Hey all! This is an awesome board!
I just wanted to run the 171/174 Code problem I am having past everyone. My wife's '98 F150 with the 5.4 recently kicked on the CEL again with the 171/174 codes. I replaced the MAF, DPFE sensor, IAC motor, did the PCV hoses fix, and cleared the CEL only to have it kick on again two days later (around 35 miles of driving). Same 171/174 codes, but the truck runs fine, with no RPM hunting or stumbling. I have noticed a very slight ping on acceleration, but I can barely hear it. I don't think it's the O2 sensors, but I'm about to change them as well. The odd part that we noticed about the CEL coming is that every time it comes on, it's when making a right turn! Odd coincidence! The truck has 125,000 miles on it, and has been great, even with the light coming on! ANY help would be appreciated! Thanks in advance.

Matt

 

Re check the hoses - Check -clean your new MAF , it may have something on it - Did you reset the PCM ? I would also unhook the batterey for 20 minutes , let it go threw a full reset - 20 minutes at least.

Clean your throttle body (inside - all ports - they can get clogged)

If you do all that and the same prob - your intake gaskets are prolly leaking.

Good Luck

 

I reset the code using a scanner/code clearer that I purchased from an O'reily's Auto Parts store.

Do I need to remove the throttle body, or can I clean it on the truck?

If the intake gaskets were leaking, or a hose for that matter, wouldn't it be hunting for idle, or running weird?

Thanks for the help!

Matt

 

I would disconnect the battery - it's not exactly the same as an erase from the scanner , that will prolly fix the problem for yuh. Start there anyway, it reboots your PCM.

I was talk about removing the throttle body and manually cleaning - you can purchase automotive pipe cleaners at an auto supply for the job.

A few people and me as well polish the TB and TB elbow- Smooths things up a little more all around , it's not nessesary though.

 

I suspect an air leak somewhere. With 125,000 miles it wouldn't be suprising to have a bad gasket.

 

Okay, I'll disconnect the battery tomorrow when my wife gets home from work. If that doesn't fix it, I'll pull the throttle body and clean it. I have some carb cleaner, and I think I have some pipe cleaners. If not, that's just a trip to the parts store for more stuff! Can't have enough stuff!! I'll post after the work is done! Thanks guys!

Matt

 

I would suspect a vacuum leak that effects both cylinder banks wpuld not be gasket, but more like a hose leak. check th pcv hose at th back of the intake/throttle body it is real common for them to collapse, especiially with that mileage.

 

Yes - thats the first place you would go for those codes and the MAP - jump back - he replaced all that already, but that's usally what it is, you guys are right..

 

Reset the KAM by disconnecting the negative battery cable and touching it to the positive terminal, then retest.

 

sorry to hijack this thread but I threw the same codes 174 and 171 this weekend on my 99 5.4L F150. I only get a service engine soon light no CEL. I drove the truck 100 miles with light on and the truck doesnt seem to run any worse, only thing I did notice is a very slight rough idle....should I check the PCV and connections?

 

Okay, you got me here. What is the 'KAM', and isn't touching the ground cable to positive going to short something?

Matt

 

KAM is short for Keep Alive Memory. This is the PCM's short term memory of sorts, stores things like idle data, fuel trims, trans tables, etc. It's a good idea to reset the KAM whenever you fix something engine or trans related, so the PCM will go into adaptive strategy and relearn to your latest repairs.

And no, touching the negative battery cable to the positive post won't result in sparks or fire. It'll just forcibly clear the PCM's memory.

 

I will try resetting the KAM and see what happens!

Matt

 

This may be a silly question,but what kind air filter do you have in your truck? and i would check your lines riunnig to the vacumn module on your front diff as well. There could be a leak there too.

 

Stock airfilter that I modified the housing (cut away some of the material around the filter to get more airflow). I did that about 4 or so years ago, so I don't think (hope!) that that could be the problem after this long.

Matt