The light has been on for about six months now. The truck seems to be driving well, with no problems. I disconnected the battery and reset, but the check engine light came on in a few days. I've done this several times, but now it comes on much quicker. I finally got a hold of a hand held OBD and the codes are 171 and 174, which indicates bank 1 and 2 being to lean. I since have removed all four 02 sensors in the exhaust to find them to look good. I then removed my K&N air filter and replaced with stock version, and attempted to find vacuum leaks in engine compartment. No luck. Like I said the engine runs and sounds good, its just the check engine light is driving me crazy. Can someone steer me in the right direction on this matter, with out going broke? Thanks for your time if you reply.

 

After changing the air filter and cleaning the 02 sensors and the MFS, the light did turn off after resetting again, and it seemed to idle better, but then one day later the light returned. Had my Pop look at it (retired GM worker) and he said he could hear a vacuum leak maybe. I sprayed everywhere, but can't find it.

 

Have you tried changing your fuel filter?

 

Not yet.....I have 103,000 on her....I will change and post what happened...Hopefully I will not catch the garage on fire. Bye

 

Haha. Just keep a big towel handy to catch what little gas comes out.

I'd bet 5 bucks the problem is your fuel filter.

 

A P0171 & P0174 code at the same time almost always points to a vacuum leak. Better listen to the Old Man.... he knows what he's talking about.

Anyone know if Ford used the same crappy material in the PCV hose elbows on the 4.2 as they did on the V8s? If so, that's the first thing to check.

It ain't the O2 sensors. A dirty MAF might cause this combo, but the vacuum leak is far more likely.

Steve

 

Just got back from auto store, first goin change fuel filter, and check that PCV valve location again. Thanks Steve. I'll post what happens.

 

Put a new fuel filter on today and checked again for vaccum leaks. During this time a disconnected battery to reset computer so the check engine light would disappear. Haven't had time to drive it, due to watch the kid. I'll check her tonight when I go into work. Post findings later.

FYI, I did check/clean the MAF sensor a week ago.

 

Well after 20 miles, the CHECK ENGINE LIGHT came on again,,,,,,UGH!!! Back to the drawing board. I did noticed that after replacing the fuel filter it did idle better again. Once check engine light came on could tell no change in performance. Again my Pop said that the computer would compensate to problem with what evers going on and the truck should run properly. I guess now the next thing is to really check good for vacuum leaks.

 

Had same type of problem. I found hard plastic vac. lines were damaged. The were located behind the battery. Replaced with rubber hose. Problem solved. Hope this helps.

 

If you've still got access to a scan tool, what's the freeze frame data look like for the 171/174 (if you got that capability)? BARO? Long and short term fuel trims? For some reason I remember something about intake manifold gasket leaks on the 4.2s or a leaking PCV tube or something.

 

No don't have a code reader, I'll have to take it to auto store. Can they tell me what these freeze frame codes are with the one that they use. The one my Dad had was a cheap version that only showed the 171 and 174. Also when I was checking for vac leaks, I think I can hear a sucking sound when I shut the motor off. Its coming from the center, manifold area. When I spray cab cleaner while running no change of idle of engine.

 

Well stopped by Advance Auto today and had a guy check the truck with the code reader. It was giving the same ole 171 and 174. We talked about a possible vac leak, so he checked under the hood. Guess what, the dude found it......I could have hugged him. He located it by the EGR valve on the manifold which connects to the PCV valve. It was an elbow hose. He took it off and you could stick your little finger in it. It was dry and brittle. Went to the dealership and got a new one and re-set the compter. So far so good...It for sure idles a ton better....Feels like I'm driving a new truck. Thanks for all that responded to this thread. And a big thanks to my Dad, who knew the problem was such, but we couldn't find the damn thing.

 

[QUOTE=gijoeguy/ford]Well stopped by Advance Auto today and had a guy check the truck with the code reader. It was giving the same ole 171 and 174. We talked about a possible vac leak, so he checked under the hood. Guess what, the dude found it......I could have hugged him. He located it by the EGR valve on the manifold which connects to the PCV valve. It was an elbow hose. He took it off and you could stick your little finger in it. It was dry and brittle. Went to the dealership and got a new one and re-set the compter. So far so good...It for sure idles a ton better....Feels like I'm driving a new truck. Thanks for all that responded to this thread. And a big thanks to my Dad, who knew the problem was such, but we couldn't find the da n thing. [/Q That light dose drive you mad took me three weeks to fine the fault as not many garages carry the software to read american trucks in the uk.