WAAAAAY off topic -but curious

[Dan Filetti]

So, a buddy of mine bought a used Land Rover with +/- 100K miles on it.... -I know, I know it's a love it or hate it kind of thing, and he's a brave soul...  anywho, it was running like a top (and still is) for the first few thousand miles around town with no issues.  So he takes it for a trek out to Pittsburgh (Dean Hess country) from our area (+/- Philadelphia)  -PA is a wide state and half way there, the check engine light comes on.

It continues to run well so he finishes his trip and takes it to a specialty place to have it looked at when he get's back.  Now HERE is where it get's interesting...  The shop guy says 2 of the 4 O2 sensors are bad and need replacing @ $500 per -and oh, by the way you should do all 4 while you're at it....  Further he's told that aftermarket units fail quickly so are not worth it...

He declines to have the work done, (he only paid like $3500 for the vehicle in the first place) and he wanted to check out prices etc.  So it's still running well, so he drags his feet in pursuing a fix, and drives around for a week or so with the check engine light on. 

Today he calls me and tells the check engine light has gone off!!!   I'm thinking it may be related to highway vs. city driving but not sure.  (the other possibility is it's completely random

Any how, I'm not even sure how these things work, or if they can 'cure' themselves or if it is even plausible that city driving could 'cure' an issue with an (or 2) O2 sensor(s).  But I thought I'd throw these questions out here: 

What are the chances it's all good now? 

Anyone have luck/ issues with aftermarket O2 sensors? 

Are they fairly universal or more application specific?  (AKA: should he be able to pull one off of a fuel injected... whatever and make it fit/ stuff it in?)

Anyone have any other ideas what may be going on?

Just thought I'd ask,

Thanks,

Dan

[rktmanfj]

No Land Rover experience at all here, Dan, but the 'check engine' light on my old E150 comes and goes all the time.

It kinda freaked me out at first, but the manual says that's normal.   

Randy T
Indy

[tqmx1]

One thing it might be is overfilling the gas tank. We have had a couple of Fords (96 SHO & 99 Sable) that when you would pack the tank some raw fuel would get into the evap systen and would take about 4or5 hot to cold cycles to clear the code.

[freespiriteng]

I am not a mechanic on these new things, give me the old points, non computer and natural machines and I am fine. I presently have an O2 sensor bad on my S-10.  When it was cold outside it seemed to work or at least the engine light didn't come on.  Now it trips the light all the time.  My mechanic prefers the factory sensors but also said that the aftermarket (Oreilly's) are fine but on the computer don't react as fast.  He didn't care which one I put in.  The factory one was $169.00, the aftermarket $69.00.  Guess which one is going to get used?  The guy is going to replace it for twenty bucks.

My advice is to check around and if needed replace so the light doesn't come on.  That way if the light comes on because of a fuel pump issue or something he isn't stranded somewhere.

Joe

[Fred]

Nothing fixes it self. I suppose it could have been an error in the reading from the sensor or some temporary episode that caused the sensor to read improperly, don't forget it is English after all   As long as the light is off I wouldn't worry. The thing to remember is why that sensor is there. It is there for emmissions, so if it is not working properly you will be spewing more nastys out the tailpipe, if that sort of thing matters to your friend and it won't pass the state inspection. It could also damage other things like the catylitic converter.   My .02, take it for what its worth and if TRoy disagrees believe him

Fred

[the fan]

You did not mention the model, but if its a freelander tell him to sell it now. Hell tell him to trade it in on an 8 year old Hyundai Santa Fe.

My sister in law insisted on a freelander, and my brother spent more money maintaining that P.O.S. than She paid for it. I helped him work on it several times and That thing was very difficult to work on and very poorly made.

[Ratchet_72]

Buy an OBD-II computer on Ehey for $30 and you're golden. 

[Marsh White]

Bosch makes a great aftermarket O2 sensor.  I don't know all of the model differences, but they shouldn't cost over $60ish dollars each.  The O2 sensor should be located in the exhaust manifold.  You should be able to get to them by crawling under the car and reaching up.  They are kinda like spark plugs...just unscrew the old one and screw in the new one.  They can be a be a bit of a pain in the ass to unscrew because of heat and rust.  It is normal for a failing O2 sensor to trip the "Check Engine" light intermittently for several months...even a year or more.  If they totally go out, they can cause your engine to run badly.  That's all the risk really...the engine may run like shit...but they can't really hurt anything permanently.  Anyway...he can spend $120 at AutoZone and spend 10 minutes under the car and the job is done.

Disclaimer: I am not a mechanic...just a webdesigner.  Although I have probably spent more time under a car than any other webdesigner...FWIW

[TRoy]

..next time include the vehicle info and specific code #'s 

[pdxfj]

If you do end up replacing the O2 sensors yourself, be sure to buy the special O2 sensor socket to fit. 

It'll be the difference between a 10 minute job, and a total PITA.

[rlucas]

If it runs OK, I've found that the judicious application of a piece of electrical tape over the idiot light works wonders.

Rossi

[n8man1068]

Another vote for gas cap/overfilling.
I'd imagine that if any of the o2 sensor are bad, when the check engine light is on it will stutter or have other performance issues. Aside from getting an obdII scanner and checking it himself (handy tools to own) most Advance Auto/Autozone places will scan the codes for free.

[Mark Olson]

Dan, tell your buddy to get scan tool and check for himself if the sensors are bad.
this is a common scare tactic of the auto repair world.
with four sensor systems it is common for them to take a shit at 100k and is recommended by manufacturer to replace all four as a tune up procedure.
aftermarket sensors are ok to use if they are a major brand you recognize, bosch.

with the vehicle computer check light it will throw a code when the sensors are out of range, not necessarily bad sensors or the light will never go off. sometimes pulling a hill or cheap gas, dirty spark plugs, clogged air filter will cause a o2 sensor code.

The difference between town driving and highway is significant if the engine is not reaching normal operation temperature. the computer will not read the sensors until engine is fully warmed up.

hope that helps.   

[Dan Filetti]

Thanks folks, I've passed all of this along.  He was shocked that all of this came from a motorcycle forum -I told him that just the nature of the folks on this list, helpful and knowledgeable. 

Dan

[FJ Flyer]

He can also go to AutoZone and they will scan the codes for free.