My 2000 yukon xl has service engine soon
light on and is running poorly it turns on but
looses power as soon as i put in drive. I
changed the coils spark plugs and looked at
the lifters they seem to be fine the codes that
are coming up are po300 and po200 please
I think you might have a bad injector. One code may indicate an injector problem and the other is a misfire code which could be caused by a bad injector. Since these are generic codes I can't say which one is the problem. I might start with a good fuel injector cleaner.
I too have a 200 GMC Yukon XL and if you put anything other than Shell cheap gas in it runs so not good, wants to stall at the light, not much power, sounds ruff ect... Same gas every time! And the Cheap stuff.
Spark plugs also. Mine didn't do well with the Newer ones. Too much spark for my 2000 GMC.