hey, I have a 2001 f150 5.4L v8
On cold mornings (under 45 degrees or so) my truck has a bouncy idle when stopped at a light or stop sign. it starts fine and once it warms up it runs fine. It is throwing po171 and po174 codes and I have replaced old hoses and do not believe it to be a vacuum leak. I have not done anything with the maf, but that is my next step once i get time to do so. I have looked up videos and forums and anything i could find on the subject and thats all I can find. anything else anyone can think of that it might be would be greatly appreciated.

 

It's a vacuum leak.

Probably manifold gaskets, cracked manifold, vacuum line, or something along that line.

 

Ok, is there a way to check that before I tear all that apart, or do I just need to replace it and hope for the best?

 

"hoping for the best" will be one huge waste of time and money---unless you have plenty of both have those leaks diagnosed first.

If you've checked and are 100% certain the PCV plumbing running to the back bottom of the throttle body is intact then begin checking for leaks with the "spray method". Videos of this process can probably also be found online, search for something like "finding engine vacuum leaks...." or something similar. (That phrase should be generic enough to get a lot of results---wade through them for the one that suits you.

 

Yes. A scan tool that can display live data (STFT or upstream O2 voltage) plus a spray can of brake cleaner, carb cleaner, starting fluid, etc. Observe safety concerns, you'll be spraying a flammable on a running engine so stay ventilated and keep an extinguisher handy.

Simply spraying and listening rarely works unless you have a severe leak that is causing a pronounced impairment of idle quality (loping, stumbling, etc).

 

sweet, thanks guys

 

My 2007 f150 every now and again gets rough idle and eventually kicks itself into limp mode. I found that my throttle body gets a bit dirty along with maf. I just pull it apart clean it well with cleaners and put it back together. Works good for a few years. Might be worth something checking out.

 

Your 07 is fairly different than an 01. The throttle control is COMPLETELY different.