please help 99 xls with bank 1 running lean. code p0171

[IDNTH8T]

hey every 1 newbe here trying to figure out whats wrong with my 99 xls 4.0 ohv 2wd. The first time my chk engine light came on I got the code P0171 i then checked the code & it said bank1 fuel trim (running lean, oxygen sensor defect, fuel injector, misfire or vacuum leak, MAS. I changed the oxygen sensors replaced the plugs & wires & noticed the plug on the cylinder closest to the firewall left side if your facing the front of vehicle is running lean all other cylinders look good. plse if anyone can help it would be greatly appreciated. thks :roll:

 

[badgett]

Sound like the injector for that cylinder is stopped up. Try getting your injectors cleaned or try some good injector cleaner.

 

[dogfriend]

Info on P0171

 

[dogfriend]

continued

 

[Glacier991]

High on my list of "usual suspects" in your situation (and off the list so nicely provided by DogFriend above) is a vacuum leak, more specifically an intake manifold gasket leak.

 

[Turdle]

Check # 4 fuel injector
usually a vacuum leak will effect #1 and #8 with a lean, unless maybe a vacuum leak at the injector bung of #4 injector, also a cracked exhaust would effect #4 more than 1-3 ( shortest runner)

 

[rangerben446]

It could very well be the start of a problem with the intake manifold gasket. I had the same problem, and it started out small with the same code (P0174 started to show later). It got worse over time and eventually it began to have a hard time starting cold and a rough idle. After various other repairs, I put in a new upper and lower manifold gasket and it cured the problem. If you look at the past messages, you'll see that this is a real problem with explorers.

 

[IDNTH8T]

I just cleaned the MAS and put some fuel injector cleaner w/ a full tamk of gas. But i dont think ill know if the problem is gone until the chk engine light comes on again. is there a way to check or find a vacuum leak? i thought other cylinders would be affected if there was a leak but its only one (right now) should i replace the manifold gaskets first? or replace the injector from the cylinder thats runing lean?

thnks again guys

 

[jp450]

I just cleaned the MAS and put some fuel injector cleaner w/ a full tamk of gas. But i dont think ill know if the problem is gone until the chk engine light comes on again. is there a way to check or find a vacuum leak? i thought other cylinders would be affected if there was a leak but its only one (right now) should i replace the manifold gaskets first? or replace the injector from the cylinder thats runing lean?

Start with the intake gaskets. They are cheaper and more than likley the cause of your problem.

 

[blondepms9489]

having the same issuses, cept i replaced the intake gaskets and still isnt fixed and now it seems to be running worse...

 

[Oxygen]

i had the same code last week too, it ended up being my intake manifold gasket.. i hate inspection stickers

 

[Dingy0540]

lol mine is doing the same thing. but i cant find any vacuum leaks. but i dont see any reason not to spend the extra few dollars to replace the intake manifold gasket