LPG Vs MAF no winners... I Need Someone With Experience

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Doo

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As per title, the MAF flags up a fault that it is dead! The symptoms I get are slight hesitation upon very light throttle, but most noticeable when pulling away from stop.

Hamish convinced it is an LPG created problem and could be wiring to MAF from the LPG nonsense.

I want it gone, both fault and LPG so am happy to rip it out. But need someone with LPG experience to tell me how I can find the wiring joints and repair them to factory standard.

I can state the fault doesn't get worse and the car passed the emissions test, but it is running slightly rich and the exhaust tips are sooty. MPG has dropped to 16mpg on a long run as opposed to a decent 20/21mpg previously.

I will be happy to provide any more info should it be requested.

So far, I removed the gas pipe from the tank and the cooling pipes to the gas distributor thingy (big & round & under the bonnet taking up room o_O )

Thanks lads

Doo
 
position of the lpg ecu will depend on supplier who fitted it, mine for example is fitted in to the top of the ebox (big black box on drivers side) you will also find the inlet manifold will have been drilled & tapped to fit in gas injectors so you will need to replace that as well.
 
RRkev said:
position of the lpg ecu will depend on supplier who fitted it, mine for example is fitted in to the top of the ebox (big black box on drivers side) you will also find the inlet manifold will have been drilled & tapped to fit in gas injectors so you will need to replace that as well.
Click to expand...

I could just as easily leave the gas injectors in place to keep the manifold vacuum sealed, but I realise that it needs replaced at some point.

I really just need some advice that points me in the direction of safely removing all the LPG nonsense as far as the wiring goes. I understand the ecu and all that are still in place and can be activated as per the button on the dash.

So, if I find the make, I can state model & serial numbers and someone will say, the green wire attaches to the black wire with red trace going to cars own ECU, pin 23 or some such? All I want to do is remove the LPG wiring, solder & heat shrink the original wires back into their place.

Cheers :)
 
unfortunately it's not going to be that easy, there is no set way or locations for installing the lpg components, it really is down to the fitter where he installs the relevant parts. so it's a bit of a minefield. why not just leave the lpg system on and just run it on petrol? if there is no gas in the tank it will use petrol anyway.

as for the manifold, it may not keep a vacuum by leaving the injectors on, they may open once power is removed or may already be leaking (i've just had major running problems caused by leaking lpg injectors.
 
LPG shouldn't have any interplay with the MAF. The MAF reads air before the inlet manifold.

the only issue I have had with LPG on the P38 is plug replacement, spark plugs will last a year or a little bit more. the symptoms you have posted are like worn plugs. a set of 8 BPR6ES sets me back about £16.00.. pull the plugs an have a look first off

if the MAF is on the way out LPG or not, it'll need a new MAF. don't waste your time or money with pattern ones, only go for Bosch
 
There's one tap into the engine ECU. That's it. The injector loom couples under the petrol gallery. Don't condemn LPG. P38'S love it. I wouldn't win votes for some installers . The injectors are no more than nozzles when work loose mix everything a bottle. Diagnostics don't care what fuel is in use. If your maf doesn't come up to muster LPG isn't the problem. In the old days of dumping gas into the manifold the maf sensor would take a hit on every spit back. Second the plug choice. Shut the gap up to hell. 27 thou is the spec. Don't be bashful. 25 or a bit less changes the world.
 
We found that our Discovery V8's ran well with 30 thou gaps on the double platinum plugs, but the combustion heat tended to open the gap by distorting the ground electrode.

I think we run Champion plugs, ours are OEM numbered 7318, we get 60K+ miles out of them.

Peter
 
Likewise,

Don't see why you'd want to get rid of the LPG - but it's your decision I guess.. I've covered probably 2K on LPG now since putting the new engine in and it's running sweetly.

MAF fault is probably just that, a fault with the MAF.. modern sequential LPG systems with injectors for every cylinder don't backfire through to the air box and destroy the MAF like the old single point systems do - and as has already been stated, the MAF has no connection to the LPG system at all.

The LPG connections to the petrol loom will be:
Switched positive connection - wiring diagrams usually show this as coming from the +ve supply to the injectors
16x injector connections - a feed from the petrol loom, and a return back to it, so the LPG ECU then can switch between connecting the petrol injectors and emulating them back to the petrol ECU when running on LPG
Some systems have a connection to the lambda sensors - though again they aren't used by the LPG system - but are sometimes plumbed in so you can read from them when calibrating the LPG system.

The sequential LPG systems just slave off the petrol injector timings - so the petrol ECU is still the one running the engine, the LPG ECU just cuts off the petrol injectors, reads in injection pulse time, adds it's 'fiddle factor' for the LPG injectors, and fires them at the correct time.

If you have a MAF issue, then when you pull all the LPG stuff out, you'll still have a MAF issue.

Again, as also mentioned - if a Motronic vehicle - only get a genuine Bosch MAF - the aftermarket ones work, but they aren't obviously to the same tolerances as the genuine ones - so they will eventually cause problems, generally by pulling the fuel trims out of whack and causing rich or lean running as they are over/under reporting the air flow.
 
Thanks for the input guys.

1st replacement was a brand spanking Bosch MAF, followed closely by another Bosch MAF :eek:

Next, spanking new plugs at 60 quid for the lot (the old ones had been perfect and barely covered 8k, I still have them).

I checked in the dark for misfiring leads (they were brand spanking new grey ones 8k ago) and not a peep. I tried those red plug things that show all plugs are sparking and guess what? All plugs were sparking.

I did find a slight vacuum leak & replaced the hose as it had been tee'd with a feed to the LPG distributor wossname, that helped, but didn't cure the slight miss.

Each time, the expensive reader (it's the real deal 14 inch touchscreen for Land Rovers) shows it has a MAF fault. It clears it, shows no faults, I drive it and it returns. Surely two new Bosch MAF's couldn't be bad?

Hamish convinced it's an LPG wiring fault, but I wonder if it may be the plug going onto the MAF or the wiring from there to..."where?" ECU??
 
Just to throw a spanner in the works, my cruise stopped working too... All new pipes, wiring perfect, just no cruise!

Height adjustment out of kilter, needs blocks to reinstate each height and programme it, but would "that" throw CC out??
 
Doo said:
Thanks for the input guys.

1st replacement was a brand spanking Bosch MAF, followed closely by another Bosch MAF :eek:

Next, spanking new plugs at 60 quid for the lot (the old ones had been perfect and barely covered 8k, I still have them).

I checked in the dark for misfiring leads (they were brand spanking new grey ones 8k ago) and not a peep. I tried those red plug things that show all plugs are sparking and guess what? All plugs were sparking.

I did find a slight vacuum leak & replaced the hose as it had been tee'd with a feed to the LPG distributor wossname, that helped, but didn't cure the slight miss.

Each time, the expensive reader (it's the real deal 14 inch touchscreen for Land Rovers) shows it has a MAF fault. It clears it, shows no faults, I drive it and it returns. Surely two new Bosch MAF's couldn't be bad?

Hamish convinced it's an LPG wiring fault, but I wonder if it may be the plug going onto the MAF or the wiring from there to..."where?" ECU??
Click to expand...

ok. here's a question... do you get the symptom on LPG or Petrol or both ?

I'm not convinced its the LPG wiring..

I did the same as you and bought the top end premium plugs for LPG. they lasted barely a year and it hesitated and stuttered all over the place when the plugs went bad. BPR6ES last longer with LPG / Petrol and as I say I pay well under £20 for a set of 8.

if its the expensive reader... what does the live data show.. you'll see on there straight away what the MAF is reading. also is it misfiring.. if so on what Cylinders. the coil packs are redundant spark so if you have a coil pack go bad, you'll get the misfire on the opposing coil pack circuit IE 4&7 / 1&6 / 5&8 / 2&3

I'd be highly suspicious of 1 Bosch Maf going bad. let alone 2... changed the air filter lately ?
 
martyuk said:
Likewise,

Don't see why you'd want to get rid of the LPG - but it's your decision I guess.. I've covered probably 2K on LPG now since putting the new engine in and it's running sweetly.

MAF fault is probably just that, a fault with the MAF.. modern sequential LPG systems with injectors for every cylinder don't backfire through to the air box and destroy the MAF like the old single point systems do - and as has already been stated, the MAF has no connection to the LPG system at all.

The LPG connections to the petrol loom will be:
Switched positive connection - wiring diagrams usually show this as coming from the +ve supply to the injectors
16x injector connections - a feed from the petrol loom, and a return back to it, so the LPG ECU then can switch between connecting the petrol injectors and emulating them back to the petrol ECU when running on LPG
Some systems have a connection to the lambda sensors - though again they aren't used by the LPG system - but are sometimes plumbed in so you can read from them when calibrating the LPG system.

The sequential LPG systems just slave off the petrol injector timings - so the petrol ECU is still the one running the engine, the LPG ECU just cuts off the petrol injectors, reads in injection pulse time, adds it's 'fiddle factor' for the LPG injectors, and fires them at the correct time.

If you have a MAF issue, then when you pull all the LPG stuff out, you'll still have a MAF issue.

Again, as also mentioned - if a Motronic vehicle - only get a genuine Bosch MAF - the aftermarket ones work, but they aren't obviously to the same tolerances as the genuine ones - so they will eventually cause problems, generally by pulling the fuel trims out of whack and causing rich or lean running as they are over/under reporting the air flow.
Click to expand...
that's what I meant. There's two solonoid valves that need to kick in. There's a single tapping that picks up the engine ECU happenings. The LPG ECU only does what the engine ECU does. If you could see what's going on in a software programn the LPG emulates petrol. It would be a more practical option to restore the LPG install than to ditch it. Most troubles mirror troubles full stop. I might not be a wizard on landyzone but you want someone with experience. Speaking.
 
I DO NOT use the LPG. End of.

I did ask for live data, but not happening as they so busy :(

Plugs identical to ones bought last year, and they initially were perfect for at least 7k

It's only on light throttle setting when pulling away, but push it down harder and she's off, mint.

Air filter is also mint.

No one seems to understand why the MAF suddenly "dies" and misfires. But it doesn't die, it is fine after a reset and will do a few miles before the "small" misfire returns, but like I said, "only" when pulling away from a stand still.

I could reset it, drive a few miles and it will start misfiring, reset it, it will drive a few miles, then ...... You get the drift :eek:
 
Doo said:
I DO NOT use the LPG. End of.

I did ask for live data, but not happening as they so busy :(

Plugs identical to ones bought last year, and they initially were perfect for at least 7k

It's only on light throttle setting when pulling away, but push it down harder and she's off, mint.

Air filter is also mint.

No one seems to understand why the MAF suddenly "dies" and misfires. But it doesn't die, it is fine after a reset and will do a few miles before the "small" misfire returns, but like I said, "only" when pulling away from a stand still.

I could reset it, drive a few miles and it will start misfiring, reset it, it will drive a few miles, then ...... You get the drift :eek:
Click to expand...

Aaaaaannnnnnnnd it "always" flags up that the fault is MAF.

Had it been a turbo diesel, I would think turbo intercooler or hose burst/leaking. But this is showing the MAF wiring "at" the MAF.
 
I had precisely that problem. Admittedly I'd had a pretty major meltdown involving an ECU switch but in the end I changed the maf sensor after the lambda's. The symptoms you describe I partly ditched by kill or cure cotton bud and meths on the maf element. (Meths is all I had). It improved things which gave me a clue. I'd previously switched a suspect maf sensor for a supposed genuine Bosch. Yeah right. Got the wrong end of the stick, sorry, bout the LPG thing. Trying to help. Nite.
 
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supapete said:
I had precisely that problem. Admittedly I'd had a pretty major meltdown involving an ECU switch but in the end I changed the maf sensor after the lambda's. The symptoms you describe I partly ditched by kill or cure cotton bud and meths on the maf element. (Meths is all I had). It improved things which gave me a clue. I'd previously switched a suspect maf sensor for a supposed genuine Bosch. Yeah right. Got the wrong end of the stick, sorry, bout the LPG thing. Trying to help. Nite.
Click to expand...

Thanks Pete, and don't worry, none taken ;) I (and the guys at the shop) am/are simply trying to work out how, when the MAF code is cleared it works for a few miles then goes haywire again o_O:eek::rolleyes::confused: Is it possible that the voltage it gets to heat the element suddenly isn't "quite" enough so it decides to go faulty??
 
I don't know why clearing the code makes it better for awhile - maybe it runs in open loop, and then when it goes back to closed loop it starts playing up.
On mine when it went faulty, it would pull the fuel trims to the extremes, causing misfires and general bad running at idle - get above that, and it was happy.
I could reset the adaptive values on it, and it would run fine for awhile, but slowly pull the trims out again, and then the process repeated. The new Bosch MAF sorted it totally.

The older GEMS MAF's seem to respond to being cleaned, the Bosch ones don't seem to make a difference if you try cleaning them or not - once they've gone faulty, that's it.

LPG - I'm out too then. Good luck, you'll need to find however it's been installed and then cut out the LPG loom and reconnect the petrol injector wiring back together. Shouldn't be hard to do as RAVE/ETM will have all the P38 wiring colours in them, so just join like for like again.
 
martyuk said:
I don't know why clearing the code makes it better for awhile - maybe it runs in open loop, and then when it goes back to closed loop it starts playing up.
On mine when it went faulty, it would pull the fuel trims to the extremes, causing misfires and general bad running at idle - get above that, and it was happy.
I could reset the adaptive values on it, and it would run fine for awhile, but slowly pull the trims out again, and then the process repeated. The new Bosch MAF sorted it totally.

The older GEMS MAF's seem to respond to being cleaned, the Bosch ones don't seem to make a difference if you try cleaning them or not - once they've gone faulty, that's it.

LPG - I'm out too then. Good luck, you'll need to find however it's been installed and then cut out the LPG loom and reconnect the petrol injector wiring back together. Shouldn't be hard to do as RAVE/ETM will have all the P38 wiring colours in them, so just join like for like again.
Click to expand...

You see what I'm up against!

Thing is, she always starts beautifully hot or cold, idle is perfect (except when he re-set it, took an extra revolution to start the engine then idle was up & down, lumpy then rough but ruining). It's only on a smidge of throttle I get the "lack of petrol" sort of misfire. But put throttle pedal down a little or a lot and she's off like a racehorse. Drives pretty well, if a little rich feeling, all day. Then, if you stop, pulling of is tiny bit of splutter again, but so small, you can live with it.

But, the biggest BUT is why the Feck is, it coming up with the dead MAF code??

Driving me mad!!
 
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