PLZ HELP 01 ford explorer

[b1blazin]

im a learning mechanic and im not familular with alot! ive looked and looked to no avail. i have many questions lets start:

I have a p0171 code 1bank too lean i have a obd2 with live data but i cant find a vaccume leak anywhere one of my o2 shows the v at 1.275 and stays there. all rest seeem to fluctuate normally. I see that o2 sensors are located under neath around the catalitic converter but i dont know which is which or what to try or even if o2 is my problem instead of intake manifold gasket which is a common problem aswell as the torn elbow i dont see.

i tried to blow smoke in there but dont see any escaping. i checked the MAF sensor but it seems clean to me and reads on obd2 live data.

its hard to start on cold mornings other than that idk. my fuel trims are high for bank 1 like 20 something.

what should i do?

 

[Rick]

I'm going to move your thread to our Stock 1995 - 2001 subforum where the right folks should see it.

One place I have seen vacuum leaks occur which a lot of people miss is the vacuum hose and/or elbow to the power brake booster.

 

[Robman]

A relatively common problem on the 4.0 SOHC is the intake gasket or o-rings.. whatever they are shrink in the cold and provide the problem you're describing.

I haven't needed to pull the intake off of mine so, I'm just speculating.

I think some people spray some sort of liquid, maybe starting fluid? Around there to see if the idle goes up.

 

[b1blazin]

ive heard this before. i sprayed carb cleaner and wd40 a different time to see if it effects anything but too hard to tell cant see any major change in idle it might be the gaskets since its common problem but why doesnt it change when sprayed or no smoke.

 

[2000StreetRod]

O2 sensor voltage

The O2 sensor voltage of 1.275 volts is probably bogus. What is the name of that PID? The normal O2 sensor voltage range is .1 to .9 volts. Your scanner that is providing the live data is probably unreliable for the PID you have selected. Try a different PID for the same thing. There are usually multiple ones to pick from. As Robman posted if you have the SOHC V6 with the original intake manifold gaskets they are probably dried out. They shrink with cold temperature and allow unmetered air (didn't get measured by the MAF sensor) to enter the intake ports. I'm surprised it's only on one bank. What are your long and short term fuel trims for both banks? The only reliable method for finding intake vacuum leaks is to use a smoke machine.

 

[Glacier Explorer]

Get a can of MAF sensor cleaner, and spray the sensor down thoroughly. It may look fine, but it couldn't hurt to do that. I checked all hoses (which were fine) and sprayed some leftover MAF cleaner around the intake manifold. I couldn't hear or observe an idle change either. I decided to just replace the upper and lower intake manifold gaskets to see if that would solve the issue. Sure enough, the CEL went off and never came back.

For reference, I have the 4.0 SOHC, and the CEL came on at about 140k miles. To my knowledge, I replaced the factory gaskets, which were obviously the issue once the manifolds came off. Took a few hours and less than $50 to fix the problem.

 

[Macgiobuin]

Check fuel pressure. Should be 60-65 psi; if less, you could have fuel pressure regulator problem (in the fuel tank) or a leaky pressure regulator housing or hoses there.