• Welcome to the Contour Enthusiasts Group, the best resource for the Ford Contour and Mercury Mystique.

    You can register to join the community.

P1151 and Rough Idle - Are These Related?

G

gliderjoe

New CEG'er
Joined
Mar 24, 2004
Messages
22
Location
San Francisco
About 3 weeks ago I experienced a P1151 code. I cleared the code, and it has not come back since. About a week ago I had some rough idling issues, but that went away as well the next day. Would these two things be related? Should I expect to have to change out the forward O2 sensor soon?
 
You probably have a vacuum leak. Spray with carb cleaner. If idle changes, you found the leak.

From TSB,

P1151 - Lack of HO2S-21 Switch, Indicates Lean, Bank 2 Upper sensor

When an HO2S sensor indicates lean at the end of a test, the system is trying to correct for an over-lean condition. The code is set when the fuel control system no longer detects switching for a calibrated amount of time.

.Electrical:
· Short to VPWR or VREF in harness or HO2S
· 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
 
Last edited:
I ended up changing the upper front O2 sensor with the AutoZone Bosch one for $60. My car runs so much smoother now, and the P1151 error is gone. What a difference good O2 sensors make. Im thinking about changing the other 3 as well in hopes of even better performance.
 
gliderjoe said:
I ended up changing the upper front O2 sensor with the AutoZone Bosch one for $60. My car runs so much smoother now, and the P1151 error is gone. What a difference good O2 sensors make. Im thinking about changing the other 3 as well in hopes of even better performance.
Click to expand...



Whoa, there, Joe.

Replacing ALL the O2 sensors is a waste of your money. The downstream sensors have nothing to do with the engine's fuel control, they are only there to monitor the performance of the pre-cats.

If you're inclinded to spend $60, skin some knuckles, and generally use all your vocabulary of cuss words (and make up a few more), then replace the upstream Bank 1 sensor.

Steve
 
projectSHO89 said:
Whoa, there, Joe.

Replacing ALL the O2 sensors is a waste of your money. The downstream sensors have nothing to do with the engine's fuel control, they are only there to monitor the performance of the pre-cats.

If you're inclinded to spend $60, skin some knuckles, and generally use all your vocabulary of cuss words (and make up a few more), then replace the upstream Bank 1 sensor.

Steve
Click to expand...

:laugh:

All of this is correct info, but I just had to laugh (having done the above in bold). With large mits like mine, it is especially challenging.
 
Tony-You mentioned a vacuum leak and said to spray with carb cleaner. What are you spraying the carb cleaner on? I have a feeling I may be having this prob.

Thanks in advance.
 
You are spraying on the vacuum hoses or intake manifold gaskets. Just in case, the hose clamps are loose or there is a crack that is not visible to the eye. If it is and exhaust leak, then you will usually hear a ticking sound near the offending item. Most times, to get a code due to an exhaust leak, it is near the precats, i.e. near the O2 sensors.
 
You must log in or register to reply here.
Back
Top