roara

Hey guys, need some helpful hints on the rough idle issue please.

2004 4.6, company truck with 320,000. Just as tabs were due and my employer was about to sign over the truck to me, I get a CEL.

Codes P0171, P0174, scanned at Autozone.
Lean condition bank #1 and #2.

Fuel pressure issue or MAF sensor.

Starts fine but after a few minutes the idle is chugging and sometimes wants to die. Drives fine until you get in to stop and go traffic or at a light.

I have a HF fuel pressure gage and it reads 35-39 engine running. Seems ok from what I've gathered.

Replaced fuel filter, no change.
Sprayed MAF, no change.
Replaced MAF, no change.

FPR?
My experience with a bad FPR was hards starts after warm. This is not the case here.

I have a 20 day temp sticker with 7 days left, you only get one in Oregon per year, I think.

Any similar problems with useful ideas would be greatly appreciated!

thx, Mike

1997F1504x4

I have the same problem with my 5.4 im curious to see what it is

roara

Did I post this in the wrong section? Should I head for all years mechanical? I figured the 04-08 was best for my need for help.

Nobody reading has had this problem?

MHOWELL34

Clean your throttle body guys! Go to Advanced get some MAF Cleaner and Deep Creep for that throttle body! Mine did the same and would even die if you played with the pedal at low rpm and rough idle. Had oil caked on the bottom of it and around the rim! Runs like a champ now!

Also try 5w30 thats what i'm running since im over 200k now. Does it have the Gott's mod? Could give that a whirl and see if itll make the MAF give you more gas to not be on lean side.

Mad Irishman

^^^^^^^^
What he said.

uzikaduzi

I think cleaning the TB is just general good maintenance but if you're getting lean codes, you don't want to increase airflow... in fact lean conditions can be caused by increasing air flow with CAI's or even the Gott's mod... i would check the intake (starting at the filter) for leaks... if you don't get a seal on the air filter, it can suck too much air and throw lean codes

1997F1504x4

As for me I already cleaned my MAF and made sure to use MAF cleaner and I replaced the seal around the airbox tray as well so all that is good. I am also running 5w30 motorcraft oil as well. I haven't had the lean code pop on in a while but it will randomly go into a rough idle or rarely stall while sitting in park or at a light

uzikaduzi

was the seal around the air box in rough shape? I've heard/seen that throw lean codes with a few different cars

lewissa81

When you cleaned the TB, did you replace the TB seal?

MHOWELL34

Nope, bolt it back on and truck on