It can be a real pain if the studs are corroded.

 

True that!

On my 97 5.4, I had to remove the dipstick, and disconnect the egr and part of the steering on the drivers side. Then there was the drilling out of the broken bolts... I ended up just getting headers to pay myself back for the agony!

 

So what type of headers did you wind up getting? I want to do some for my truck.

 

So I threw another code today PO0155? I think that is what the guy at auto zone told me. I know it is related to the fuel filter and it also pulled an 02 sensor code go figure Tomorrow night my Father-in-law and I are going to work on it! I got the fuel filter too. Should be fixed soon! One question. After I change the 02 sensors and the fuel filter do I have to manually scan the truck and remove the codes or will the light go off on its own. My91 mustang that I had as soon as you replaced the defective parts the light would immediatly shut off. Are these trucks the same way?

 

P0155 - Oxygen O2 Sensor Heater Circuit Malfunction (Bank2, Sensor1)

Not related to the fuel filter. You have a bad front O2 on the driver's side or a wiring problem.

I'd disconnect the battery while doing the work to clear the computer, unless you are due for inspection soon.

 

Yea, they can corrode up pretty good, - It's really not all that bad, - if your equipped to hack the exhaust and piece in new , or headers. The exhaust take the longest I guess. - That's IF your changing things up. Other than that, it wasn't bad with the right swivels. I used an impact on all/ installed LT's w paper gaskets. I have metal ones on the shelf. The paper hasn't leaked for three years so far... Yea, I don't believe , but they don't leak, - I can promise you that lol.

 

Ok o2 sensors replaced on Sat. Light went off. Driving on Sun light on again. Same po0171. I replaced the PCV valve a few weeks back. My guess is to just replace all the white colored vac lines going to the throttle body as well as the line that connects the PCV valve to the TB. Is the hard black hose on the left side of the TB that has a Ford part no. on it a stealership only part? I just want to replace all the vac lines as they are old and I have 164xxx miles. I know that there is not too many vac lines so I should just eliminate the vac prob all in one shot.

 

wookie13, Any updates on your po0171 problem?

I have an irritating very intermittent P0171 & P0174 problem on my 2002 F150 4.2L. I have been searching the forums the last 5 months for answers. We have been looking, poking, feeling, squeezing, shaking, pounding, 4 people jumping up and down on bumpers, LP gas & smoke testing , with no resolution to date. It will pop a hard code every 2 to 3 weeks. We have found it will pop a code sometimes if driving slow off road or driving slow over a speed bump. Sometimes it will have a hard 171 along with a pending 174. Idle is normal, drives great, good power, just the intermittent codes.

 

Well both of my codes Po171 and 174 went away on their own last Wed. So far the light has been off. My guess is that the PCM was running off of the old data from my old ox sensors that had 164xxx on them.I have heard that the PCM somtimes goes into what is called a "closed loop" mode when the 0x sensors malfuntion. My truck ran fine thru all of this except it would use a lot of gas due to it being in closed loop mode. So far my fuel milage has picked back up.

 

hey im getting this codes i noticed u got the same one and it wont go away po401 po174 po171

 

Closed-loop is a good thing. It is one of two fueling situations based on criteria from your engine. Your truck is open-loop (meaning coolant temp low, O2s not heated enough or TP is high) when you first start it on a cold day. In closed loop fueling, the computer takes readings from everything and based on sufficient parameters, allows less fuel burn. Temp is ~195*, TP is low, and the oxygen sensors, which read +/- of 14.64 AFR (Stoich) and makes corrections for it. If your truck is idling @ 13.5 AFR, the 02s can see this, and will know to pull out enough fuel to get back to stoich.

 

Light came back on this morning. Truck is using a LOT of gas again! Filled up and went 80 mi truck used a 1/4 of a tank WTF? Truck runs FINE no hunting idle or miss. It just uses a TON of gas! Also the exhaust reeks bad like rotten egg smell! I am completly stumped!

List of what I've done to it so far:

New plugs/coil packs-Motorcraft
coolant flushed
transmission flushed
differentails/ transfercase flushed
done in July 2009

New OX upstream sensors 3 weeks ago
new MAF{under warrenty at car quest to replace defective unit}NEW PCV valve and hose going to TB, replaced a hose that was dry rotted on back of TB

Cleaned TB checked and re-checked and checked again for vaccum leaks

I don't know where to go from here!! Its really starting to **** me off!!

 

Its most likely the cats. My exhaust was stinky rich too. Turned out to be the cats.

 

For what its worth, this was how my P0171 played out:

My 2001 SuperCab sat for a year waiting for a used engine transplant. During that time, the inside of the fuel tank started to corrode. When the truck was back on the road, the junk in the tank slowly started to plug up the fuel filter and the tiny filters at the inlet to each of the fuel injectors. I cleaned the tank, replaced the fuel pump sock, replaced the fuel filter and sprayed out the little injector filters with carb cleaner. Now two months later, everything is back to normal. In the end, the lean condition was due to restricted fuel flow.

 

You still have not checked fuel pressure and ability of the fuel regulator to work.
As soon as the OX sensors shift out of range or become inoperable for any reason, the fuel system goes into "open loop" meaning the motor is being fuel controlled from a 'fixed' fuel table that is, by design, is RICH for engine protection, hence fuel mileage suffers.
The next step is to use a scanner to look at the parametes to see what is out of operating limits. This is why the diagnostic ability was provided.
After all what would you think a good dealer shop would do the find the issue?
Good luck.