Welcome Dave

This morning we're back to closed loop on Bank 1, with some sensible trims, so I guess I'll just let it do its stuff. Patience is a virtue etc.

Thanks LPGC.

The failed restarts are all on a warm engine, but not all the time.

I just ran the car for 20 odd motorway miles and it threw an open fault on Bank 1. Bank 1 always used to work (ie wiring should be good) prior to fitting the two new Lemark sensors/ exhaust. I suppose there are a few ways to go: 1. Remove the Lemark sensor clean it up as well as the plug make sure there's no contamination (shouldn't be, but you never know) 2. Swap the Lemark sensors and see if the open fault switches sides (but presumably that will require a reset and relearn beforehand) and/or 3. fit my one good/ old sensor to Bank 1 and see what happens.

Does anyone know of an off vehicle test for an O2 sensor, in case I end up having to return it?

Had to do another Nano job today to get it restarted. It's looking as if the TPS voltage settings/ position settings are diverging ie today I didn't do a full reset but forced a 0.63 setting on the TPS, and 30 steps on the IACV. Still didn't sound wonderful at start-up, but better. Maybe I just need to go on a much longer journey to let it learn, it seems that short hops are confusing the hell out of the ECU. I should be getting my 7/32 socket soon, so can try and remove the IACV

Lpgc, I enjoyed the "history suggests" ref

NTC3354 for the o ring

I'll take another look at the MAF, although it was doing fine before, and after cleaning the idle responded by dropping from 675 to 625, so seemed happier at that point. Previously if I disconnected the MAF the engine failed to start. If it is the MAF though,why would that be isolated to the odd restart?

Seems like something temperature related?

Dunno, maybe the O2 sensors are a red herring then.
The car starts fine from cold still, and will run warm/ under load with no problems, albeit idling (at about 625) seems a bit rough, but for example, today I had stopped for a few minutes and couldn't get the car to restart. Turned over no probs, just wouldn't fire up. I had to reset adaptive values and then it restarted (unhappily) and after 10 seconds' rev'ing ran stably again - second time I've had to pull that trick now in the space of 2 weeks, but other than a few times it re-starts normally - there's no obvious pattern to the failed starts, they've all been after short hops of c. 5 miles. Obviously I don't want to be resetting the values, as it puts me back to square 1 again. But something else is influencing the trim at the re-start, if it's not the O2 sensors.
Coolant temp is being recorded at 97-100 degrees in the GEMS ECU, so fine, I'm guessing. Next on my list is probably the IACV, except the M4 bolts seem to have about a 5.6mm head (or 7/32 ?) and I don't have anything to safely remove those for now. Injectors were all tested with identical resistance 6 months ago, plugs and HT leads are all new/ the same, MAF got cleaned (with contact cleaner), IAT sensor got cleaned (although it still reads a bit off - like most of my 21 year old thermistors tbh). I have good sparks on all cylinders. I have no o ring on the MAF sensor, not sure if it really makes a difference, but I'll get one anyway. Then only other thing I did in the background was drain the coolant, flushed the sytem and refilled with red coolant (which was what was there before)
Is this re-starting issue not sounding familiar to anyone?

This may be slightly unrelated, or it may not, but after replacing both 02 sensors for new (Lemark) I have a poor idle. According to Nano, the voltage on the sensors is hopping around ok ie 0-5V, but the trims to the LH bank are predominantly -ve, and for the RH bank are mainly +ve. Should there be a pre-defined relationship between the voltage and the trim - might this indicate one of my sensors is mis-reading? If so, which one? I still have one good one that came off, so could re-fit it, but ideally I would know which Bank to fit to.
I dug out some 6 month old screen shots of the 02 sensors, when the idle was running fine, and it was showing a similar relationship then -ve on the left, while +ve on the right, but obviously a screen shot was just a moment in time. The trim values seemed less extreme though. Also, my ECU is still learning, after a reset about 50 miles ago, but shd that make a difference?

Silencer? ok, let me look !!

Nope - I'm looking for something that can happen when totally stationary... exhaust and rubbers are all replaced, rear shocks are re-tightened, my next theory is that the exhaust valve for the EAS is somehow transmitting it's noise through the bulkhead. If I lift the bonnet it sounds like the release of air brakes as the EAS pump stops - but i wonder how that sounds from inside the cabin. Do any of the cabin ECUs (esp EAS and WABCO) have any component which could generate a knocking sound, like a relay / solenoid etc?

Tnx Bolt, good suggestions. I can remove power from my door amps (High line, but pre DSP) by just turning off my stereo - which I hadn't tried yet, but will do now. Factory sat nav is off, I have pulled out the power plug at the back.
I haven't explored under the LH seat yet, but it also occurred to me that the EAS ECU (possibly the relay) cd be making a sound, and so I could change it out and see what happens

LOL Richard

I have redone the entire exhaust this week - cats/ int/ rear remounted on rubbers etc. Nice and smooth sounding now, but still clunking/ knocking periodically. This should be something electrical as it can do it when stationary. i have disabled the AC so no AC clutch. EAS pump seems normal, and was re-sealed a few months back. Accumulator replaced on ABS recently too. Other than that, what cycles on and off, with some kind of "solid state" solenoid/ valve on the LHS of the vehicle from the odd/ passenger seat area. The sound is like a soft knock of someone's knuckle on abs. Is there anything behind the door cards that would be moving about ?

Tnx Brian, I picked up a set of those Laser plug testers the other day, not used in anger yet. I was wondering if it would be more effective to use them in their coil pairs, rather than left bank/ right bank? Semantics i suppose, I may just buy another 4 and cover all the bases

OK, so no errors on GEMs in Nano. I completely replaced the exhaust system yesterday, and one of the o2 sensors was corroded in, so I'll be looking to replace that. I think the sensor was functioning ok beforehand though. I think the problem is that the air intake temp now reads anything from 1 to 8 degrees, and so at the restart (when the engine bay is now warm) the calculated fuel air mix is now wrong. I optimistically sprayed contact cleaner at the IAT sensor in the meantime - a new one's the better part of 100 quid

Tnx for the tip George. No Brian, no gas...that would just give me another thing to fix. I'll get it on the nano this weekend.

Chris/ Sloth, thanks for the suggestions, I'll check them out

V8 starts on the nose,and idles fine, from cold. A couple of times the other day i "had fun" restarting when I'd just stopped for 5-10 minutes. Engine turned over no problem, but didn't fire up. After a few attempts it just about caught, and I had to keep it rev'd to 1500 for 15-20 secs for it to stop choking. As soon as I had it under load ie in reverse or 1st then it could idle at 650 again.

Does anyone recognise the symptoms?

I haven't yet cleaned up the IACV since i bought it, or fitted a new fuel filter, and i will shortly change the exhaust down-pipes and so clean the oxygen sensors at the same time. MAFs clean, injectors are ok, spark plugs and HT leads are new

Bolt, perhaps also consider the front too eg inlet manifold - a leak will run over the inlet manifold gasket, under the manifold itself, and drip down the back of the engine.But if you don't have dried coolant on the composite gasket then that probably ain't it. Also, if you extend the overflow tubing on the expansion tank down to axle level you will be able to tell if there is really a leak, or the coolant is being forcefully ejected

yep, good point about the rivets, I heard that too, might even deploy some of my green Loctite on them, definitely can't be bothered grinding the heads off and putting bolts in etc That said I'm getting no noises at any kind of speed/ over speed bumps etc, so I don't think this is it.
The centre section of my exhaust doesn't have a hanger on it (blame the PO,, or it may just have rusted off), and although the exhaust looks very solid then I guess it means the whole weight of my exhaust is balanced between the exhaust manifolds, and the four or so hangers on the rear silencer boxes. My exhaust is a bit of a patchwork quilt - might be an excuse to replace the whole thing front to back

Ah well, I hope mine's easier to find than that.... retorqued the shocks today, put another few lb ft on them, but as if the car sensed my anticipation as soon as I cycled the ignition on/ off it gave me a little knock. The shocks are completely new / have run for less than 1k miles. I'll test your exhaust theory next Richard, it seems fairly solid, but I'll perhaps put a rubber piece on the panhard rod to see if that makes it go away. tbh, I hoped someone was going to say that there's a little known widget under the rear seat that taps on the body powered by RL xx and de-programmable in the BECM …. no such luck then