Can anyone please suggest a model of a scan tool that will read fuel trims for my 1997 ford f150, 5.4l. i have been having trouble with the engine running rough for awhile now and it just seems to be getting worse no matter what i replace on it. i cannot find any vacuum leaks and have changed just about every electrical part on the top of the engine. thanks, Brad.

 

Do you think you could tell us just what kind of problem you are having and what have you done/replaced so far. Running rough, when,,, is it misfiring, engine speed going up & down ?

 

it runs rough after warming up and stalls when i come to a stop. it has a code that says it has a vacuum leak but i cannot seem to find any leaks. i have replaced the EGR valve, the IPS, the PVC valve and teh DPFE. I just had the cats replaced on the drivers side. someone said something about checking the fuel trims and if they are more then 10 percent off then it means that there surely is a vacuum leak.

 

I don't know of any cheap scan tool that will give you fuel trim info. The ones that I know of cost in the area of $3500 and up. Maybe someone else can provide better info on that.
Since you have a code indicating a vacuum leak and the symptoms of a vacuum leak you are 2/3 of the way there. Sometimes a can of spray carb and choke cleaner sprayed in suspected areas will help pinpoint a vacuum leak by changing the idle speed when the leaking area is sprayed.

 

here is something i have been thinking about. when i had the cats on the drivers side replaced the tech told me that the passenger side would need to be replaced in the near future. i know that if there is a hole in the cat it will sometimes throw a code showing that the o2 sensor is bad. could the O2 sensor cause a code that shows the engine either has a vacuum leak or is running too lean?

 

Well, you can put this to rest if you go to Autozone and get the codes read for free. If you report the numbers back to us idiots, we'll put our heads together and I'm sure we can give you the proper diagnostic direction.

 

That is the one field I was told where I attained perfection.
They told me I was a perfect idiot.

 

the codes were p0171 and p0174

 

Since you have codes indicating a lean condition on both banks, I would suspect it is something that is common to both banks ,possibly like an intake manifold gasket or throttle body problem. Did you get a chance to carefully check all the vacuum hoses for cracks /splits or loose connection?

 

i have checked and rechecked all vacuum lines and even replaced the gasket on the throttle body. not sure how to check the intake manifold gasket without taking it off. starting to think i may be better off taking it to a shop and letting someone else figure it out, but don't want to spend the money and have it turn out to be something simple that i just overlooked. any suggestions on how to check the intake manifold gasket?