91 4L (EFI) On Gas (Auto) Idle Issue when warming up

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Hi,

I have recently purchased the above.

Everything was fine (other than replacing the cv's.... boy was that fun!) Hwever it had an older gas system (vacum controlled) so I had that upgraded to electronic control.

Now This was done 2 days after purchase so may or may not be related!

Problem is the vehcile starts idling lower and lower then stalls just before the engine gets up to operating temp. It idles fine when cold and fine once warm.

At first I thought maybe an air pocket in the cooling was causing the gas converter to freeze so I tried only running it on petrol still happened.

Only in the morning (seems to be worse on cooler mornings but we haven't had much real variation in temps to test this)

It happens taking the kids to school.. just as we are getting to the drop off zone or stop at the crossing out the front.

Apart from that it runs fine! Very smooth idle normally and once you restart it (turns over a fair bit to restart) it will be fine

Any suggestion??