Got a new to me truck (5.4 with 95,000 miles) couple months ago and have replaced all the fluids, plugs, air filter, fuel filter, cleaned maf sensor and throttle body. All tires at correct psi.

Idle is somewhat rough. Not too bad. Stays at around 600-675 at idle.

I am getting 9-10 mpg around city

I think I might be running rich. I have no codes but I do have all the values for the engine.

Short term fuel % - bank 1 = -0.7
Long term fuel % - bank 1 = 3.18
Short term fuel % - bank 2 = -0.5
Long term fuel % - bank 2 = 5.12

My fuel rail psi is 39

If I need to post anything else then let me know.

Could it be my injectors stuck open? I would think that would throw a code but guess not?


I've done some research and am at a dead end

 

what year ?

 

Positive numbers indicate that the computer is adding fuel. You may have a vacuum leak; do the fuel trim numbers get closer to zero at higher RPM?

 

2005


I know they get higher, I will check in the AM to see exactly.

 

What size tire are you running? Are those fuel readings at running temp or warming up? Do you have a CAI or factory intake? If you have a K&N CAI and it's cold outside that would cause ya to run rich. Do you know if or when the plugs and COP were replaced?

 

I am running 275/70/18 bfg all terrain ko and I have the stock air filter. Readings are after being warmed up. Were replaced roughly 5 months ago, somewhere around there

 

"I am getting 9-10 mpg around city".

Sad to say, that's about normal for these engines/trucks in city traffic. Idling and accelerating is not their forte. Most will get from 16 to 20 on the highway if kept under 65 mph.

 

I'm headed out to the ranch today, so I will see what it gets on the highway. I just feel like it may be running rich. Is there anyway to tell by looking at the exhaust pipe? I can upload a pic if need be