Have been getting codes P0171 and P0174 (too lean on bank 1 and 2) on my 98 F-250 Ld, 5.4. Have visually checked all the vacuum hoses I can see,
and the elbows on both sides of the PCV tube and they all seem o. k. PCV
also has good suction. Used a K&N air filter for a few months 2 years ago then went back to paper. Removed the MAF sensor today and it looks clean inside and out. Am wondering if spraying the MAF with electrical cleaner will do it any good or is that only usefull if it's super filthy inside?? The truck has 80K miles on it and runs as good as it ever did, but now displays the CEL.

 

You can try spraying the MAF sensor, but be sure to use a contact cleaner that leaves no residue.
Just for you general info, I spent the last 2 mos chasing the same codes on my wifes Sable. I cleaned then replaced the MAF, replaced fuel filter, new intake and plenum gasket set and checked everything for a vacuum leak with no luck. I finally gave up and took it to the stealership. He replaced the PCM (powertrain control module) for about $400 and its been fine for about 3wks.

Good Luck

 

unplug ur maf and clean it...

 

MAF didn't look dirty in the least but removed it and sprayed a very light amount of carb cleaner on the 2 wires. Let it dry then replaced it. Decided to put in a new PVC and new rubber grommet even though suction felt strong through the old PVC. While taking out the old PVC I noticed it pulled out from the grommet with not a lot of resistance. Although there was no side play, it sure slid out easy. With the new rubber grommet in place the new PCV took some pushing and shoving to get it seated all the way in, and is a super snug fit. Although small, am thinking this MIGHT have been a potential leak point leaking just enough to cause the lean condition CEL!?! The codes are cleared and the fingers are crossed, and I guess we'll know in a few days if we found the cure. Thanks for the comments.

 

yeh that should fix ur problem

 

Could be that there is a buildup of the oil on the MAF from the K&N filter that you used. I had my truck dynoed this weekend and on the first 3 runs the hp was about the same but on the 4th run I cleaned just my MAF and got 8 more rwhp. So it could be the oil buildup on the wires in the sensor. Not sure but it worked for me.

 

the Maf sensor reads air volume by the rate at which the sensors are cooled. the MAF sensor is heated to 200C and the passing air cools it and the cooling motion varies resistance thus tellin the computer how much air is flowing.

 

I stopped using the K & N because of reports that it let in more silica (dirt) particles than the standard paper air filter. Did read later that a few people reported oil from the K & N getting on the MAF sensor. On mine, the throat of the MAF looked and felt oil free but thought it wouldn"t hurt to clean it anyway. Cleaned the MAF before reading jr105's comments. If I need to clean it again I'll try the electrical contact cleaner instead of standard carb cleaner.

 

I have replaced the air intake hose twice on my F150, still get the lean code. Took it to a dealership and they wanted $400 to replace air intake and plenum gaskets. Questions - how difficult is it to replace these, how much are the parts, and any suggestions on how to know whether or not it's the gaskets or the PCM? Thanks.

 

The plenum and intake gaskets are not easy to change, at least they weren't on my wife's Sable. Lots of stuff to go through to get to them. I went that route because of a tsb that is out on the sable 3.0 duratech engine. Usually if you have a vacuum leak that is bad enough you will see a rough idle. An old way to find the leak is to use an UNLIT propane torch. With the engine running open the valve and point the nozzle at the suspected leak. If the propane gets sucked in the idle will pick up.

The gasket set I bought was about $35. It's a very labor intensive job.

 

Update a week later: Although the engine never ceased to run and idle well, the CEL showed a lean condition code on the 5.4 engine. After spraying cleaner in the MAF (although it looked clean and dry) and replacing the PCV and rubber grommet, all is well and the smog test is passed! I believe replacing the rubber grommet was the big thing. The old PCV was a little too easy to slide out of the old grommet although this was only slightly noticeable. There must have been just enough micro leakage to put me borderline lean.

 

Nope - that would be Air Mass, not volume. Big difference - The former accounts for changes in density, the latter does not.

Volume is a useless measure for oxygen content, if you don't also know the density. - that would be physics 101.

Gee - hence the name, I guess - M*** AirFlow sensor.

And another Nope - that thin filament is kept at a constant temperature - the variance in current necessary to keep it at a constant temperature while the airflow is attempting to change it, is what the PCM is sampling - that would be electronics 101: E=IxR

Whut da hek dey teechin' u in dat skool, Slower ????

Nice to see you being helpful - I'm just trying to make it accurate.

Cheers
Grog