2003 5.4 if oxygen sensors are bad would it cause a truck to miss, got 4 oxygen sensor codes, truck misses from about 60-70 every now and then, if the fuel pumps weak wouldnt it be sluggish ALL the time,

ran the codes and nothing but the 4 02 sensor codes, how can we tell if theres no code!

 

i just wanted to make sure everyone knew what the codes were.

quick question what rpm or gear is the truck in when it misfires at 60-70mph? is it at wot?
a weak fuel pump generally shows up at higher rpms when the pump isnt supplying the fuel that the engine requires. a bad fuel pump feels almost exactly like a partially clogged cat. o2 sensors wont necessarily cause misfires but when it sends a signal to the pcm and the pcm changes the a/f mixture then it can sometimes feel like a misfire.

 

4th gear (automatic transmission) and about 1800 rpms,,,, not WOT because we were WOT'ing all day sunday and it wouldnt miss until we were cruising at about 70mph, and it only misses sometimes,

well i say miss, it feels like its missing, some guy at ford said it was the transmission slipping and made it feel like its missing, but thats a load of bs cuz hes had the filter and fluid changed 2x now and doesnt rag on it

 

how old are the plugs? and coils? and what brand plugs? was dielectric grease used? have you cleaned the maf yet?

 

plugs are about 2k miles old, coils are original, motorcraft plugs what else!!!! grease was used (i didnt use it on mine and mine runs fine!) and no i have not

 

you work at a quick lube right? you guys got a air nozzle? i would pull the coils and blow out the plug bores and make sure there is no water down in any of them.

 

good idea, but why would it only miss at certain speed/RPM cuz in my truck i had water in the 7th cylinder and it missed as soon as i started it till i got the water out

 

and wouldnt it show a random missfire code, or a misfire with a certain cylinder?????

 

there is a bigger load on the engine in o/d. i personally think its a cop failing because of the mileage and the issue your having.

low grade misfires are a pita, they dont always like to throw codes.

if you can find someone with a scanner that can pick up misfire data then i would have them drive it with the scanner hooked up. it'll make things much easier since it wont throw a misfire code. that or just start replacing the coils.

 

thats what my daddy was sayin, so i guess what i could do is take the coils off mine and put them on his, and see if it runs better, good thing about having the same truck !

 

ok so we went and got diagnostics ran on his truck, he said the truck isnt getting enought fuel, that would be fuel pump probably eh

 

was the pressure checked to verify not enough fuel? if so then its most likely the pump, thats why the filters need to be changed no longer than every 20000 miles.

 

idk he ran a computer diagnostic on it, i still need to get one of those pressure checkers

and yea i had to change my buddies fuel pump on his tahoe one day because it wasnt ever changed at about 130k, then he changed it and the truck wouldnt start

 

Is this the truck that still had the original fuel filter with over 100k on it?

 

YEP!