[Engine] Strange idling scenario?

[nuvolino]

Hey there I'm back again with another interesting scenario lol
what I have noticed just recently is that when I start the car and go for a drive pretty much the first time I stop and take my foot off the accelerator pedal the car seems to do this really lumpy low idle almost like when a spark plug isn't working 
sounds a bit like (brrr brrr brrr brrr brrr) and if I try to accelerate a little it almost stalls its almost as though its choking the motor and making it stall? 
the strange thing is if I turn off the ignition and restart the car its totally fine or if I carefully gradually accelerate so as to not flood it with fuel it will gradually become smooth then it will spring back to life with a surge and run normal.

it only ever does it once anytime I drive the car then its good from then on?? strange?

I've tried doing a BSI reset multiple times with no luck

Mind you the one thing that had been done recently was the lambda sensor and it started a little while (a few weeks) after that ? I changed it because I had noticed that the car had been using more fuel then usual and had read that usually the Lambda sensor is the culprit 

getting the old lambda sensor off was a nightmare as it was just about fused to the manifold so I think it had been there for a very long time.

any ideas?

[Col]

Where did you get new O2sensor from? If it was a cheap ebay job, then it is probably the cause.

Have you still got the old one to put back in and see if it cures it?

[jonnie100]

Agree with Col. Cheap O2 sensors are cr*p. I'd have another look at it if you bought a budget one.

[nuvolino]

I haven't got the old one to put back in as it was so hard to remove it took 3 mechanics giving it a go to remove it with special tools etc in the end the third mechanic had to angle grind it off and remove it with a special bolt remover that has teeth to bite into it so it could be removed ... mind you there is always the after cat lambda sensor i could always swap it over and see what that does... the strange thing is that it didn't do it straight after the swap and why would it only do it at the first idle after driving and not all the time also regardless or engine warmth?

one thing I thought it could have been is the Map sensor so i pulled it out and cleaned it and also the throttle body too
and sprayed some RP7 down around the throttle valve inside it and when i went for a drive it seemed to not do it? so tomorrow i will try it again and see if its all good maybe the throttle valve was gummed up?
will report back soon tomorrow

if it is still doing it i will try the Lambda swap see what that does ...by the way anyone know how to test a lambda sensor?

thanks for the replies

[Col]

Could be the heater circuit failed if it only does it to start with- you can test it to see if it has gone open circuit. It will be the 2 wires of the same colour, usually grey.
To properly test it you need live data and watch for it switching lean / rich. You can test the voltage coming out but most digimeters don't react quicly enough. You might find the post cat o2 wiring to short to try a swap.

I had noticed that the car had been using more fuel then usual and had read that usually the Lambda sensor is the culprit

Bit late now, but it's much better to diagnose these things properly rather than guess. It costs you more in the end with guesswork.