Rough Running, Coolant temp sensor?

[italianpride]

Hi all, stored the 91L auto for the winter (outside) got it in the garage bout a month ago but no time till now to work on her till now. what happens now is from a morning start it will fire right up runs good as it warms up. revs are smooth and quick through the range. when it gets up to running temp it will stumble bad when reving up from idle up to about 3000rpm. once it gets above 3000rpm it doesnt stumble at all. also after shutting off when at full temp, it wont start up easy or at all till its cooled down. ive seen similar posts about the CTS but not exact same symtoms. it runs great when cold and just such a drastic change when up to temp, any help is appreciated.

ive checked air intake hoses for cracks and such, connections are good.
last summer did tranny repair, have a few q's ill post about that, also did exhaust and removed cat and dont have O2 sensor anymore, would that cause any problem?

Could it be the gas? prob have just under 1/8, use 91 octane. am in canada and ussually use shell gold gas, but the gas in there now is from petro-canada. does all gas contain ethonol? petro adverts it in theirs, does higher ethonol affect this engine?
I remember before parked it last year got gas at petro and it wouldnt start for a while after, possibly the sensor was going or gone then already?

Thanks, JuLZ

[ChazzyD]

Yes you must have an O2 sensor installed. How else is it supposed to adjust the air/fuel mixture? Start there.
Charles

[italianpride]

Thanks for reply, thing is ive had no )2 sensor for a while drove a few months without troubles, think ive read that some people run without it also but i cant be certain. probably best if i put one in anyways. any other ideas?