Hello! I'm new to the forum but have been reading threads for info for quite a while. That being said, and after having read similar threads about this, i am having problems tracking down the root cause of these codes. I have replaced several parts and checked for vacuum leaks, but my short term fuel trims are still elevated at idle. And not all the time, just sometimes. Replaced: maf sensor, fuel filter, downstream 02 sensors (not related but found out they were bad), several vacuum hoses, etc. Any new ideas about these pesky codes?

 

Do you own a truck?

Those are the most common codes that come up. Doesn't look like you've done much to track down the problem. Specially with all the info there is on them here.

 

2002 F150 5.4L K&N CAI. I have repaired a vacuum leak and sprayed starter fluid all around intake hoses and gasket, no jump in rpm. Also tried using water while engine running at the intake manifold gasket to no effect. I found some dry rotted hoses that i have replaced but it hasn't changed anything. Upstream 02 sensors are reading normal. Short term fuel trim at idle bank 1 and 2 running around 20-30 which is obviously way high. After replacing maf with a known good one, problem went away for a day (short term fuel trims around 0.0 at idle) then returned. Fuel pressure at idle is about 28/29. Not sure where else to go from here. Pcv elbows are good.

 

For clarification, i have also repeatedly cleaned maf sensor wire with electronics cleaner and have never over-oiled filter.

 

When spraying and checking for vacuum leaks you need to be hooked to a scanner that shows live data keep an eye on the fuel trims.

 

I'm using a foxwell nt301 scanner. What should I be looking for the fuel trims to do while spraying? Sorry, im asking because I dont know. I've only heard of monitoring rpms for an increase if starter fluid gets into intake.

 

I wouldn't use starter fluid, since that will compromise the vac line seal. Use propane for leak testing.

That K&N is poison which WILL screw up the MAF quickly among other things. It will eventually kill the engine, shorten the life of drastically. The air intake probably isn't sealing totally. What you can do is keep the K&N tube, trash everything else and adapt the factory air box to it and most importantly, run a good dry element...like say a WIX filter. Otherwise you can forget about getting rid of those DTC's.

How's the MAF oring, does it have one installed ? Make sure it's there.

 

Jbrew, thanks for the feedback. I kept all the original intake just in case I had problems like this. I will look into WIX filter. I will have to double check to see if maf has an o-ring. Is there supposed to be one where the senator's flat piece screws on or is there one where the tube portion inserts into air flow?

 

Senator ? lol. It's inside the MAF. It's a 7/16 o-ring. They are easy to loose.

I use a Volant tube, but K&N tubes can be incorporated. You can mod the factory air box. Here's a link of the set up, -

https://www.f150forum.com/f6/engine-...9/#post4628445

 

Thanks for the help. Sensor is what I meant lol. Autocorrect