Hi All! I have need of help with 2 questions regarding our 2001 F150 Supercrew. My 2 questions are:

#1) My 2001 Ford F150 Supercrew (5.4L, 230,000 miles)has the check engine light on with the code reader telling me that it is the P0174. The truck would run rough when cold (usually in the mornings) and sometimes it would get close to stalling out when coming to a stop light. So we would quickly put it in park and give it some gas to rev it up a bit. After the truck gets warmed up, it runs great with no hint of the rough idle. Since this all started I have changed out the PCV valve and replaced the PCV hose (including the elbow). I have also replaced the Idle Air Control unit but that didn't really make a difference. We then experienced a cylinder #4 misfire which we resolved by changing out the cop with a new Motorcraft unit. The misfire went away but we still had the problem of running rough at idle to the point of stalling out at stops when the engine is cold. A few weeks ago we cleaned the MAF sensor and that seemed to help. The truck doesn't run as rough now (when cold) at stop-lights, but occasionally it will still have the loping idle. We cleared the check engine code and it stayed off for about a week before returning.

I don't know what else to check other than trying to see if there is some type of vacuum leak, but I don't have access to a smoke machine nor would I know how or where to hook one up. Does anyone know if removing and cleaning the throttle body would help? Any ideas of what could be causing the trouble, or what I should do to further isolate or troubleshoot the problem? I saw a you-tube video on the F150 intake manifold gasket possibly being the problem and although I hope that isn't the trouble with my truck, if it is then I will have to deal with it. We need the truck to get to work and the car is now due for a registration renewal, but we can't get a California smog certificate with the check engine light on.


#2) We had some heavy rain in January and February and as usual water got into the truck from somewhere by the back window. From watching some you-tube videos I am reasonably sure the leak is from the 3rd brake light above our back window. However, where I really need help is with the horn and alarm. After a few days of heavy rain, we noticed the horn wouldn't squawk when we set the alarm. Instead it was a muffled sound. And now the horn doesn't work at all. I figured it just got wet and would start to work again when it dried out but it's been a few months and neither the alarm nor the horn work. Any ideas on what to check or what could be the problem?

Any and all help and advice is appreciated and let me say thanks in advance to all who can offer any suggestions.

 

Nothing like starting with the easy parts first.
After you find the horns, where they hid them, a simple check with a test lite to the wire that splits between the two horns, should confirm if power is getting to the horns.
Once that's done , I have removed the horns and some have a serrated top screw that you may be able to turn a little in each direction. then try applying power to the horn and sometimes they will start working again. If no power is getting to the horns, work your way back to the horn relay. Also if the problem is with the horns themselves , you should hear the relay clicking when you depress the horn pad.
Have had success with that procedure several times in the past.
TIP; stuff a rag into the horn when you are ready to check it, they can get pretty loud !

 

Thanks for the help. I will probably concentrate on the P0174 code first and I am sure I will need to get an evap smoke tester to help find the vacuum leak. Any suggestions on this would also be helpful!

 

Unplugging the IAC on cold/hot idle has no change?

Rather than smoking, you might try some TB cleaner etc sprayed at the intake mating areas cold and see if a bleed is detected..