I looked but the hose was wrapped with about 3/4 of an inch of insulation and I didn't see how to get it off without destroying it. But there wasn't any oil or anything leaking out of the insulation anywhere. I was experimenting with some electrical modification of the headlight fog light control on the truck and had the battery disconnected. When I pluged it back up and hit the road for about 5 miles the light hasn't come back on yet.

If it does come back on, are these O2 sensors cheap enough that I can just buy 2 of them and replace the 2 on the drivers side and see if that was it?

 

O2 sensors are not too expensive but it is very easy to check them. Just unplug the sensor from the harnes and use a multimeter to measure resistance. It will say in you Haynes or Chilton manual what a good O2 sensor should read. Then replace the bad one. That is if one of them is bad.

 

I am electronic dummy, can you explain to me how to check it, and talk to me like I do not know anything? Electricity is my weakness I do not know too much about it. Thanks

 

You can use any meter that measures resistance. If you don't have one, they can be had at any parts store for under $10. Set the meter to resistance (the symbol will look like an upside down horse shoe). Find where the wires from the O2 sensor connect to the harness. Then unplug it and place one lead from the meter on each terminal of the plug. You should get a reading of just a few ohms (less than 10) or some symbol either an OL or infinity. The OL or infinity symbol means it is open. I looked in my Haynes manual and couldn't find the correct reading listed. I know I have seen this listed in the Chilton manual but I can't find it (go figure). You could buy a new sensor and measure it. Compare it to what you measured on the one in your truck. Hope this helps.

 

I realize that this post is a few months old, but I have a 1997 F-150 4.2 2WD with 270,000 miles. About a year ago, I started to get a rough idle from time to time -- not always. The check engine light would eventually come on. After disconnecting the battery to get the CEL to go off, it would stay off for a month or two. Eventually, the rough idle would return, and I would repeat the process.

In the last couple of months, I have noticed that the idle is getting VERY rough at times. One thing I have noticed, is that it generally is worse in high humidity or raining, but not always.

I took it to one of the Auto parts places and got Lean on Bank 2 and bank 2 Codes 170 and 174. I have not checked the O2 sensors yet, but did clean the MAF with electrical cleaner and replaced the air filter. After starting it up, it is idling worse then ever -- sort of a loping thing. New air filter made it even leaner, LOL and it is overcast and humid. Can the MAF be bad even if the wires are not broken?

I kind of doubt both O2 sensors would go bad at the same time. The relationship with humidity is what gets me.

Any thoughts? Just a reminder that this is a 4.2 not a 4.6 as indicated on the first post.

Thanks for all your help.

Mark

 

I meant Bank 1 and Bank 2. Sorry.

Mark

 

hi mark, i would first check plugs and wires and vacuum leaks as these 4,2 seem to be super critical regarding a good spark. good luck bokker.

 

Hi Bokker,

Yeah, I generally have to replace the wires about every 75,000. I usually get a sort of mid-range miss when they go bad. This is the first time I have had a vehicle with this many miles -- I am the original owner. It gets to "Didn't I just do that?". Oh, that was 100,000 miles ago.

I think it is time to replace the plugs and wires anyway, so I guess I can start there. If you have seen the top of a 4.2, it is next to impossible to even see the PCV, let alone try to find a vacuum leak as suggested in the other posts. It would seem like a vacuum leak would be there all the time and not give the inconsistent issue.

Since it is worse when humidity is high, I was thinking electrical. Would one missing cyclinder give the rough/loping idle?

Thanks, Mark

 

Cjeck you PCV hose elbows as well. Could have a vacuum leak there if they are real soft.

 

hi again mark, yes one cylinder chiming in and out could give you a problem. as lxman1 states that dam elbow rubber is very lightly to give the symtems and it is there to be seen and checked, you will find it under the intake manifold at the front. its worth a look see. bokker.

 

I'll definitely take a look at that. You say it is under the intake manifold in the front? Is the PCV stuck in the right side (passenger) rocker-arm cover? I had the intake manifold off a few years ago to replace the two little clips all the way at the back, but forget where everything was.

It is raining at the moment and has been off and on all day. Won't complain as it has been sort of a drought down here most of the summer. I'll let you know when I find the problem.

Mark

 

Long story short, started it up and turned off A/C. Definite hiss that seemed like it was in the fornt or in the back depending on where you stood. Turns out, it IS in both places. The parts guy at Ford agreed with LxMan1 that the rubber elbow in the front tended to get hot, soften and get a hole sucked in it. LOL

Took it off, and low and behold, a dried-pea size hole sucked right in the outside corner of it. This elbow is found on the end of a hard plastic hose right underneath the front of the intake manifold as Bokker said. The PCV itself is all the way in the back on the right-hand side rocker-arm cover. On the left, looking from the front. The PCV hose goes from there and snakes its way under the intake ports to the front where it turns to the right and has the elbow on the end.

After I replaced the front elbow, it ran just as badly as it was. Listened under the hood again, and there is still a definite vacuum leak, but in the back.

So is there another one of those elbows in the back? I replaced the PCV while I was at it, but I have no idea how the hose is put together from there to the front. Is it one rigid piece like a "Z"?

Thanks for all ur help, Mark

 

hi mark pleased you found some thing as for the pipe work from front to back, i am unable to help you as here in the uk there are no spares and i made-up the pipe with standard petrol pipe. bokker.

 

I got one of the entire PCV hose assembly from the Ford Dealer. I think it was around $12 or so. It was not much more then the one elbow I got yesterday and the same elbow came with the assembly.

I have not replaced it yet and can not wait to try to thread it through under the intake ports. I have a feeling the short rubber hose that connects the PCV to the pipe has a split in it. It turns easily on the pipe. The parts guys say nothing really ever happens to the rigid part.

I will let y'all know wheneverything is straightened out. Going out to work on it now.

Mark

 

Well, replaced the entire PCV line. I did not see anything wrong with the rest of it. Still sounds like there is a vac leak somewhere. Tried to locate it last night using a piece of hose to no avail.

Idle still rough here and there. I cleared the CEL by disconnecting the battery. Has not come back on yet, but I am expecting it to so I'll check the codes again at that time and see if there is anything new.

Are there any vacuum lines that I might have pulled loose or might be broken behind the engine?

Thanks, Mark