i just bought a 96 f150 supercab with the 5.8 and the code its showing is that its running lean. so im guessing a gasket, are any of the intake gaskets a normal problem on these or im i looking in the wrong place. i tried spraying the intake and vacuum lines with carb cleaner but didnt notice any problem areas. any help would be great

 

Yeah it would seem as if you are getting some unmetered air in there. Probably your upper intake gasket but also check the throttle body and hey, clean your MAF with some MAF cleaner.

 

also check your fuel pressure. might pull a couple plugs to see how they look as well.

 

Are you sure the O2 sensor is working right? Its what actually determines weather the engine in lean or rich.

Also are you down on power?

 

great power, ****ty mileage. ok thanx i will try checking them things

 

also what shud the fuel pressure be

 

fuel pressure should be 38-42psi both with key on engine off and with engine running.

you might also pull the vacum line from the fuel pressure regulator and see if any gas comes out of the vacume line. if so then the FPR is bad and needs replaced.

you still have all 3 o2 sensors in place and cat converts correct?

 

Exactly what code number do you get? I suspect the correct code definition for it is probably something like "at lean adaptive limit" which means the engine is running rich.. which makes more sense given the bad fuel milage, and if that's the case you should be looking for high fuel pressure or a leaking FPR, a flooded evaporative system caused by bad check valves in one or both tanks sending units, or dead O2 sensors... though there would be additional codes for that.

 

as far as the exhaust its all factory correct. but the book only chows i shud have one o2 sensor. i believe i have a vacuum issue because when i have my vent on and i step into the gas more it changes to defrost and i had the same prob on a dodge and it was a vacuum issue. im going to check the fuel regulator and pressure now. thanx for the help

 

well your first post says your asking about a 96 in which case would be obd-II and would have 3 o2 sensors.

if you just mistyped and meant 95 then yes you would only have 1 o2 sensor.

 

Wasn't the 96's MAF (5.0 and 5.8) also?

 

i was wrong i looked at the book again i do have 3 O2 sensors and yes its the obd-II. the parts store that checked it for me said that it said running lean. my fuel pressure is rite at 39psi and my fpr isnt leaking. how do i check the flooded evap system. ive looked everywhere and not finding a vacuum leak anywhere

 

Is your truck have a MAF or MAP sensor? It could be messing up, cause the air/fuel ratio to be screwed up.

 

pull codes yourself. you need to perform KOEO and KOER.

crawl under your truck and make sure each o2 sensor is connected. depending on the mileage of the rig they may need replaced.

pull some plugs and see how they look, will help identify which area could be having the issue.

 

Non functioning EGR will cause a lean condition also.