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[iansoutham]

Guys, want a second opinion on an issue I am having with an o2 sensor on my X20XEV 1998 Estate.

Last week or so I have randomly had the EML come on soon after starting a drive (about a minute I believe). Car still runs fine, no problems. Turn the car off and back on, even straight away, light goes out and stays out. This can happen cold or hot as well.

Have run Tech 2 on it and the code is P0130. Live data shows the sensor working normally through its range from 11mV upwards. Hard throttle goes open loop, sports mode goes open loop on overrun and high rpm/load. Closed loop at all other times once coolant temp is above threshold.

When the EML is on, the reading is open loop and either 39mV or 11mV (cannot remember which) and is static. This obviously would give the P0130 code as o2 performance is out of spec.

I cannot remember changing the lambda sensor since I got the car in 2012 and it has done probably 50k since. Cat is new last year but as is before sensor should make no difference. No visible or audible leaks from manifold or other but, again, this would give probably a different code if there was a leak.

My question is... is this an internal defect in the Titania lambda sensor (but is weird in the randomness) or wiring (nothing obvious I can see but have not had a chance to disconnect plug, etc..)?

Any thoughts? I am going to look through my collection and see if I have an old sensor from either my X20XEV Cavalier I had or from an older 1994 X20XEV Omega I helped break up a few years ago and may have kept to swap but want to clarify fault before I go spending the best part of £60 on a new TDK lambda sensor.

[Doctor Gollum]

Sounds like the sensor is working correctly

[iansoutham]

I know, which is weird. But, if it was wiring then it would be more often but under certain conditions, ie hitting bump in the road or turning left, etc... ECU issue would be every time, not completely random. Still wondering if internal circuit fault? Thought about iffy fuel (Tesco 95 RON but supplied by Shell at that station which also supplies CostCo round the corner) but have used it all the time, not just a random fill up. It is the drop to a minimum value but resetting with no problem that is baffling me. I have even reset the ignition whilst rolling within 5 seconds of coming on and it goes out straight away.

[iansoutham]

For example, did it after pulling away from dropping something off in postbox yesterday evening (had driven for 20 minutes from work), case on within 1 minute by reset. Driven this morning but nothing on for same 20 minutes route. Turned car off at work, back on and pulled away then parked back up as a test, nothing.

[iansoutham]

Had a thought, does anyone have the values for the pins when hot and cold, might be able to test that way?

[Doctor Gollum]

From your example, what were the coolant temp and rpm/ idle doing?

[iansoutham]

Coolant temp on ecu was 88 degrees (gauge shows 4-6 deg higher). Rpm was low rpm under light load (just pulled away 10 seconds before)

[Doctor Gollum]

That's normal operating temp, so not that. Wondered if it might be that there's a discrepancy with the fuelling, perhaps a slight delay on coming off idle making the mixture go lean?

My 3.2 used to occasionally pop the eml on if left idling for a spell.

Only ever 0420/0430 though, so never worried about it.

[iansoutham]

Okay, able to replicate it again with Tech 2 attached.

After coming on the 1st time (never on initial journey, only secondary after a short parked, engine off delay, basically, once the car is up to closed loop temperature I would suspect) it is coming on after restart at a duration of around 1 minute.

The MAF readings are stable and at around ambient pressure when it happens, the car can be revving or simply at idle. The SAI EGR reading is 0% as well (just in case faulty MAF was involved). I have tested this by starting the car, powering up the Tech 2 and either pressing the throttle lightly with my hand (max 1/4 throttle to imitate usual levels) and just leaving to idle. Exhaust manifold does not show any audible signs of cracking (I have replaced once a few years ago already) and when it has leaked in the past, the ratios did not change that much, certainly still within specs.

I am starting to think that it is heat soak into the sensor? The wiring all looks good and not chaffed or hanging loose. The lambda is just above the pre-cat (running a 2.2 downpipe with pre and main cats) so am thinking maybe old sensor and residual heat? Heating side of the sensor all looks good. Lambda is in a vertical position (upwards from pipe) so no contaminant ingress from say cooling condensation.

[Doctor Gollum]

Certainly sounds feasible.

Warm starts on cars with autochokes were often troublesome for similar reasons 

[Enceladus]

The sensor must be 20 years old if it's never been replaced. These thing have a limited life so it's likely
expired. Since it's upstream of the cats the fault code suggests the sensor is faulty. Or a wiring problem.

However those titania sensors are expensive so I appreciate the reluctance to just replace it. It might also be that it's blocked with carbon build-up, so I'm wondering if it can be cleaned by soaking it in iso propyl alcohol or even petrol or something else? Anyone know?

[iansoutham]

Looking at the sensor, it has been changed at some point in its life (not rusty enough not have been).

When I worked at VX, we used to spray the sensor with brake cleaner and light it for a few seconds to decoke them. Might try it at the weekend but is a pain to get to....

[MikeDundee]

I had the same issue several year ago with the 2.6 v6, not sure if would affect yours , was a common issue EML on all time, or intermittent, car ran fine. Car was left with Marks DTM for a few months while i was away sunning myself, lambda's were repositioned further back from what i recall and never had the problems since, should be a thread somewhere on this. Unless MarksDTM replies    

[iansoutham]

Well, found a spare Zafira A lambda sensor which measures the same values but with a longer wire so have fitted that to see what difference it makes.

All working so far and Tech 2 is showing good values so will run it like this for a couple of days until the new ones rives and, if good, will swap to the new one.

Does seem to back up my theory of heat soak as well as only had car running for leas than a minute and a half and the pre cat was getting too hot to touch whilst trying to hook wiring up out the way.

[iansoutham]

Update..... the replacement lambda sensor has been working fine and no EML yet so have changed for a brand new sensor and all should hopefully be good........0