Contour Enthusiasts Group Archives Forums General Troubleshooting EEC IV code 176; O2 sensor not switching. Q's....

Hiya,

I tried to post this earlier, but it seemed to have vanished... oh well, I'll try again.

I've had an intermittent CEL on my 'tour (95 2.5L) for a long while. It comes on every 3-5 minutes while cruising at highway speeds, stays on for about 15 seconds, and then goes out. It never lights when driving around town (which is most of the time).

I read the codes on it this evening... got no hard faults, and error code 176 from memory. (I had gone for a highway cruise and the CEL had lit a couple times just before I checked the codes).

From the Dali Design page, it says code 176 is:
Oxygen sensor not switching - system is or was lean Left or Front HO2S Fuel Control.

I also did the diagnostic run engine test, and it came up roses... code 111, all is well.

So, I take it this is the O2 sensor on the front, right above the cat? Is it a common failure mode that it would get wonky intermittently (maybe when hot, on highway?) and appear OK in stop and go driving? (and also appear to be OK - no hard faults or CEL, 5 minutes later) Seems kinda fishy to me.

Do you think there's any use playing with the connector to the sensor, or would you just replace sensor?

Thanks for your thoughts...

Brent

the problem might be a vacume leak. since the light only comes on when crusing under load and not when idling or being revd with no load,
you can test the sensor to see if it is good by driveing the car for ten minutes then park the car,
open th air box,
conect a volt meter+ to the output wire of the sensor and the - to ground,
then start the car and rev it to1600 rpm for one minute then with it idling spray a small amount of carb cleaner in to the maf
the voltage should jump to .9v or 1.0volts if it does the sensor is good if the voltage doesint get above .5v then its a bad sensor ,
if it is good i wold change your intake gaskets

so how would one diagnose where a vacuum leak is? There are several gaskets on the intake side, aren't there? Upper, lower , plenum... (or does plenum gasket = the "lower" ?) Seems I'd better buy a manual.

I had the plenum and EGR gaskets replaced about 14 months ago. (dealership had diagnosed a vacuum leak)... I would be not at all surprised if this ends up being the same problem... maybe a different gasket that wasn't replaced had a leak, but maybe sealed (for a while) just from taking the intake apart and reassembling.

Car seems to be down on power a bit too (but runs smooth)... but after a while it's hard to tell if that's real or just perception.

Brent

the best way is to use propane or carb cleaner,start the car let it idle and spray in small amounts around the intake manifold where the gaskets are if the idle changes (slows down or revs up)that is where the vacume leak is.
but you might not find one because your light only comes on when crusing under load not at idle,thats why i siggested checking the sensor.

If it had an air leak at idle, could it be that the circuit controlling the idle air could compensate for the leak and make it would idle OK with no CEL? If so, maybe I'll be able to detect a leak by spraying at idle.

hmmm... thanks for the help.

Brent

Hey guys i am having the same problem with my 95 se mtx with only 85k on it. The mechainc checked for vacuum leaks and found nothing. The o2 senors are new as well with about 7k on them , put i a few months back.

He told him about the injectors and he said it might be a possiblity but he can't check them withthe scanner becasue my car is OBD1.

Another thing is mentioned i s maybe a lazy o2 sensor?>

Any comments or suggestions?

I'm 99.99% sure it is just a O2 sensor going bad.

Replace it and you won't see it again... until the next one goes bad

-Lance

or me???

Brent

I agree with the front O2 sensor theory... Cruising at highway speeds requires a lot of fast switching for the sensor which it can't perform.