Can high idle cause high fuel consumption? - 1982 245 w/B230E

My 245 runs very nicely but the fuel consumption seems far too high. I am averaging 7.5km per litre, or about 20 imperial mpg. I recently cleaned the throttle body. It was not very dirty even though it had not been touched in over 40,000km. The car has EGR fitted - the pipe to the throttle body was completely blocked so I cleaned it out. When re-assembled the car idled at about 1500rpm - previously it was about

1000rpm in neutral, 850rpm with drive engaged (3 spd auto). I used the knurled nut below the TB to adjust the idle, but when fully seated the idle is now 1200 in neutral, 1000 in drive. I can't get it below that.

Since I cleaned the TB the other strange occurence is that the engine fires from cold almost immediately but then stumbles, idling at about

400rpm for about 5 seconds, before rising to 1200rpm almost immediately. It runs very smoothly on the highway at 120km/h. Uses no oil between 5000km oil changes.

I have not really paid much attention to the fuel consumption until recently, but 20mpg, averaged across city and highway, seems too high.

The fuel injection does not have an electonic throttle position sensor and no air mass meter. Its an Australian model. Air filter, plugs and oil are all new. Airbox seals well and the heater thermostat in the airbox is open (I don't think it ever gets cold enough in Sydney for it to lose during the day). Fuel pumps replaced last year. Almos new OEM exhaust system. The rotor cap and rotor are quite old but car starts and runs great so can't see any problem there? Thermostat replaced lat year, temp needle in middle of guage.

Based on another post I disconnectde the vacuum hose to the EGR and plugged it, but this has made no appreciable difference.

So, why is my idle so high and how can I reduce it? can this cause the high fuel consumption? What else could cause the high fuel consumption (I do not accelerate hard in this car)

thanks for any advice

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Chris
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