I've just bought a new pair... Found genuine Bosch ones on eBay for £30 each with free shipping so thought sod it.

I wonder if I probed the wrong pins and killed them - apparently you can kill them if you try to measure the resistance with a DVOM - unless it's more that 10 MOhm impedance on the multimeter inputs (will have to check mine now)... Still doesn't explain why they are OK for a little while and then stop... I was trying to probe out the heater wires to make sure they were both intact (they are, about 3.5 ohm resistance on the heaters)

I've also read that they 'breathe' through the wires to compare the external oxygen to the exhaust gas oxygen. I'm just wondering if I've somehow blocked them up...

Either way - A new set of connectors and new sensors and fingers crossed it sorts it. I don't like just throwing money at a problem, but they aren't something that is repairable if they have decided to take dive. Still, if it gets it running happily again, then I'll be happy... I'll just have to sell a couple more door locks or something to cover it... haha..

Will report in a couple of days when new sensors are here and installed.. I think for tomorrow though, I am going to snip the signal wires and let it run open loop. It has to be better than how it is at the moment!

Marty

I gave you a bad steer earlier. It's the Titania (GEMS) sensors that vary resistance based on O2 content. You've got Zirconium. You're right about reference air. Here's a link to an "everything you wanted to know" about your sensors (well, the NTK version anyway)! https://www.ngk.de/en/products-technologies/lambda-sensors/lambda-sensor-technologies/zirconium-dioxide-lambda-sensor/

and with a Zirconia sensor you don't get a change in resistance, they generate the output voltage. The change from Titania was partly to make it easier to fall into line with the OBD2 standard which assumes 0-1V sensors (compared with the 5-0V from a Titania) and probably as a cost saving exercise (as they are a lot cheaper). Downside is that Titania don't need a hole for reference air so aren't affected by being dunked in water when wading whereas Zirconia aren't very happy with being submerged. If you've been thrashing down your lane to get to the garage, you could have killed them by filling them up with water (I know I've still got muddy water stains on the underside of my bonnet (and everywhere downwards of there) on mine from following you down there).

Well, the underside is properly caked in mud - a fair bit I tried to jetwash off, but still so much remains... It's a natural rust inhibitor now it's all dry isn't it?

I still think I've damaged the sensors somehow whilst I was under there, or I've blocked them up - but I've had enough pissing about with it so going to re-crimp the original connectors to the vehicle loom as I managed to find some pins for them - and then I'll swap the new sensors on when they arrive and be done with it.

I went under it today and cut the sensor feeds to the ECU before I went out today as had about 70miles to do and didn't really want to do that with it running stinking rich, so figured open loop the whole time was going to be closer!

The good news... she ran really well today in open loop - idled nicely and started up strong from hot again, which it wasn't doing before this whole saga started - so I'm now confident that swapping the sensors over when they arrive will sort the problem out. And then I can move onto the next one!

I'll have a look at the Zirconia link you pasted above... always interested to see how things work!

Cheers,
Marty

I don't think UK dried mud is a natural rust inhibitor. Maybe it's different from NZ mud?! I've found that when restoring old Brit stuff it's the bits where dirt has stuck in pockets that corrode faster. The dirt acts as a kind of poultice, keeping the environment warm and slightly damp and holds salts etc against the metal.
If your sensors were killed by either thermal shock or drowning, maybe while you're under there you could knock up a quick shield for them? A bit of curved stainless and an exhaust clamp would make a passable deflector. I'd have thought that there would be a lot more noise on the forums if this is a common issue on P38s though so maybe it's something else that's killed them.
Good that the problem's sorted on open loop anyway. Means that a fix is only a Postman away!

I was fairly tongue in cheek about the mud being an inhibitor... it's my lame excuse for not getting under there and giving it a proper clean... I do need to get in along the sills where it's all totally caked and get all the muck out as I don't really want it corroding out on me...

I am pretty sure that I've killed the sensors when I probed them, or I've blocked off the natural air flow into the sensors when I've joined the wiring so the comparison inside is way off or something like that. The sensors were working before I got to them - just the heater wire was causing the previous problems as they weren't heating up (well bank 2) fast enough on a hot start. I am guessing that was masked on the cold start as the engine ECU holds it at slightly higher revs for a bit so it was above the normal idle speed where the problems were occuring.

Still, it will all be sorted soon.. And maybe whilst I'm under there I'll transfer some of the clumps of dirt and mud from the chassis to the road :)

My next one is going to be taking the trim off the top of the windscreen and checking my front sunroof drains, as I found a puddle of fresh water on the drivers side mat and just above the headlining at the front by the windscreen on the drivers side has some moisture there... Fairly sure (but I'll check anyway) that it's not pollen filter housings as I've had them apart already and re sealed them all with silicone when I put them back together..

Take one thing off the list and put 2 more back on some days!!

Hi Marty, ive had the same problem all winter with water on drivers floor mat and coming down windscreen pillar tried allsorts to fix it but in the end I took the trim off both door pillars outside and trim off top of screen and sealed screen to car with (geocel trade mate roofers seal). it even seals when its raining. I did it a month ago and not had a leak since I did it (it no longer drips on my knee ) result..i thought it was roof but it was windscreen seal. hope that helps.. cheers Steve

That's great to hear Steve, thanks for that.

I have a feeling it is along the top of the windscreen as I can see parts where it almost looks like its got inbetween the laminated layers of the glass..
I think I used bathroom silicone sealant on the pollen filter housings, but want something super duty (and black preferrably!) for the top of the windscreen area, so will have a look in screwfix and toolstation for the stuff you used as if it does the job, then it's good enough for me!

It can't hurt for me to check the sunroof drains aswell whilst I'm there...

Cheers,
Marty

Tiger Seal.......

Well, I finally got time to install the sensors this afternoon. Re-crimped new pins onto the vehicle side of the loom, cleaned out the connectors and refitted them to the loom.

Installed new sensors, plugged it all up - and happy to report that everything is back to normal.. Switching O2 sensors all the time, normal idle - not trying to stall itself or any nonsense like that.

Got some Geocell black sealant and did across the top of the windscreen aswell, so just have the front sunroof drains to check, and then that's my mini-list checked off for the moment. Next job is to find out where my coolant leak is at the rear of the engine on the drivers side. Can see it running down over the starter motor, but typically can't see anything above that from below, and the manifold heat shields are in the way from the top... I'm going to try giving the hose clamps on the heater hoses a nip up on that side as they are kind of above the area.

Anyone (gilbertd) who's had the engine out and seen what else is around that area where coolant could leak? I can only think of head gasket (if it's leaking externally) or core plug leaking, if it isn't a heater hose join..

Marty

If it isn't a hose, then a slight leak from the valley gasket would be my next choice. There's waterways through the inlet manifold into the heads at both ends and torquing the bolts up at the back is awkward so I bet they often don't get the same torque as the others. The only core plugs at the back of the engine are behind the flywheel so inside the bellhousing so any leak would drip out the bottom of that rather than run down the outside.

That's good news then... Well, ish... I had a mate back in NZ who had one let a core plug go and it was an engine out job to replace them (as no point only doing the one if the rest are the same age!!)

I did wonder about valley gasket, and had been toying with the idea of changing it as I am sure it leaks a bit of oil out the back of it too but I also keep planning on pulling the engine from my other Thor 4.6 so I can strip and rebuild it, and thus swap a fresh one in ... maybe over summer... sure as shit ain't going to happen before I go away for work!

It's definitely not dripping out the bellhousing (it does end up on the bellhousing at the bottom by the little notch out which I presume is to let any leakage out), as I can see it on the bottom of the starter motor where it's run around the side of it.