Frequent loss of 02 sensors..

AesclepiusCrow

New Member
Sep 4, 2009
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I purchased a 98 Mustang LX V6 a while back. Check engine light came on soon after, thought nothing of it, code P1151. Mechanic stated 02 sensor needed replaced and did so. However, this past week, the check engine light has come on again, again diagnostic code P1151. This is a light driver, 2-3 days a week out of the garage. Maybe estimated 800 miles since last 02 sensor change, if that. Idle is still what it has been since purchase, about 600-700rpm.

Obviously, the answer is not to replace an 02 sensor every 6 months. Mechanic has suggested a possible short in the wiring of 02 sensor. Can anyone else help me shed a little more light on what may or may not be going on, so I can minimize time in the shop chasing ghosts?
 
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3.8 liter V6 head gasket leak

I hate to bring bad news, but there is a high likely hood of a head gasket leak. The leak is allowing coolant in the exhaust. The coolant is ruining the O2 sensor.

Note, the O2 sensor can also be ruined by excessive amounts of fuel or oil in the exhaust.

Since the 3.8l V6 is bad about blowing head gaskets, I would start there. Does the car use coolant? What is the color of the exhaust? Consider having the coolant system pressure tested.

Do not recommend continued driving as this will also ruin the cats.

The other possibilities need to be ruled in or out (excessive fuel or oil in the exhaust).

Does the car use oil? If so, how much? What is the color of the exhaust? Does it foul plugs? How's the gas mileage?
 
Oil usage is standard, exhaust is no more noticeably different than any other vehicle, though I do not quite have the eye to determine small differences that might occur. Gas mileage doesn't seem to have changed much but I will keep an eye on it over the next few days. Also will check the plugs and reply again afterwards.
 
You need to find out where the contamination is coming from. How much oil or coolant is used (dissapears) from the engine. Could it be an intake manifold leak? As stated Head gasket is a possibility also, look for champagne bubbles in your coolant or an oil film at the rad filler cap. . Maybe put an OEM sensor in this time?
Suggest an compression or leak down test,
Aeroman.
 
Sorry about the disappearance, guys. Midterms -- they eat all your spare time.

The coolant and oil seem fine, no bubbles in the coolant. Also, a few days ago, the engine light shut itself off. I am wondering if this confirms the harness short? I'm in a heavy snow area and the light shut itself off as everything finally thawed out again, could this be related at all? Either way, I'm hoping it at least makes this a much less serious issue. Send me some good news.

Any further ideas, gents?
 
Run a coolant system pressure test

Head gaskets don't repair themselves. If there is coolant in the exhaust, continued use will corrode the material in the head/block as well as ruin O2 sensors and cats.

A coolant pressure test will rule this in or out.

This could be a wiring fault. But, if the O2 sensor has been confirmed contanimated with a visual inspection, the odds do no favor you. Esp since so little time/miles have elasped since the last repair.

>>From Ford service CD
P1151 - Lack of HO2S-21 Switch, Sensor Indicates Lean

A HEGO sensor indicating lean at the end of a test is trying to correct for an over-rich condition. The test fails when fuel control system no longer detects switching for a calibrated amount of time.

See Possible Causes for DTC P1130
P1130 - Lack of HO2S-11 Switch, Fuel Trim at Limit

The HEGO Sensor is monitored for switching. The test fails when the HO2S fails to switch due to circuit or fuel at or exceeding a calibrated limit.

Electrical:
Short to VPWR in harness or HO2S
Water in harness connector
Open/Shorted HO2S circuit
Corrosion or poor mating terminals and wiring
Damaged HO2S
Damaged PCM
Fuel System:
Excessive fuel pressure
Leaking/contaminated fuel injectors
Leaking fuel pressure regulator
Low fuel pressure or running out of fuel
Vapor recovery system
Induction System:
Air leaks after the MAF
Vacuum Leaks
PCV system
Improperly seated engine oil dipstick
EGR System:
Leaking gasket
Stuck EGR valve
Leaking diaphragm or EVR
Base Engine:
Oil overfill
Cam timing
Cylinder compression
Exhaust leaks before or near the HO2S(s)