P0173 Fuel Trim Malfunction (Bank 2)

[99 galant]

Would this litterally mean there is something wrong with my seal around the gas cap?

[jermyjerm]

On V6 engines,this code refers to the fuel trim functon for the rear cylinder head.(the term"fuel trim" refers to the response of the volume air flow sensor,the fuel injectors,the fuel pressure,the engine coolant temperature sensor,the intake air temperature sensor,the barometric pressure sensor and the oxygen sensor to intake air leaks or cracks in the exhaust manifold.)I am quoting the Hayne's manual word-for-word here,wish I could narrow it down for you,but in my mind,the gas cap leak would throw a evap leak code also,and doesn't seem like a root cause for your troubles.Never a bad idea to check that seal though.A crack in the exhaust mani would seem easiest to detect,as it would be audible and air could be felt putting through said crack with each exhaust pulse.Intake leak not always so obvious,maybe listen for hissing or search through the I4 intake leak posts on the forum for ways to diagnose such a leak.

[jermyjerm]

Ha!I just NOW figured out why you think it would be the gas cap seal!"fuel trim"is definetely not the trim around the fuel cap!Thanks,not to be an a-hole,but I haven't laughed like that in a while!

[99 galant]

I also have never had to worry about any engine codes before. I wonder if the seal on my valve cover is bad because the shop did a shady job on it. It was "bent" and they just put some crap in to fill in the space instead of putting a new one on. Would that have an effect at all?

[jermyjerm]

No.Short version of what I said before-all those sensors are "talking" to each other to supply the engine with a stoichometric air/fuel ratio.Mass air sensor says "x" amount of air is incoming,fuel injectors supply appropriate amount of fuel,then o2 sensor sniffs how that combo is burning.The other sensors I mentioned are critical too,and are helping verify air/fuel needs.The problem arises from the o2 sensor saying "wait,we worked hard on this air/fuel ratio but is still too lean".This is most likely from an air leak either in the exhaust mani or intake mani.Basically,unmetered air is making its way either into the combustion chamber or exhaust and the o2 sensor is pissed.The o2 sensor itself may be malfunctioning and unable to accurately "sniff"the exhaust,but im not convinced of that.Most times,the o2 sensor acts up when it is left in too long and becomes clogged in which case,it would definetely not sense too much air.Ok,maybe this was the very long version.I hope this is helpful.