W124 - 300c3 starting issues !

I recently bought a 1992 300ce sportline in very very good condition. Obviously I did the inital pre-buy check etc and everything looked fine. Also the guy had reciepst of all repairs since 1993 when he bought it.

Suddenly the car has developed some trouble with regard to starting.
1) when engine is cold (engine temp <40 C) - one crack for like 1~2 second the car just starts up.- Idles 800~1000 for some time and the idle drops (i presume this is normal)

but car seems a little resistive as if lacking fuel when you drive out - especially if push the gas a little more - it kind of catches on and is ready to fly!

2) when engine hot (enegine temp 85~90 C) the car will start up in one crank - no problem here

3) PROBLEM - now leave the car for 10 mins or so and come back and crack up it takes like 15 sec of cracking and gas pedal pumping/pushing to start - also it starts rough and then evens out at normal idling. And drives fine after that.

I took it to an independent mechanic (C& H auto, Chicago) - where we changed Sparkplugs to Bosch Platinums - no improvement. {Receipts say flue filter was changed like 3 yrs back with fuel pumps}


Also a voltage check across oxygen sensor was at 0.7 -0.8 - idly I guess it should be around 0.5 - but playing around with the fuel air mixture is very very sensitive and we could not get it at 0.5.

So next it seems as the oxygen sensor - but I am not sure if I am on the right path. The independent mechanic comes highly recommended but he is also trying to figure it out. He suggests - distributor and wire replacement (tune-up) and fuel system cleaning.

I know a tune is something I need to get done since the car was owned by an older gentlemen and sat for 3 months -so far have changed oil/oil filter and topped off all fluids. (Transmission and radiator flush need to be done).

Anyone has an ideas or know what could be the issue?
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