Right, my turn to ask a question... and figured I'd post up here before the 'other place'...

2001, 4.6 Thor engine - petrol and LPG.
If I start it from cold, it runs fine - idles about 1200rpm for 20-30 seconds and then idle drops back to about 1000rpm, and then down to normal (seems to be normal behaviour for the Motronic 'cold start' strategy or that's what the manual said anyway! <br>

My problem is if I then hot start it - say go to the supermarket, and come back 10-15min later. Did it today and it had sat for 5min... It will start fine, and idle for a few seconds and then go lumpy and misfire for about 30-45 seconds (I presume until it goes back into closed loop). Then once it's had it's little tantrum, it will run, and idle sweetly on both petrol and gas. <br>

A brief run down of the engine/what I've done to it over the last few years since I've had it: <br>
First bought it and has misfiring at idle - all the time, petrol and gas. Changed TPS, CKS, HT leads and eventually tracked it down to a faulty MAF sensor. Replaced it with aftermarket and problem solved.. ish. <br>
It then ran fine, but every now and again I'd read the codes and the fuel trims would be jammed to max, I could reset adaptives and it would all be fine but over time would get skewed again. Ended up buying a genuine Bosch MAF and replacing the aftermarket Bearmach one - and problem solved. MAF is now about 2yrs old. <br>
Been poking about with the LPG and injectors/plumbing and all that so ran it on Petrol for a fair amount of time and trims seemed pretty stable, no recurring faults in the ECU. <br>
Over last 6 months or so (bearing in mind I'm away a lot and it doesn't get used - so 6 months is probably 1000 miles tops) it's been doing this when restarting the vehicle hot. <br>
Things that have been replaced in the last few years: <br>
MAF (Bearmach aftermarket, and then genuine Bosch circa 2014) <br>
TPS (aftermarket - 2012) <br>
CKS (Genuine LR - 2012) <br>
Spark Plugs (Changed at regular service Jan 2012 when I bought it, and then circa 2014 I changed them for NGK BPR6ES) <br>
HT Leads (Changed first in 2012 as regular service item, then circa 2014 I changed them for Magnecore KV85 HT Leads) <br>
Coil Packs (Changed circa 2104 with Magnecores and NGK's - Genuine Bosch replacement units) <br>
O2 sensors (Changed 2015 for Genuine Bosch sensors - partly preventative maintenance and partly due to LPG system being tapped into them and I was getting the odd O2 signal missing error in the engine ECU - LPG system had been connected on the sensor wiring side and on one side was just 'twisted and taped' so decided it was worth just replacing them!) <br>
IACV has previously been cleaned but it doesn't coke up like the GEMS one does either. <br>

My current thoughts... <br>
I have another genuine Bosch MAF so thinking about swapping that just to rule it in/out. I don't think it's the MAF as the symptoms of my problems before were bad idle all the time, not just on a hot start. <br>
I haven't yet chopped the O2 sensor wires off that feed the LPG system... now I know they aren't needed for anything the plan is to disconnect them altogether. I don't know if the LPG system is somehow interfering with it - but it feels like the problem is in the 'open loop' fuelling before it switches over to closed loop. <br>
I've looked at live data on Nanocom and the MAF reading looks to be fairly normal - however very quickly after I had reset adaptive values, the 'idle trim' fuel trims had shot from the reset value of 0.00 back up to about 1,46 where they were before. Other fuel trims are looking pretty close to 1.00 <br>
I don't think it's likely to be plugs, leads, coils - and as such haven't yet pulled the plugs out to check them - but if people think it's worth doing, then I'll do that in the next couple of days. <br>
I haven't tested fuel pressure - but I don't think it's the in tank pump as it has no trouble starting, and after it hits closed loop, it runs sweetly. <br>

Any ideas/thoughts/things to try? I've had the upper plenum off a few times when doing the LPG bits - and have resused the tin gasket a couple of times - but it's always been cleaned off and then re-sealed with a thin smear of black RTV. What's best to use if I want to spray something around the inlet to see if there is a vacuum leak into the manifold, post MAF? Easy start or something like that? <br>

I've decided I want to get it sorted this month as I have some time at home and want to catch up on some of the maintenance on it, even though it hasn't done a lot of mileage, but I'm likely to be using it more and it pisses me off when I'm out and about to have it idling so rough when I start it up - even if it is only for a short period of time! <br>

Cheers, <br>
Marty

What does the Nano say you O2 sensors are doing when it is running rough? Are they switch or hard over one way, I would suspect rich. The other thing you could try is disconnecting the purge filter solenoid valve. Every so often mine will run really rough on initial start with it either idling very low or not at all and I have to keep a bit of throttle on to stop it from dying. I can either ignore it al let it settle down or switch off and restart when it is fine. The way it runs feels like a really rich mixture but as I'm on a single point LPG system I'm already on gas at that point so my theory is that the purge valve opens and I've got petrol, or at least petrol vapour, going in there as well as gas.

Hi Marty
I have a veteran single-point gas system with its own O2 sensor so can't make any direct comparisons, but I've noticed that the petrol side of the system still reacts and tries to adjust trims (short and long) when I'm running on lpg. As I start and run almost exclusively on lpg (when it works!), if I switch to petrol it's a bit all over the place until it gets used to its new diet.
Anyway, as I said, not relevant to yours.
Have you run the Nano on it to record what's happening when you hot start it to confirm your suspicions around closed/ open loop running?
What about fuel temp sensor- any funnies there?
As far as looking for air leaks post MAF, Easy Start, brake cleaner, ether, in fact anything volatile will do. Usual eggy sucky caveats around stuff like that and stray sparks if you're fond of your facial hair!
Happy hunting...

Beaten to the reply by Gilbertd again!

Right,

Finally got around to having a look back at this after a day of trying to play catch up on door latch and BECM questions and enquiries...

First - Sorry about the formatting in the original post, I need to go through and add BR tags to everything where I typed it out as having a new line, so it's not as much of a jumble.

Second... Thanks for the replies thus far. I did get some live data on when it happened the other day, but I was recording the fuel trims rather than the O2 sensors. Today, I deliberately took it for a trip to the supermarket (only a couple of mins drive, but figured instead of walking like I usually do, I'd see if it did it on such a short trip and record the O2 settings on both journeys.

So - The startup from cold at home, short drive to supermarket, and shut off. O2 values are in this file:
Cold startup and drive

I think was out of the vehicle for probably 10 minutes, and then recorded the startup again. It did it again, and a couple of the misfires almost made it feel like it was going to stall... It started OK - Idled at it's normal 1K rpm for a 10 sec or so (which again is apparently normal on the Thor models) and then it settled down to normal idle speed, and then started acting up. About 20-30 seconds later, with like the flick of a switch it started idling properly again and smooth all the way home. When I pulled up at the house, it was idling at proper speed, no sign of a misfire.

Incidentally, there were no misfire codes logged in the engine ECU - there was only codes for mixture adaptations out of range 'fault occured 1 times, not currently present'.

The O2 live data from the hot start and run back home is below:
Hot restart and drive

Sadly there is no other engine data apart from the O2 sensors, as the nanocom only seems to record what's in the current page of inputs, not a full spread of everything, which would be a bit more useful in this case.

I can add the file I did the other day with the MAF level and fuel trims etc. but it doesn't have O2 data and was from a slightly longer journey, but the startup symptoms are the same.

I don't think it's LPG related as the journey I did today, I switched the LPG off so it was just running on petrol, and the previous time it did it, I reset the adaptive values (in case the LPG had been affecting it) and then did the journey on petrol aswell - and it still did it on hot restart.

Thanks Richard for the idea on the purge valve - I will look into this tomorrow.

Let me know if you see anything obvious in the log files - I'm about to have a thorough look through them myself as I've only just had the time to get them off the Nanocom and convert from CSV to Excel sheets.

Cheers again,

Marty

EDIT: Have reformatted the original post. Also to add, my LPG system is Zavoli Alisei multipoint, with Hana 2002 Gold injectors.

Not sure what the time interval is between each line on the sheet but both lambdas are reading rich until line 85 (with bank 1 showing leaner than bank 2 all the time) and they don't start to switch between full lean and full rich until line 109. That suggests to me that for some reason it is running rich initially for some reason.

I am also not sure the time division the nanocom records at, but I presume it's 1sec intervals.

Something had to be causing it to run rich though, as I reset the adaptive the previous time I, and recorded the fuel trims, and it was evident to see the idle trim very quickly making its way from 0.00 which was is default value, back up to about 1.46.

Also just noticed that the O2 heater status changes from ON to OFF very quickly for the period it was misfiring. And at that point the lambda output ( rather than the raw O2 voltage is showing 0 74, where I would have thought it should have been closer to 1, which is what it switches to as soon as it evens out....

I don't know if the O2 heater switching is a cause, or an effect that is happening because of something else. I'm planning on checking the O2 heater grounds just to be sure... also, shouldn't the heaters switch off when they are up to temp?

Maybe it wasn't running long enough so I didn't get it to that point.

Might be completely irrelevant but on your cold start graph Lambda A Output starts to vary at line 79 but Lambda B Output does not vary until line 228. Perhaps a contaminated sensor or a flaky heater?

Didn't get a chance to look at this any more today as I was building a door latch for someone who wanted one ASAP and have another one to do tomorrow...

However, I did wonder about the heater - but the annoying thing is that the sensors aren't that old, and I bought genuine Bosch ones rather than cheap aftermarket.

If it is fine tomorrow, then I'm going to try and crawl under it and snip the wires to the LPG system where it's tapped in (I moved them to the vehicle loom side, rather than the sensor-side as they were previously) - but now I know the LPG system doesn't need them (in fact I've disabled them in the software) I'll cut the wires and see if that makes a difference.

Whilst I'm there, I'll check the connectors and make sure they are in good condition and making good contact. I'll also check the resistance of the heater circuits in the sensors to see if there is any variation between them...

Then I've got a sheet of metal to cut for my DSP amp modification, and a list of other things to work on again!

I'll update tomorrow if I get the chance to look into it, but something tells me it is something O2 sensor related...

Fixed it... I think

Finally had time to crawl under it today and take a poke about. Have cut the wires from the sensor feeds and taped them up and tucked the LPG loom bits behind the heat shields, so that's all disconnected now.

Pulled the O2 sensor plugs apart and on RH side (bank 2) found that one of the heater pins looked a bit worse for wear, and upon popping it out of the housing, found it was almost corroded through and was about to snap (on the vehicle loom side, not the sensor).

So having no replacement pins, I did a nasty crimp connector on it and then pulled the same dodgy pin from the sensor side and put a crimp connector on that too, joined them up and then heatshrink over the top. was going to solder/heatshrink, but the sensor side wiring must not be copper (I presume to do with the heat) as it wouldn't take solder to it - so crimps it was.

Checked the LH side (bank 1) and they were a bit dirty but all ok otherwise - so cleaned them up and back together.

The verdict - Took it out for a spin and on hot restart, no misfiring or lumpiness - just starts up, idles about 1000rpm for a bit, drops to normal and then behaves itself. Reset the adaptive values on Nanocom to see if the idle trim still goes way out like before, but the main symptoms of the problem before are gone.

Now I just need to find out what type of connectors the Bosch O2s have on them and see about replacing both vehicle and sensor side connectors at least on Bank 2... For completely sealed connectors though, I wasn't impressed at the amount of dust and crud there was in both banks!

Thanks for the ideas and pointers... after looking at the live O2 data myself, I kinda concluded it was something to do with the sensors, but nice to have the extra sets of eyes on the problem!!

Cheers,
Marty

Martyuk wrote: was going to solder/heatshrink, but the sensor side wiring must not be copper (I presume to do with the heat) as it wouldn't take solder to it - so crimps it was.

No it isn't, they are stainless steel. You can solder to them but you need a very hot soldering iron. I've got a mains one that won't admit to what the wattage is but the longer you leave it on the hotter it gets. After half an hour you can damn near braze with it, that did it but I've used crimps instead before. Proper W crimp ones though not these horrible squash flat things.

I figured it was probably stainless..

Well, the bad news is that something is buggered up with it now as I've just got back from dropping the missus off at the train station and its idling stupidly rich now. Looked at live data and no 0.00V reading from both O2 sensors - even after they've been running awhile. Guess I'll be crawling back under there soon to see what's going on... I reset the adaptive values after fixing the heater wire problem, and it seemed to run fine yesterday.

I knew it would be too easy!

So, got back underneath it and had the lightbulb moment that maybe the LPG install for whatever reason cut the sensor feeds and they were reconnected down the wires they had to the sensors (Since they were the wires I cut yesterday and it mysteriously didn't work after!) so went back under and re-soldered/heatsrhink on those feed wires.

Put the Nanocom on it and checked live Data and bingo, feed from both the O2 sensors... fixed... or so I thought.. started driving and part way down the road as everything warmed up a bit and then suddenly felt it idling rough again, and found the sensor values again reading back 0.00 V on bank 1 and 0.10V on bank 2. Didn't even attempt to flip-flop, and it started to run stinking rich again.

Thoughts? Break in a wire, duff sensors? I still have the old sensors that I can put back in if needed or do I first take the punt and cut the connectors out altogether and join all the wires directly in case the other pins in the connectors are on the way out? Getting sick of it idling so badly, as usually it purrs like a big V8 kitten...

The lambda feed to the LPG system should just be Tee'd into the signal wire from the sensors so shouldn't have broken the path at all. It's only so that the LPG diagnostic can display the lambda voltage to save you having to have an OBD reader connected as well as the LPG software. Might be worth hanging a meter on the lambda signal wires at the ECU to prove that the Nano isn't telling fibs.

That's what I thought aswell - but hey, they are reconnected now and I can view them on the LPG software, and fired it up to see what happened. They had obviously cooled down a fair bit as they were both starting from about .45V and then bank 1 (which is actually my Bank 2 on the vehicle as it's all wired back to front - the injectors are aswell, so I noticed!) started to flip-flop, but bank 2 (RHS then slowly started to drop and settled at 0.01V.

The Bank 1 reading on the LPG software continued to flip-flop, but I presume that too would have eventually dropped - given that's what happened to both of them whilst I was out. Seems strange that they seem to be fine when cold, but when it warms up they both went to 0V - which to the ECU - it thinks it's just running stupidly lean, so it's dumping a load more fuel in to the point I could smell unburnt LPG in the exhaust.

I'm half tempted to swap the sensors back to the old ones - but will pull the ECU out of the housing tomorrow and see what signal is getting to it. I think if I have to go out over the weekend and I can get it sorted, then I'll be pulling the sensors totally and letting it run open loop - got to be easier on it than running that rich!

Right - this is starting to hack me off now.<br>

Been back under there and cut out the factory connectors and crimped the wires together. Got pissed off at the crimps as obviously the lot of cheap ones on ebay were just that - cheap shite as half of them didn't crimp properly and took at least 2 goes to get a solid connection.<br>

Just been out and taken it for a drive and recorded the O2 sensors. I missed the bit before I drove off as I was watching it on live data, but as you can see the heater status is now good (I get 12V to each sensor heater wire) but the output from both sensors is just strange. Both holding close on 0V which of course makes it think it's running lean, and is pretty much dumping raw fuel out the exhaust at idle.. the thing stinks.<br>

So, ideas on what would make the sensors run for about 30 seconds and then just show lean running the whole time? unless the heater elements in both sensors are failing when they get hot, even though the ECU thinks it's driving them - but I'm sure there is a fault code for that, which it's not showing. Besides, they were working OK before - just took longer to warm up, I think because of the dodgy connection on Bank2

My current theories: <br>
1) Both sensors have somehow failed - I've eliminated the connectors (have some new standard econoseal ones on order so I can put connectors back in again) but maybe somehow I've killed them when rewiring - though the 12V feed to the heater has always been off (ignition off) whilst I've been under there working<br>
2) Wiring fault - somewhere in the loom there's a break, which has happened when I've been doing the rewiring - though that doesn't explain to me a) why both sensors fail, or b) why they are going to 0V - I was under the impression that if there was a wiring break then it would default back to 0.45V c)if there was a short in the wiring, then why does it work for 30 or so seconds and then plummet?<br>
3) ECU fault - I wonder if something has unintentionally shorted whilst I've been under there and it's cause the input side of the ECU to go pop. Again, doesn't explain why it reads normal to start with and then fails. Unless the heater grounds are joined in the ECU somewhere and the driver for those has gone pop when I was doing the wiring to the first one. But again, power to the heater circuit was off when I was doing the work on it.<br>

I have a spare ECU, so tempted to bung that in and sync it up and then see what the deal is. If it's still there, then I can eliminate all of that nonsense and concentrate on wires and sensors.<br>

I have my old sensors still, so when the connectors arrive, I might look at refitting them (as I don't think there was anything wrong with them, they were replaced as preventative maintenance with genuine Bosch sensors). That will then either rule in/out the sensors and then it would only leave the wiring, which I am planning on pulling back topside when I crimp the new connectors on, so will do a continuity test on them back to the ECU pins whilst it's all accessible.<br>

Any other thoughts?<br>
<br>
Marty<br>
<br>
Latest O2 live data: O2 Data, crimped wires

Swapped the ECU, and no change.

Has to be wiring or sensor now. Will have to wait until connectors arrive and then I'll chop the crimps and pull that part of the loom up top and test it all and put new connectors on. Will also pull sensors out and see the state of them, and most likely put the connectors on the old sensors and bung them back in to see if that makes a difference.

Hi Marty. I've been pondering this all afternoon and kept ending up at sensors. Can you just confirm that you're only testing and faultfinding on petrol now? I've got a bit lost.
I'm no expert on the sequential lpg side- never even seen one in the flesh- so can't really help there, but experienced similar baffling outputs on the petrol side on my GEMS idling ultra rich when one sensor failed and I found that the PO had kludged the wiring so that left sensor was feeding right bank and v.v. Out of interest what does it run like when held on open loop after an adaptive reset?

Howdy...

Yes, ONLY testing on petrol.. the bit about LPG up above was just because my logic went 'I cut a couple of wires and now have no output, so I should probably try reconnecting them' But as Gilbertd mentioned - the O2 sensor feeds go back to the LPG ECU just as a visual monitoring of what the sensors are showing in the software. I left them disconnected again today when I cut the connectors out.

The problem has ONLY been there since I got under there and been fiddling with it.. well, fixing the original problem with the heater wire on bank 2 as that was the reason it was misfiring badly on a hot restart. That is cured now - it just runs like shit all the time on idle now!

The latest test shows that BOTH O2 sensors now drop and show a voltage of near enough 0V, which I gather on the later Thor systems is ultra-lean - which makes sense as you can just about get high off the petrol fumes coming out the exhaust now as it's running that rich!

I haven't tried holding it in open loop and resetting the adaptives yet - I have to go to Newbury tomorrow to go and look at a BECM for an owner, so it'll get about a 60mile round trip. My plan is to cut the sensor feed wires so it will do it all in open loop, as to me that has to be better then closed loop but constantly thinking it's running lean and overfuelling. So I'll be able to answer that question properly tomorrow...

But I did reset the adaptive values whilst it was running closed loop and the sensors were still messed up and before it started adjusting itself again, it was running pretty smoothly at idle.

I think it is probably the sensors aswell - I just don't understand how me fixing the heater problem has caused both of them to fail. I only did one pin at a time, so I know I haven't got any of the wires mixed up!

My only other thought is could it be that the sensors are coked up now and there isn't enough exhaust air getting into the sensor itself? I'm already planning on pulling the sensors back out, but any ideas on if they are cleanable?

Marty

If truly coked, they're not really cleanable. If they look like they're bunged up with soft soot, a bath in petrol, followed by a hit from the air line might shift it. How about hitting them with a propane torch or something and measuring the resistance across them on the bench? If for some obscure reason they're failing after a short period, you'd pick that up on the bench test. Law of probabilities of 2 sensors failing in exactly the same way at the same time must be up there with a lottery jackpot win though!