Lack of bank 1 O2 Transitions

[boitnottnj]

New to the forum. Having some problems with my 2003 F150, 4.2L V6. It has about 106000 miles on it, and just about two weeks ago start idling funny. After initial warm-up, when the rpms droped down to normal, the rpms would constantly jump between 750 and 1000 like I was barely tapping the gas.

The check engine light came on yesterday and I took it by autozone so they could run the code. What it came back with was: Lack of bank 1 O2 transitions - Lean explanation - Detected bank 1 O2 at its lean limit.

Proable causes were a misfire on bank 1; vacuum leak affecting bank 1 only; or a fuel injector problem bank 1.

I can hear an accessory kicking on and off constantly when it is idling so I am thinking that it is a vacuum leak but I am not sure. Any advice on how to check vacuum pressures on things only affecting bank 1. Also, what and where is bank 1??

Any help would be appreciated.

[way2old]

Please post exact code number. That will help us research your problem. Thanks

[boitnottnj]

The code number is P1131

Hope this helps

[dfordski]

Dup

[dfordski]

P1130/1131 - Lack of HO2S-11 Switch, The HEGO Sensor is monitored for Electrical:
Fuel Trim at Limit switching. The code will set when
the HO2S fails to switch due to •Short to VPWR or VREF in harness or
circuit or fuel at or exceeding a HO2S
calibrated limit. •HO2S circuit shorted to Ground
•Water in harness connector
•Open circuit
•Corrosion or poor mating terminals and
wiring
•Damaged HO2S
•Damaged PCM (other DTCs should be
present)
Fuel System:
•Excessive fuel pressure (stuck fuel
pressure regulator, restricted fuel return
lines, etc.)
•Leaking/contaminated fuel injectors or fuel
pressure regulator
•Low fuel pressure or running out of fuel
(fuel pump concern, fuel supply line
restrictions, low fuel level, etc.)
•Vapor recovery system (stuck VMV, etc.)
Induction System:
•MAF contamination
•Air leaks between MAF and throttle plate
•PCV system / Other vacuum leaks
•Improperly seated engine oil dipstick
EGR System:
•Leaking gasket
•Stuck EGR valve / Leaking diaphragm or
EVR
Base Engine:
•Oil overfill
•Incorrect cylinder compression
•Exhaust leaks before or near the HO2S
•Secondary air stuck on

[RahX]

Sounds like an O2 sensor would be a good place to start.

[dfordski]

Originally Posted by RahX

Sounds like an O2 sensor would be a good place to start.

Heck ya. I'd start with the Sensor. It should be the front sensor on the #1 cylinder side. If this takes care of the problem, you should replace at least the other o2 off the other manifold at the same time to ensure They both share the same accuracy & switching speeds. 1 new and 1 old is a bad idea. The ones after the Cats are more for monitoring Cat health and less to do w/ driveability & MPG. But, replacement of all would probably be best thing to do. I would look hard for a Vac leak & ensure the integraty of the Ignition system. Read your Plugs. I replace my 02 sensor 35-50k(but I only have 1 on my 87'). I do get 18/23 MPG w/ my 302.

[RahX]

x2 I agree with dfordski

[boitnottnj]

Thanks for the help. Took my truck to get new tires on it today and had them run the code as well and they came back with the gas cap was not holding pressure because the gasket was wrikled up or something and replaced the gasket and reset the check engine light.

I do not really think this was the problem and if it continues to idle rough, I will look into replacing the O2 sensors. Just finished replacing all 4 on my wife's 2003 montero sport so I am tired of spending money on O2 sensors.

Once again, thanks for the help

[danielsatur]

We never replace the down stream HO2 sensors, they just tell the ECU/PCU if the catalyst is good on your cats.The upstream are more important, because the are used by the ECU/PCU for the Air/Fuel mix.

[boitnottnj]

I lied about replacing all four in my wife's montero sport. I have ordered the two upstream sensors and actually replaced the two downstream sensors. After replacing the two sensors after the cats it made a significant improvement on how it ran. Before replacing it ran very rough and would start missing when going up hills and accellerating. It still doesn't run 100% but is much better.

Would replacing the upstream sensors fixed the problem without having spent the money on the two downstream sensors? This would also be helpful if I have to replace the O2 sensors in my F150.

Thanks

[dfordski]

Originally Posted by danielsatur

We never replace the down stream HO2 sensors, they just tell the ECU/PCU if the catalyst is good on your cats.The upstream are more important, because the are used by the ECU/PCU for the Air/Fuel mix.

You missed this post!

[danielsatur]

Some people have money to throw parts + service at all four sensors.
We focus on root cause, and only replace as needed.

The most probable cause, because Age + mileage (2003/106k miles) is MAF sensor contamination.

A little routine maintenace needs tobe preformed 1st,

1) Air filter / PCV valve
2) Clean MAF/IACT sensors.
4) Clean throttle body.
5) Reset and clear code.

* A bad PCV system will contaminate the Air filter, MAF, and IACT sensors with oil.
The MAF sensor is a electronic metering device, that's probably sending the wrong data to the ECU/PCU during cold starting!

[dfordski]

Originally Posted by danielsatur

Some people have money to throw parts + service at all four sensors.
We focus on root cause, and only replace as needed.

The most probable cause, because Age + mileage (2003/106k miles) is MAF sensor contamination.

A little routine maintenace needs tobe preformed 1st,

1) Air filter / PCV valve
2) Clean MAF/IACT sensors.
4) Clean throttle body.
5) Reset and clear code.

* A bad PCV system will contaminate the Air filter, MAF, and IACT sensors with oil.

When your religious about maintenance you sometimes forget that most people aren't, and alot of maintenance only occurs during the process of determining a malfunction. Better late than never I guess. At 100K I'd like to add removal and cleaning the EGR & it's intake manifold portways. I also tend to replace my o2 sensor before the Cat after 35K or so. Partially for maximal fuel trim (18/23mpg w/87' 302) and partially out of boredom, waiting for something to malfunction (which isn't very often). The Fuse just blew for the wiper's (Whew-hoo!) In CA., long as I replace it by April or May, I'll be fine.

[danielsatur]

How come it's legal to smoke pot in CA, but your cars can't?