I have a 1998 F150 4x4 with the smaller V8 and 209k on it. My check engine light came on, even though my truck still seems to be running well with no problems. I took it to Autozone and they read the codes P0171 (system bank1) and PO174 (System bank2). They said it looked like those codes hit twice and suggested buying some fuel injector cleaner could fix it? So, I bought the $3 STP fuel cleaner (can't hurt right) but I don't think those guys always know what they are talking about, so I thought I'd double check here.... I have no idea what a System Bank even is (I'm not a mechanic). Is this something I should be concerned about? Any suggestions on how I should handle this?

Thanks,
Matt

 

When they say "bank," they're referring to cylinder banks 1 or 2. Bank 1 is the passenger's side and has cylinders 1-4 on it. Bank 2 is the driver's side and has cylinders 5-8 on it.

P0171/0174 indicates that the long term fuel trims have reached a maximum (should be somewhere around 30-35%). Fuel trims are how much fuel the PCM adds or subtracts. 0171/0174 indicates that the engine is running lean, meaning that outside air is getting past the mass air sensor. The O2 sensors see this excess air and the PCM responds by cranking up fuel trims to add more fuel for that more air.

Search this forum using "P0171" and "P0174" as your search criteria. More than likely, you've got a leaking or deteriorated PCV tube connection.

 

First off, don't use the STP brand fuel system cleaner. It will all but destroy the nylon fittings in the fuel delivery system. Need a cleaner- use the Ford recommended Techron. Need to understand the codes- go here:

http://www.obd-codes.com/trouble_codes/ford/index.php
You may need to click on the generic codes at the top of the page. All highlighted codes have further info.

and follow up here:

http://www.motorcraftservice.com/vdi...f/OBDSM601.pdf

This last one is a pdf file and is not modem friendly, suggest DSL or faster or bring lunch as it is 141 pages of manual on your engine.

Have fun!

 

Thanks... I was wondering if there might be an air leak somewhere in the system. I'm not sure if its related or not, but I hear something like an air leak "hisssing" sound when I drive but when I touch the gas pedal or brake pedal it goes away...is this normal or could it be part of the problem?

Thanks!

 

Thanks for the link to the codes, it suggested that the The MAF (Mass Air Flow) Sensor may be dirty or faulty. Are those easy to check? Where is it located?

 

It'll be somewhere between your air cleaner and intake manifold.

It could be the MAF sensor but I tend to agree with the other guy that said air is probably leaking in somehow. There could be a leak somewhere between the MAF and the intake. Could be a loose hose, bad connection, leaky gasket, etc. Sometimes if you idle the engine and then spray some carb cleaner (carefully) around some of the likely spots you can hear a change in tone from the engine. This could tell you where the leak is.

 

Thanks, I'll try that.

 

Interesting you've got the same computer codes and sounds like you have the same "hissing" sound I do. Just curious is your truck jumpy at the 1500-1700 RPM range?

Let me know if you find your problem I've been looking all over for mine!

 

Does your hissing sound go away when you hit your brake pedal and/or gas pedal? I can't figure it out either Please let me know if you figure it out, and I'll do the same for you if I figure it out... Matt

 

Yes.. Seems like breaking/gas changes the whine.

Going to rip up my truck this weekend and clean out the intake and crap and I'm going to check all the sensors and crap while I'm at it..

 

[QUOTE][Search this forum using "P0171" and "P0174" as your search criteria. More than likely, you've got a leaking or deteriorated PCV tube connection./QUOTE]

I've got $10 on quintin that says he's right on the $.

One trick the mechanics I know use to find a small leak in the pcv system is to spray break cleaner on the suspected areas with the motor running. The break cleaner will enter the system through the leak and cause the engine to increase rpms. It's not a huge increase but it is definately noticable. This may save you lots of time. I'll bet it's the notorious rubber elbow. Not sure where it is on the 4.6. On my 4.2 I fixed it for $4.00 and in 2 minutes, and thats including the time to wash my hands afterwards.

 

[QUOTE=pops]Which elbow are you refering to? got a pic?

Next weekend a friend (ford mechanic) is going to go over the truck for me.. our scheduals conflict too much to get it looked at sooner by him.. too many odd quirks with these f150's lol.

 

mscruton& bcshepard,

I will speak or rather write plainly. I don't mean to insult you or (God forbid) effect your self esteem!

You have a VACUUM LEAK! Everything you have written points to it. You both have gotten good advice on this thread. Forget about the sensors. They are working fine. That is why you're getting the CEL.

Just find the leak and plug it. Listen to it and try to figure where it's coming from. Get the general area of the "hiss" then pinpoint it using the carb cleaner as mentioned.

Let us know where you find the leak and how you stopped it.

Good Luck

 

I just fixed a problem with the same codes. It was 2 elbows that were melted and sucking air. one of the elbows was on the back side of the intake. The other is under the IAC, this one is hard to see.
Email me and I will send you some photo's.

 

Mine was air leaking by the intake manifold to heads gaskets. i retorqued the bolts with the engine cold and problem is gone.