I Think i have a exhaust manifold leak, loud ticking noise coming from passenger side , trying to narrow it down to manifold. Will a exhaust manifold leak cause a P0171 code. ( lean bank 1 ) . 01 F150 with 117K miles, also MPG seems to be getting worse.

 

You probably have broken exhaust manifold bolts, which is a common problem.

Your 5.4l uses a MAF and O2 sensor system to determine how much fuel it needs and etc. Your manifold leak is probably related to the code.

Get the leak fixed. You will gain mpg and power.

 

I agree, I have seen leaks so small that they couldn't be heard cause lean codes and poor economy. OF course some leaks are hard to hear through all the heat shields found on some vehicles. (Yes, I'm talking to you Nissan)

 

Great , Thanks for the Info . I am pretty sure that is what it is. I hear it could be a difficult job if the bolts break. Do you think should have a Shop do the job or tackle myself. I dont have the tools if a Bolt breaks and I have to retap ?

Any Hints ?

 

Do a search in the V10 Modular section on manifold stud replacement. There are tons of threads in there about replacing studs.

Some studs can be backed out with a vise grip or pliers and some have to be drilled out. A helicoil may even need to be put in. The stud size is M8x1.25.

You may also have a warped exhaust manifold. If you do have a warped manifold I would suggest getting a set of headers

 

Ok Thanks again for the info , I will check it out