Ive been having a few issues that have me stumped. I am going through oil bad. 1 quart a fill up almost. not leaking, not plenum, idk. i got 180pds of compression on all hole but one with 160. Now on occasion it starts to ideal like crap. surging reving up to 2k rpms on its own down to 400 then it fixes itself in about a min. I got a o2 sensor high volts code and heater circut error on bank 1 sensor 1. Is this whats causing it? Maybe MAP sensor? any help is needed

 

The failing oxygen sensor needs to be replaced, but that's not causing the oil consumption -- it's the oil consumption that killed the sensor, and will soon kill your catalytic converter if it's not already a goner.

If it's not the plenum gasket it could be something as silly as a failed PCV valve or something as ugly as a cracked head. Yank the spark plugs one at a time to determine if one or more is oil fouling. If so, and neither the plenum gasket nor the PCV valve is failed, it's time for a leakdown test.

 

got a new pcv valve and the plugs are pretty new and seem to burning normal

 

Where did you get the PCV valve? The only ones that are good are the ones from Mopar.

 

it was the best one auto zone had...the old one was gunked up with oil

 

PCV valve from the dealer or from a parts store? They're one of those parts that you want to buy only from the dealer, as much as it pains me to say it. Aftermarket PCV valves just aren't worth even their cheap price these days. That said, if you're not seeing a great amount of oil on the plenum belly pan then the one you've got isn't failed.

The oxygen sensor would account for ugly idle quality and increased fuel consumption, but the oil consumption has got me kinda stumped. A quart in 300 miles is a lot of oil to lose, and as I've often explained "If it's not going out, it's going in". But that should show up as an oil fouled spark plug, which you don't have. How's the coolant look and smell? Any signs of engine oil in it?

 

plenum belly is clean checked that first figuring i must have messed up. changed oil pan gasket as it had a slight leak. now everything is dry and nice. filled up and 500 miles later im out 2.5 quarts just like i was. and th o2 sensor in there might be 3 months old

 

im getting 11 to 12 mpg and coolant looks good. but recently heater blows hot if outside is about freezing and truck is at about 180 degrees but when real cold truck gets 150 and i get luke warm air

 

but that shouldnt drink oil

 

It seems that the oil must be getting into the exhaust stream somehow to clobber an oxygen sensor that quickly. Just to confirm you might pull the thing out to see if it's oily. If so it gives us a direction to look -- if not it leaves a lot more room for head scratching.