Newbe here From Oregon

[ExploreOregon]

I have a 99 xlt with 4.0L I'm not sure where to post this question so here goes. I need help with check engine light and code P0171 SYSTEM TO LEAN BANK 1.
I need to learn how to do my repairs now that I got let go from work. Tough times. Thanks ,
Tony:exp:

 

[BrooklynBay]

Welcome to this forum! Check the intake manifold gaskets, and vacuum lines for leaks. Sometimes bad spark plugs could throw this code too.

 

[Sams01XplrSprt]

welcome

 

[gijoecam]

Which 4.0 motor is it? The OHV or the SOHC motor?

I'd second the intake gaskets... the repair procedure varies based on which motor it is...

-Joe

 

[ExploreOregon]

OHV I believe

It's new to me. I am sure it's an OHV. I haven't looked at the tune up parts yet. It does have a new air filter, fuel filter, and I am going to buy the PCV valve. I will look closer today at the engine type and install new plugs. The guy at the AutoZone told me I need to replace the two Oxogen sensors. I need to hold out on these two items do to the cost. Trying to keep the costs down.
More tonight.

 

[gijoecam]

It's new to me. I am sure it's an OHV. I haven't looked at the tune up parts yet. It does have a new air filter, fuel filter, and I am going to buy the PCV valve. I will look closer today at the engine type and install new plugs. The guy at the AutoZone told me I need to replace the two Oxogen sensors. I need to hold out on these two items do to the cost. Trying to keep the costs down.
More tonight.

The guy at AutoZone is an idiot and doesn't have your best interests in mind. Just because the oxygen sensor is reading a lean condition (and it's only ONE oxygen sensor giving that reading, not both) doesn't mean that they both need to be changed (and which two did he want you to change? The upstream sensors or the down stream sensors or one of each??) The guy at AZ won't tell you that maybe, just maybe, the oxygen sensor is reading correctly and the engine is, in fact, reading a lean condition in bank one just as it should.

That can be caused by a leaking intake manifold gasket on that side of the engine, as well as any sort of vacuum leak on a line connected to that side of the intake manifold. It *could* also be a fuel pressure issue on that one side (if the fuel lines happened to be routed that way, but I don't think they are). Odds are it is, in fact, running lean on that side due to a leaky intake manifold gasket. Common problem, simple solution for any DIY'er. If you can do brakes, you can do the IM gaskets on either motor. There are how-to's for both of them on this site somewhere...

Good luck!

 

[alohamonte]

Welcome fellow Oregonian.

It's good practice to do some routine maintenance whenever you get a new-to-you used car. Don't trust the past owners to have done the maintenance on YOUR car.

When you replace the PCV, make sure that it's seated flush to the valve cover gasket and that the little hose is in good shape. I had a vacuum leak at the PCV very recently because it was unseated. Gave me a stumbling idle (no CEL).

 

[ExploreOregon]

May have found problem.

I went and got spark plugs and PCV Valve. I found that who ever replaced the spark plugs last, didn't replace the ones in the right rear. I don't know what numbers they are. It was a B..... (Bummer) to get to the last one. I went from underneath and got it that way. They were Motorcraft and rusty. The other four were Autolite. But, when I got under that area, I looked up and saw one screw missing from the exhaust flange to the pipe just before the CAT. The exhaust was jiggling loose. I'm wondering if this may have something to do with it. Any way it runs much better now. More power I believe because of the spark plugs. The PCV valve was brittle and not too happy, and the hose was really soft and gooee. The light has not come on yet. Hope you can see these pics. Thanks again for all the help. The spark plugs were cheap and I used a screw with a spacer for the exhaust flange missing screw. See picture.
Oh and, is this the side where Bank 1 resides? If not, I may be chasing a ghost.
Thanks,
Tony.
:exp:

 

[96eb96]

That could ABSOLUTELY cause an O2 sensor code. It lets air in and makes a "lean condition." Exactly why you don't replace parts because of a code.

 

[robertoa1a]

I agree with the above. Any time money is tight it pays to spend time bringing your maintance up to date before trying to troubleshoot. I see too many people changing parts out left and right only to find out they had a simple vacume leak.

O2 sensors often take the blame for other simpler and cheeper problems. Take your time and go through everything to spot all the neglect from the last owner.

You can get un-real milage out of an explorer with just regular maintenance.