Code: PO171 Bank One Lean

[Jon1960]

To Whom it may concern,
I have a 1998 Jeep Cherokee, 4.0 6cyl. I was on the road last week and my Jeep started to stall at high RPM,s. It seemed to happen mostly while either trying to accelerate at high speeds, or going up a long, steep grade. But at least once, it occurred when I was driving steady on a level roadway. Finally, the engine died and the "check engine light" came on. The engine started right away, and I hobbled to the next town. I filled up my gas tank, and the problem seemed to go away until my tank dropped down to about half full, then the stalling started again. I ended up getting a fault code readout at a Checker Auto. The code was PO 171. I have been doing some checking on the internet and it seems to point to either a faulty O2 sensor, MAF sensor, or a vacuum leak. Any ideas that may narrow this problem down? If it is a leak, where would it most likely be located? Any answers would be appreciated. Thanks.

Jon

[LauraBoston]

hey,
i see this a lot in caravans, never seen it in a jeep. i'v always come down to changing the fuel pump (but the problem is the pressure regulator). Or, it could be a restriction in a line. If you can get your hands on a fuel pressure tester, see if the pressure is high...then you know it's a pump.

Otherwise, Chrysler says it could be:
O2 Sensor
O2 shorted to ground
O2 heater operation
TPS voltage greater then .92 w/throttle closed
TP sensor sweep
Map sensor operation
ETC sensor operation
Engine mechnical
fuel pressure high
or PCM

Personally, I'd start with the fuel pressure.
A vacuum leak you'd normally hear...usually they are loud, you can get some carb cleaner and spray it arond the intake and what not, and if the engine surges it has sucked in some carb cleaner and you know there is a leak around there...good luck.

	Throttle position sensor A throttle position sensor (TPS) is a sensor used to monitor the position of the throttle in an internal combustion engine. The sensor is usually located on the butterfly spindle so that it can directly monitor the position of the butterfly throttle valve. The sensor is usually a potentiometer and therefore provides a variable resistance dependent upon the position of the butterfly valve (and hence throttle position). The sensor signal is used by the Engine Control Unit (ECU) as an input to its control system. The ignition timing and fuel injection timing (and potentially other parameters) are altered depending upon the position of the throttle, and also depending on the rate of change of that position. For example, in fuel injected engines, in order to avoid stalling, extra fuel may be injected if the throttle is opened rapidly (mimicking the accelerator pump of carburetor systems).

[Bounty__Hunter]

Googled it.

Basically this means that an oxygen sensor in bank 1 detected a lean condition (too much oxygen in the exhaust). On V6/V8/V10 engines, Bank 1 is the side of the engine that has cylinder #1.
You will more than likely not notice any drivability problems, although there may be symptoms such as a lack of power, detonation (spark knock), and/or a hesitation/surge on acceleration.

A code P0171 may mean that one or more of the following has happened:

The MAF (Mass Air Flow) Sensor is dirty or faulty. Note: The use of "oiled" air filters (K&N, etc.) can cause the MAF to become dirty if the filter is over-oiled
There could be a vacuum leak downstream of the MAF sensor.
Possible solutions include:

In the vast majority of cases, simply cleaning the MAF sensor does the trick. Consult your service manual for it's location if you need help. I find it's best to take it off and spray it with electronics cleaner or brake cleaner. Make sure you are careful not to damage the MAF sensor, and make sure it's dry before reinstalling
Inspect all vacuum and PCV hoses, replace if necessary
Check for a dirty fuel filter and proper fuel pressure

[lippy]

I had same problem burped at high rpm. and code 171 and the problem was the O2 sencer under the hood. it is the 4 wire sencer 60.00 at auto zone. now runs great and getting 3 mpg better