Disco 2 O2 and fuel trim issues

Right, so I have read a thousand topics on multiple forums about this and I still managed to lose track. I've learned a lot, fixed and tried a lot, but still here I am.

I'll try to explain it logically.

Car: 2000 Discovery 4.0 V8 with LPG and 160 000km.
Bought it with bad CO/lambda so it couldn't pass technical inspection.

Already done: Previous owner changed the coils, HT leads, plugs, MAF sensor and O2 sensors.
I changed the plugs again (one had broken porcelain and the ones on the right were blacckkkkk), the HT leads again (put in the 8mm kind) and the MAF sensor again because it wasn't a Bosch sensor and the engine ran better when I unplugged it.
Exhaust gaskets on the right are new too because I thought I heard something there. Turned out to be nothing.

Issues: In the beginning, it ran great on petrol when cold, horrible below 2000rpm when hot and okay on LPG anytime. Since I changed the MAF sensor by a Bosch one, it runs great on petrol any time and quite bad on LPG when hot (suppose that has something to do with fuel trims).
The O2 sensor on the right keeps saying it runs lean on petrol (0.03V), but okay on LPG (cycles normally). I took away the wires that go to the LPG computer because I suspected something there, but it made no difference. I swapped the sensors left/right and it stayed the same aswell. The sensor on the left bank does everything normal too.

The O2 sensor thing isn't really the problem I think, but more of a consequence. I managed to get my fuel trims reset (on accident I think, it happened when it ran with the right O2 sensor unplugged), but after a half hour drive, they were back almost the way they were.

These are the fuel trims right now:

On petrol:
Short term bank 1: -8 or -9 ish
Short term bank 2: +25
Long term bank 1: +8.59
Long term bank 2: -24,2
O2 sensor on bank 1 cycles normal, bank 2 says 0.03

On LPG;
Short term bank 1: -18
Short term bank 2: -19,5
Long term bank 1: +8.59
Long term bank 2: -24,2
Both O2 sensors cycle normal.
(now that I look at it, the left bank acts strange too. Maybe I should check that again because the way I remember, the left bank short term trim was positive.)


I'm getting TC's aswell, P0444 and P0154 alternately.
Wiring seems to be okay because I have a normal O2 reading on LPG, even with the wire to the LPG computer unplugged (ran bad, but I wanted to check).

I figured the problem might be that on LPG, the O2 sensors don't match the injecors, so I tried switching the signal wires for the O2 sensors left/right, but that didn't make it better. I tried changing the injector wires for the LPG injectors left/right, but it got worse again.

When the trims were reset, it ran great on both petrol and LPG, until the long term trims got bad again. I even went to the technical inspection because I thought it was ok, but the CO-value was too high; just above 1% (should be 0.3 or less). Lambda was ok though.


I'm lost. I like searching for this kind of problems and most of the times, I find them too. I'm sure it's something stupid or something small, but I just don't see it anymore at the moment. Maybe I should let it rest a couple days and start over with the thinking.

Anyways, if someone has an idea where I'm doing something wrong, I'd be happy to listen

Cheers!
Pieter

What LPG system do you have?

@kermit_rr Right up your street.

J

Can't believe I forgot to mention that; it's a Lovato multipoint injection which (I suppose) piggybacks off the petrol injection.

I'd say do a reset then run for a while on petrol only to get decent trims, i bet you'll find if you watch the live data the lpg is way off, could be the map or a leak, it even a blockage ie a filter, loads of reasons log will change the trims

Im not good in the proper language, but my old system piggybacked the petrol, which was great because it took a baseline from the petrol ecu, there was no real map as such.
My new one is in line and has a separate fuel map that you have full control over which is better in theory, but where i struggle.. if the map is slightly out then it affects the fuel trims and makes it run rubbish on petrol. This is where I'm at currently

Surely if the LPG is piggybacked on the normal fuel map in the ECM, then the trims on LPG will be all to cock, as the ECM can't alter the fueling of the LPG.

No it can't that's true, but the LPG computer alters the petrol injection signal so it works for LPG, right? Otherwise it would never be able to run on LPG

I'll take a look at the LPG injectorrail tomorrow. Didn't inspect that closely yet.
Maybe switch them from side

Oh damn I forgot something!!!
What value should I get with the O2 sensors debranched at the sensor side?
This morning I had 0.450V... Seems to me that should be zero, no? Or a TC at least but no, there was nothing

The old systems fake data so the petrol remains correct.
The new systems let the petrol ecu think it's running with actual data

PieterLV said:

Oh damn I forgot something!!!
What value should I get with the O2 sensors debranched at the sensor side?
This morning I had 0.450V... Seems to me that should be zero, no? Or a TC at least but no, there was nothing

Click to expand...

I thought optimum for O2(lambda) was 1. For petrol or any other fuel that was tying in and frigging numbers to run right. Need to refresh brain cells.

As said ^^^ run on petrol for a while to let it all settle then check data.

J

The problem is that I have to get through technical inspection before I can register it and drive it. I can run it up and down the street, but that's it.

Checked some things, changed some things.

I noticed that the tubes from the LPG-injectors were connected in an odd way. Cylinder 1 and 7 were connected to the rail on the right hand bank while 3 and 5 came -logically- from the rail on the left hand bank and vice versa. Changed it so all cylinders from the left hand bank are connected to the left hand injector rail and the right hand cylinders on the right.

Then I saw that the connectors were branched in a weird way too. A, B, C and D on the bank on the right and vice versa. Looked up the wiring diagrams for the Lovato Easy Fast systems and found that the loom which is connected to the petrol injectors and the loom for the LPG injectors, both have a red strap on one side. Of course, it was connected wrong (so petrol injector signal for bank on the right was copied for LPG injectors on the left hand bank). Changed it and drove around with high hopes... Sadly, short term trim keeps going negative on the right hand bank.
I tried switching the looms left/right again, but no good.

My last hope is a petrol injector who keeps firing. I'd try if it gets better by disconnecting the LPG injectors one by one, but then the LPS system goes in alarm and switches to petrol. I'd try by disconecting the injector tubes, but I have to find a way to get rid of the gas I think. Maybe outside when it's windy, don't want it to fly around when the engine is running and sparking an being hot.

Oh an I disconnected both signal wires of the O2 sensors and Ultragauge showed 0.450 for a while and then suddenly, the left bank went up to 0.8something and kept on changing. Is that the ECM who shows the values it guesses or is there something wrong here?


Cheers

The upper manifold on a Thor engine isn't how you'd expect, the manifold inlets aren't in order do it might have been correct to start with

Christ, of course, pretty stupid of me.

Can't seem to find which banana goes to which cylinder though Any idea where to go look?

I did find out.. it's on here somewhere!! I can have a look of mine tomorrow

I put them back the way they were, but left the loom the way it was, but it runs pretty bad this way. Guess I better check the order of the manifold real well.

Short fuel trim keeps going negative on the right bank, so I'm more and more suspecting some petrol that keeps getting in.

Damn, no-one who has a manifold lying around who can check the order? Must've come to the wrong forum

I tried disconnecting the signal wires to each of the petrol injectors one by one. Tried it when running on petrol and it ran slightly worse with each wire disconnected so there's no petrol injector stuck open.

Tried disconnecting them all when running on LPG and there was no change. Kept running with -25 short term trim on the right bank so the LPG computer cuts them off nicely.


Weird. I don't know anymore at the moment.