It's been a long time since I have posted here mainly because my truck was wearing a bow tie for awhile. But my wife was nice enough to tell me the Bow Tie wearing truck was making a funny noise on New Years Day (seems a small drum corps took up residence in the oil pan). So anyhow now I am back in a real truck . My new to me 1998 F150 5.4 Liter ran fine until yesterday. It started idleing rough and almost stalling at red lights. about halfway home the CEL light came on and is throwing a P0171 code.
So far I have checked for vacuum leaks including all the elbows on the PCV system' tried the spray test with a can of flammable break fluid and a can of starting fluid (man I love the smell of that stuff) could not find a leak. Cleaned the MAF sensor and the K&N air filter (not a fan of these) IAC seems to be working. Only thing I know that is leaking for sure is the driver side exhaust after the cat. But that is the wrong bank if I am correct on which bank is which.
So why only one bank running lean and why does it act like it is only firing on 4 cylinders ? Any help would be greatly appreciated !!

 

A leak at the point you specify would be 2 sensors down stream and too far away from the up stream sensor to cause an issue.
You need to do more diagnostics with a Scanner to get a clearer picture of what's going on.
Look at both banks fuel trims to see what any difference there might be as a lead.
Mass Air meter is common to all cylinders.
Until your able to see or gets some positive lead it just guessing.

Good luck

 

I was thinking the same thing Bluegrass 7 If it was an upstream sensor I would be receiving both a 171 and a 174 so it has to be something related to only the passenger side bank. As I am new to these high tech trucks I don't have a lot of the diagnostic tools. My code reader is just that a reader it doesn't do much more. So I guess what I am looking for is a way to test the items that would only affect one bank of the system. And what those items would be. By the way which highly intelligent engineer decided to move the engine halfway back under the fire wall?!?

 

Look a BOTH LTFT values. It is common for one bank to code out before the other so bank 2 might not be too far behind bank 1.

Your symptoms are of a vacuum leak. The old spray and listen routine rarely works on modern engines, you have to spray and monitor live data with a scan tool to see what's actually going on.

The one who was give the job of cramming everything in there under the hood and still include a crumple zone so you don't get killed as readily in a front-end collision.

 

Does the egr have a tube that ties into the passenger side manifold on 5.4 engines? Some Ford engines are set up this way, and those tubes often break underneath the heat shield sleeve. That could be a source of leakage. At least, that was my experience with a 5.8 a few years ago.

 

projectSHO89 Thanks for your reply as I stated in an earlier post I dont have a scanner that will check those readings. My code reader pretty much just reads codes . My toolbox is full of tools that will fix most anything pre computer guess I am to far behiund the times. Would a plugged fuel filter cause this problem?

BCHauler I am not sure I will have to wait till I get home from work and look.

 

I just went through the 171&174 codes. Turned out to be the PCV tubing. The elbow behind on the intake had a small pinhole. I couldn't find it with stating fluid or anything. I ended up smoke testing it. I made a "smoke machine." I used a new metal paint can. Drilled two holes in the lid hot glued clear 1/2 tuning into the holes. Made one long and one about 16". Threw a rag in there with some hot coals out of the wood burner let it smolder for a bit put lid onto it and hook on end to the brake booster line and slowly blow through the other. Sure enough smoke started coming out rift at that elbow. Cheap easy way to find your vacuum leaks. I think I had 5$ in it. Kinda crude but it worked. Even though the rubber hoses look like they are I'm they can deteriorate and still have tiny pin holes in them. You might try this and see what you find out.

 

Ok I went ahead and changed the fuel filter pressure was 20 psi before the change and 40 after. The gas that did dribble out of the filter looked like hot chocolate totally nasty stuff. this eliminated the 171 code and caused a 443 code. I cleared all the codes and took it for a 20 mile test drive. the engine still has a major miss but none of the codes came back ? any Ideas what might be causing the miss? I started it up and unhooked each injector while it was idling, every injector I unhooked caused a difference in the idle ? maybe they just need a good cleaner run thru them after seeing what came out of the filter ?

 

Did you reset your KAM ? I have seen Ford's do strange things After fixing a fuel trim problem and not doing a reset . Just a thought .

 

Never heard of a KAM what is it and where is it ?

A quick search tells me to pull the 5 amp fuse center row 2 up from the bottom for 20 minutes is this correct ?

 

Keep Alive Memory . Do a hard reset , Might help . Disconnect negative battery cable for a bit . 5 to 15 min. Or use the proper scan tool to do a KAM reset . That sets fuel trims to zero . The computer then starts to relearn . If not done , sometimes , the computer does not relearn quickly enough and gets confused , kind of .

 

Ok will do that and get back with the results THANKS

 

Ok I unhooked the negative cable and let it sit for 20 minutes miss still seems to be there would the lean condition have burned up a spark plug ? as bad as the fuel filter was should I change them anyway ? The previous owner loved JC Whitney but apparently wasnt much on general maintenance

 

A tune up won't hurt , if done properly . But you might save some money by having a proper diagnostics preformed . Many items can cause a miss . You can drive it more and hope it sets a cyl. miss code .

 

Thanks JWC 3 I was thinking maybe some injector cleaner also they cant be fogging correctly with the mud that was running thru them. any recommendations on a good cleaner ?