leatherneck123

Hello everyone, I recently purchased a used 1999 Ford F-150 V6 4.2L. This is my first truck ever. I really enjoy driving it so far. However, when I purchased it from a guy on Craigslist he told me the engine light was in because it needed a tune up. I figured because it ran a little rough, he could be right. So, I went out and purchased new spark plugs, and a fuel filter. I also changed the oil so I would have a fresh start with this new toy.

Low and behold, the engine light is still on. I'd like to think that I can usually figure out most of the easy to medium things on my cars when I have a little help.

So that's what I'm hoping for on this forum. A little help. Below are the listings of the codes that come up. Please let me know what you would do? What would be the first thing, or most important? How would you narrow down the exact problem. Any help is appreciated. Thanks.

P0340 Camshaft position (Bank 1 or single sensor)

P0401 exhaust gas recirculation flow insufficient detected

P1131 Lack of heated oxygen sensor (Bank 1, Sensor 1, switch indicates lean

P0171. System too lean

P0174 System too lean

Sappy72

Not sure about your 4.2 since I'm running the 4.6 but when I got hit with the last 2 codes you listed, it turned out I had a exhaust leak right at my manifold.
You're reading too much air in the exhaust causing a lean code. Is it too much air or not enough fuel, someone more knowledgable will have to help clarify that for you.
Maybe a faulty O2 sensor too.

Hope you get it figured out.

leatherneck123

Thanks for the response. I think I'll replace the O2 sensor to start.

leatherneck123

Anyone else?

DaytonLax14

I'd also be curious about what people say about the last two codes you mentioned as well because I've got the same codes. Already replaced the iac valve and cleaned the maf sensor but still have the codes.

akdoggie

4.2 engine showing P0401 is EGR with probably a clogged up port. You may have to clean the port out to get the 401 to go away. P0171 and P0174 are lean air codes dealing with a vacuum leak or dirty MAF sensor in the air tube. Clean this with electronic cleaner ONLY. Other items mess up this sensor. P0340 is most likely a malfunctioning cam sensor. Lastly P1131. This is usually a bad 02 sensor or bad wiring to the sensor. Before buying a new sensor, change it with the opposite bank sensor, clear the codes and see if it resets or goes to another number. If it switches to another P113= number, then the sensor is faulty and needs replaced.

Hope that help you out some. Good luck. Don't forget to check the PCV and if you change it, use a Motorcraft PCV. Check the fuel filter also, as it can also set a lean code, when enough fuel doesn't get to the rail.

leatherneck123

Outstanding, clear response. Looks like I have some work ahead of me. Thank you very much!

UtahGuy

And just in case it needs to be said, next time check those engine codes before you buy the truck.

leatherneck123

leatherneck123

Ok. So I replaced the camshaft and the sensor. That wasn't as bad as trying to put back the water bypass pipe. That thing was a pain in the rear. Put it back together several times only to have it leak. Ended up using threading tape in order to not have a leak.
Also cleaned the EGR ports on the bottom half manifold. However, I still have the same codes. I figure I should replace the egr valve and the egr pressure sensor. Any recommendations are appreciated. Thanks