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Followup To
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Hey John,
Thanks for any insight you can provide. I just recently brought my 96 Disco 4.0 into the dealership for a check engine light and some rough running. (broke my heart to do this because dealership is 80 miles away, and I hate them). Anyway, they informed me my trouble was an o2 sensor (only one). After getting the part from Atlantic British, (dealership wanted $387.00 US) they installed it for me ($85.00 US, 10 minute job) and cleared my light. Driving home that evening the light came back on. Called dealership, they told me they thought that may happen as another o2 sensor was showing signs that it may also fail. I was told to bring it back in and for another 2 hours labor charge ($170.00 US) I could bring them another sensor and they would install it and reset the light again. What I did was change it myself and had a co-worker with an obd II code reader reset my light. Enough about all that, here's my question. It's been about 2 weeks and the light is back on. I had co-worker hook up scanner and got code P1158, looked on iequus.com which said, HO2S failed to switch to lean Bank "b". Okay, to those questions now. Which is bank B? The ones I have replaced are the two closest to the engine. Is bank B one of the ones closer to the tail pipe? Also, would this cause the vehicle to run rough? Should all four have been changed at once? Could any damage result from not changing them all? And lastly, because o2 sensors simply send to the computer the work that the catalytic converter does. Is it possible that my o2 sensors are fine and it's really a catalytic converter I'm in need of? I really hope you can help. I need to get it inspected soon (nj). I've had this car for 7 of its 9 years and I really love it, but I'll junk it before I go back to the dealership and I've had no luck finding a local garage who will work on it. Everyone seems scared. Nearest Auto logic facilty is @ 170 miles away. So I'm on my own and would appreciate any help you can give me. Thanks again and happy motoring. By the way, her name is LuLu. YOU CAN POST THIS IF YOU WOULD LIKE.
Answer -
Hi Vince,
its rare that Heated 02 sensors fail but not impossible. Having to replace all 4 02 sensors is edging towards the impossible.
LR states:
"The oxygen sensors consist of a titanium metal
sensor surrounded by a gas permeable ceramic
coating. Oxygen in the exhaust gas diffuses through
the ceramic coating on the sensor, and reacts with the
titanium wire altering the resistance of the wire. From
this resistance change the ECM calculates the
amount of oxygen in the exhaust gas. The injected
fuel quantity is then adjusted to achieve the correct
air/fuel ratio, thus reducing the emissions of carbon
monoxide (CO), hydrocarbons (HC),and oxides of
nitrogen (NO 2 ). Two HO2 sensors are fitted, one in
each exhaust downpipe just ahead of the catalyst.
Note that if the wiring to these sensors is crossed, the
vehicle will start and idle correctly until the sensors
reach operating temperature. Then the ECM will read
the signals from them and send one bank of cylinders
very rich and the other very weak. The engine will
misfire, have a rough idle and emit black smoke, with
possible catalyst damage.
In the event of sensor failure, the system will default to
'open loop'. Operation and fuelling will be calculated
using signals from the remaining ECM inputs.
The fault is indicated by illumination of the malfunction
indicator light (MIL). ECM diagnostics also uses HO2
sensors to detect catalyst damage, misfire and fuel
system faults.
North American vehicles have two extra HO2 sensors
mounted one after each catalyst. These are used to
determine whether the catalysts are operating
efficently."
The trouble you appear to be having is within the emission control or fuel system. Both use mostly the same components, H02s included. The real test would be to mount a Testbook diagnostic tool to your engine and try to isolate the problem quickly. It would be a shame to swap out so many parts in an attempt to find the problem, taking up so much of your time and money.
Other components that would need to be tested would be the Throttle Position Sensor, the Engine Control Module, the fuel injectors, the engine coolant temperature sensor, the fuel temperature sensor and the idle air control valve. Of all these, I've seen the Idle Air Control valve and Throttle Position Sensor fail on my Disco.
The 'banks' that are often referred to are the cylinder banks (2 banks of 4 cylinders) left and right. Left bank (A) is 1,3,5,7; right bank (B) is 2,4,6,8.
If your Cat was 'cat-put' (exhaust pun) you'd hear a loud throatie noise every time you accelerated. You'd have a vibration and you could feel it below your feet as you drive.
You'll have to find someone who has a LR testbook to connect your Disco up to. If you're in NJ perhaps you can search the web for a LR club. Someone within the club could have their own Testbook. You can also try to find a 3rd party LR repair shop. Some Euro-mechanics (BMW, MBenz, Volkswagen, Audi) have the diagnostic tools you need to help solve your trouble.
I understand your fustration over dealership charges and what sometimes appears to be part swapping problem resolution techniques. If you have a dealership that is more interested in profit over customer satisfaction, the stress levels increase with each service call.
Since you have done business with Atlantic British before, you should consider buying the Haynes Manual #3016. It covers Disco's Series I from '94 to '98 models. Much less than the LR workshop manuals at over $120.
Best of luck,
JohnMc
NB: Some clubs to consider -
Jersey Land Rover Owner's Club (J-LOC)
E-mail: conradvicky@hotmail.com
R.O.V.E.R.S Land Rover Club
219 Pleasant Vally Ave
Moorestown, NJ 08057
Contact: Tom Bache
Phone: 609-778-3695
E-mail: tbache9248@aol.com
Royal Range Rover Society
409 State Route 17 South
Paramus, NJ 07652
A couple days after writing this I discovered a nasty vacuum leak. Re-connected everything. lulu seems to be running better. Could this have been my proplem /
AnswerHi Vince,
the vacuum pump and hoses are an integral part of the ignition system. I'm glad Lulu is back to normal and I hope it did not cost you very much. Still...followup on those NJ clubs and get to know where you can service your Disco as local as possible and with confidence.
Regards,
JohnMc
