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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Discussion Starter #1
Hi all,

I have a bit of an issue with my 'rover... 2001 THOR engine... I know lots of people have had issues with throttling and idle controls and the likes, and I've searched this and other forums looking for answers and things to try. I'm the kind of person where I would like a few specific things to try and diagnose, then fix the actual problem, rather than throwing money at it, change lots of things, and then find that it was the simplest and cheapest thing last!

Engine cranks a couple of times and fires up - no real problem there. Generally takes a couple of turn overs before she fires - but doesn't seem abnormally long (especially as it isn't exactly tropical here)
Startup idle is a bit over the place for a couple of seconds, then she settles into a steady idle, below 1000rpm - once again fairly normal.

As mentioned, the RR runs a dual fuel system. The LPG is a very neat install, and from what I can gather is sequential multiport system, doesn't have a gas ring or anything like that.

The Problem:
When I put my foot down on the accelerator pedal very lightly, the idle becomes erratic, and gets very close to stalling - this seems to only happen occasionally though.
If you lift off the accelerator, to slow down (eg lights etc) and then put your foot back on the throttle, she seems to stumble for a second before pulling away. Once foot is down, acceleration seems to be smooth, as do gear-changes.

This is noticable on BOTH petrol and LPG - so think the problem must be a common component. She was serviced yesterday (Independant LR shop), and they did the standards fluids and filters, and the spark plugs have been changed.

Done So Far:

I pulled the Idle Air Control valve out last night to look at it, and it seemed to be OK. there was a little bit of residue in there, but it wasn't gunked or coked up - the valve itself was springy and could feel it moving as I handled the housing.

I took the TPS off and had a bit of a squizz. put a multi-meter over the pins and moved it.. it read between about 2ohms (throttle closed) down to about 0.9ohms. I wondered if this was the problem, but the resistance seemed to change smoothly as the TPS was adjusted, so think this is probably ok.

Looked at the MAF, and it looked fairly clean (the element on top was clean and shiny) I don't have any carb cleaner, so couldn't squirt the inside parts - will look at that next week.

The HT Leads do look a bit old, but I asked the garage to change them, and they said they would if they felt they needed doing, and since they haven't been done - I guess they felt they were ok.
The guy at the garage did say when I asked about it on the phone that could even be head gaskets :shock: especially as it's LPG - he said it starting on LPG could do it - but my system starts up on petrol and automatically switches over to LPG when sufficient temp is reached. also surely there would be other signs of that, especially in the engine oil when they changed it etc.

So... I open this up to thoughts and ideas... as I said, I have searched this and other forums, but a lot of the issues I've seen other people have are either on petrol only, or lpg only, not on both, or the problem has just been an erratic idle, but acceleration is fine.. reason I looked at the IACV and TPS was looking at the main site with regards to idle problems etc.

Thanks in advance for any input... Also just so you know, I'm away with work until Tuesday, from this evening - so will be able to get replies - but won't be able to look at anything on the truck until then.

Cheers,
Marty
 

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You don't give any details on the type of LPG system you are running.

This sounds like a possible MAF fault. Connect up a diagnostic reader and check MAF should get around 22-25Kg at idle and approx 90-100kg at 3000rpm. You could also disconnect the MAF and see if this makes any difference to running - this will probably cause the MIL to light. A basic check for the HT leadsis to park somewhere really dark and check if any arcing.
 

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Maybe something you've allready done, however any air leak can seriously bugger things up. Maybe check all the hoses that go to the inlet manifold.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Discussion Starter #4
Hi Guys,

Thanks for the replies.

AMcK, to be honest I don't actually know what model of LPG system it is. I need to hunt that out somewhere as there are no apparent stickers or manufacturer names anywhere under the bonnet. I'm fairly sure it's been done properly as it's actually been registered with DVLA as dual fuel. I'll see if I can find out and will post back.

MAF is on the list to be cleaned when I get home on Tuesday. I need to get an OBD II scanner at some point. Faultmate is on the list of to get, but funds aren't quite therev t the moment - more important things on the list :)

Will also look under the hood in the evening to see if I can see any arcing.

Benji, will do a thorough check of air intake system also and will see what I can find. Is it worth trying to take throttle body off and cleaning it too? though if IACV is clean, then I would think it's probably clean enough?

Thanks for the ideas. Will let know how I get on.

Cheers

Marty
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Discussion Starter #5
Hi All,

A bit of an update for anyone who may have an idea...

I've not really had a chance to do a lot to the 'Rover this week - mainly due to other commitments, and I'm off away again tomorrow for work - for at least another week... grrr (at least it's paying some money... probably to help look after the RR!!)

What I have done:

Cleaned the MAF - got some Carb cleaner and sprayed it all through really good... cleaner came out clean the other side, no sign of any dirt/crud or otherwise in there.
Looked under the hood in the dark with engine running - no arcing could be seen anywhere from HT leads.

I did notice a slight 'ticking' noise, which I don't remember hearing from my previous P38's - but they were both GEMS units, not THOR - so I don't know if there are any other quirks or noises from the THOR ones - due to the extra smog bits, or from the LPG install - I haven't had time to probe into where the ticking sound is coming from either... sounds like top of the engine somewhere.

Idle seemed to be ok today, but if you put foot down on throttle sharply, then she definitely stumbled before catching up.

So, no more real food for thought - Same symptoms as before, and no real idea on the cause. I don't currently have access to an OBD II scanner to read any fault codes, but then other posts I've seen with these sort of issues don't seem to throw up any codes, it's just a pain in the arse to diagnose!!

If there's anyone around Wiltshire, or in neighbouring counties that has some experience in engine troubles, diagnosis and the likes, then I'd be welcome of someone else having a look over it. I'm more into the electrical side of things, and have re-built EAS on my previous Rovers, but I feel engines are a little bit out of my league!! I'd love to be able to fix it myself, but something tells me that without being able to have access to all the tools, diagnostics, and the likes, I'm just going to be poking around, hoping to get it right!!

Cheers for any other ideas/suggestions!! I'm back home in a week or so, and will try out anything else that's mentioned, or chase up any other leads!

Martin
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Discussion Starter #6
**update**

Right,

I have had a bit more of a look into this - and know someone who's a mechanic, who has been to have a bit of a check over the RR, from an engine/mechanical point of view.

He seems to think that it's in pretty good shape, doesn't sound to him like there's compression problems, and sounds fairly normal whilst idling/running.

The throttle response problem is still there, though - he's going to see about checking the emissions (also to help rule out head/block/gasket issues).

Seems to be worse once the engine has warmed up though. If you sharply step on the throttle (as if to accelerate to overtake for example), then she shudders/bangs once before taking off. So I guess it's something to do with the fuel/air mix. I am leaning to it being too much air, not enough fuel - as on my previous RR's if you had any signs you got more of a pinking noise, which sounded wet, like too much fuel/not enough air.

So... what's the best place to start with bits to swap out? It does it on both petrol and LPG, so I'm going with it's something that's common to both.

Don't think it's IACV, as it does seem to idle ok. Starts on petrol, and automatically switches to LPG when warm enough. no shudders or stumbling in the switch to/from LPG

As mentioned before, have tried cleaning the MAF, no crud came out at all. I don't have access to Diagnostics to check the flow through it, and unsure about just unplugging it. will the MIL light come on, and if so, will it need a reset once MAF is plugged back in?

TPS.. seems to be ok - I measured resistance across it, and IIRC it was about 2.01 ohms when closed, through to about 0.98ohms when opened (maybe it was k ohms - was a couple of weeks ago when I checked). but I can't find any information pertaining to what the values should be, so know way of knowing if they're in a proper range. Though the other thing is, if you're gentle on the throttle, then there's no problem - which to me is a case of it's sensing throttle OK, just just taking a second to react to the change.

CKS: Crank position sensor.. haven't looked at it yet - been too cold and snowy to crawl underneath at the moment!
CPS: Cam position sendsor.. once again, haven't looked at it yet - but I would have thought that if either this or CKS were faulty, then there would be symptoms under normal driving conditions too?
HT Leads: once again, looked for any arcing in the dark, and none apparant. they do look a *bit* old, but I told them to change at service if they needed doing.. and they did the plugs, but not leads...

I'm tempted to upgrade to some Magnecors at some point anyway, and whilst the plenum chamber is off, fix a rocker cover gasket... but will look at that at some point when my mechanic mate has some time to help me!!

any other thoughts/opinions?

Oh, and LPG system... I still don't know for CERTAIN what make/model it is - as the ECU is bolted in and no visible stickers... no visible markings on the vapouriser either... though the tank in the back has BRC on the centre of it.. so I don't know if that means the whole system is likely to be BRC, or whether it's just the tank that is!

Thanks in advance for any replies :)
Marty
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Discussion Starter #7
**update**

Hi all,

Sorry for the long delays in posting an update here... had other things to contend with... work, replacing the heater matrix (now have an Audi one and NO O-rings!) recarpeting the interior due to the mouldy carpet from leaking sunroof drains, heater core, and missing pollen filter....

But as far as engine is concerned:

Spent an afternoon removing inlet manifold, and replacing rocker cover gaskets (was told one was leaking, so figured I'd do it whilst I was doing HT's), I've cleaned the throttle body, bypasses throttle plate heater, replaced HT leads, put a new TPS and MAF in, and had a general look see at the rocker breathers etc.

It's all back together now... I've also removed the CKS and cleaned it, and the surrounding area. I've tried to look at the reluctor ring, but had little luck seeing any of the teeth through the CKS hole... the inspection hatch on the bellhousing lets me see the back of the flywheel (just) and front of torque converter, but once again.. not reluctor ring. I've read on here that the inspection hatch is half moon shaped, but mine is just a circle, bolted on with 3 bolts... has this changed for the THOR models? or is there another hatch I've missed?

I did poke my finger up through the round hatch, and couldn't feel any reluctor ring teeth, bits of flexplate etc - and the CKS shaft was nice and straight.

Anyhow... after doing the first bit, she started up ok, but the problem was still there - put your foot down sharply and it would feel like it would stall, before catching up. Since pulling the CKS and cleaning it (I paid careful attention to reassembly, making sure the spacers were in the right place etc) when she starts, she idles about 2000rpm and then slowly (after a few minutes) it creeps down to about 1000rpm... it will then start 'seeking' a bit, the rpms will drop a tiny bit, then come back up... wait a bit, do it again... I don't know if this is the ECU slowly 'learning' the new values of the sensors, or whether this is still an underlying issue...

I've taken it to a local service place today, which I found on one of the other LR forums when searching google for LR places around Swindon, and there was a recommendation that there was a guy there (Simon) at SVS - Sheer Value Services (now Red Dot Cars) - who knew his stuff on P38's, and had diagnostics etc... however, now it's there - I don't think Simon is there anymore either - I've had a call from them saying that it depends on how much I want to spend on it, could cost £400-500 or up to £1000 to fix... but their LR diagnostics are away being fixed at the moment (was told this on the phone AFTER I'd got back home!) so they can't pull codes etc.

I had originally booked it in there, as they said they had LR Diags and I wanted firstly for the adaptive values reset, now that the MAF and TPS are new... but they can't even do that it seems... I got a bit short with the guy who called me, because I don't like being told that it could cost lots to fix, when they can't even do the specific things I asked them to... The guy said he'd go back and have another talk to the mechanic (Dave), and they'd call me back... that was 2 1/2 hours ago now, so think I might be chasing them up soon!

Any other thoughts/ideas? I'm going to look at getting an ELM327 bluetooth OBD scanner soon, as that will at least let me see live data, and any fault codes... will be an interim until the pennies are there for a Nanocom Evolution... maybe I could then go back to the service place, and show them how to do it!

I am tempted to get a replacement CKS, since the 2000rpm idle thing has been since I've removed it and cleaned it??

Also think a new water pump is on the short list... found traces of a few coolant drips at the front of the engine :(

Thoughts, Ideas, etc all welcome!

Oh, I've also tried PM'ing allyv8 as I know he's had a look at other people's P38's with these kind of issues, and been able to sort it out... he's also about 30miles from me, but I haven't had a reply yet - so I don't know if he's still kicking about in the forums!

Cheers all,
Marty
 

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Re: **update**

your [thor] reluctor ring is different to GEMs, its a much better design and can't whack the CKS any longer. half moon inspection plate is also a GEMs only feature, its basically [what is now] the vertical face of the oil sump on the Thor.
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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4,159 Posts
Discussion Starter #9
Re: **update**

@LarryS

Thanks for that!!! I had wondered about that, but hadn't got the time to delve into RAVE and look at the specifics of it. Much appreciated for clearing that up!

Marty
 

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Re: **update**

no problem, for what it's worth i have the OBD bluetooth 327 and although the wireless is great it does drop out after a bit, this of course maybe just me and my XP laptop also it maybe responsible for "interfering" with the ABS ecu as i realized sometime after using it that the ABS/TC/Brake lights all took longer to go out, again could just be me, their very cheap @£12 but i would get the wired version if doing it again - its not a lot either way.
 
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Re: **update**

After changing the CKP (anyway, you may as well..) I would next check all the various temp. sensors (and try the 'propane' check on the inlet for vac leaks).

Has the car always been like this ? LPG conversions involve various drillings (here and there) and tend to be 'custom' jobs......... and some 'spoof' the O2 sensors when on LPG.

{Larry S. : Don't like the bluetooth OBDII much myself. In theory the ABS ECU etc are protected from such RF Ingress / Interference but nothing surprises me any more about LR electronics..}
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Discussion Starter #12
Re: **update**

Hmm, there are a couple of vac hoses from the inlet manifold, but I'm pretty sure they're ok - I had a look over whilst the manifold was off - but another squizz can't hurt!

I've only owned it since January (and it's spent most of that time sitting on the driveway in various states of being pulled apart!) and I get the distinct impression that the previous owner drove it, and didn't do anything else to it. It had an MOT, needed 2 new tyres, which were done, but that's about it. I knew there were a few issues with somethings (in one of my other posts) and I've so far all fixed them! (touch wood!)

When I was out on the test drive (he drove it, because of insurance etc) I didn't notice any signs of stumbling, idle problems etc. However, it first did it when I went and brought it home - once when I was sitting at the lights. - and since then it has done it more often - and as mentioned, on both fuels.

the LPG system *looks* like it's been professionally done. From previous tax discs I've found, it looks like it has been LPG since at least 2008...

The LPG system is a Zavoli Alisei sequential system. Injectors are at the back of engine by firewall, and hoses run to inlets next to the fuel injectors. Once again, all looked secure when the manifold was off, and looms etc have been run for it - the ECU is in the compartment behind the battery where the GEMS ECU would usually sit.

I'm not sure what it does regarding the O2 sensors... I did look it all up, but can't remember what it said!

One point to not though, since doing the work on the engine, having sensors replaced etc - I have ONLY run it on petrol... I have used the selector switch to make sure it doesn't switch to LPG once warm. I figure it's best to get it running right again on petrol, before trying to confuse the poor thing with LPG too!

Cheers,
Marty
 
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Hmmmm... interesting, did the vendor demo it with LPG only ? I tend to view these conversions as optimised for LPG use, as it is cheaper, and so there may well be issues with petrol ?? I have seen a couple of conversions (although not P38s) where the throttle butterfly was drilled, too... with a view to the different idle requirements for LPG.

After all your changed parts it may be a good idea to see how it runs on LPG now (ie. for a while rather than a 'quick change-over')

- Are there any discernible differences at all between performance running on either fuel (eg from/when hot/cold/etc) ?

Not quite sure but running diagnostics twice, ie. with both fuels in turn, may also yield some useful info, too (as long as they don't charge you twice, obviously !)..... although unfortunately when running on LPG you may get some strange (ie. unusual) sensor readings etc on the diagnostics equipment, too.
 

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Re: **update**

i would look closely at the O2 wiring and how their split between the two systems, the CKS if it's old is certainly a candidate - have you done a compression test ? (Sorry if you have, rather long posts to go through)
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Discussion Starter #15
Re: **update**

Ok,

So just been on the phone to the service place.... They say they're not really willing to get to far into it, as it also seems to be smoking a fair bit...

I asked them what kind of smoke - where's it coming from etc, is it burning oil etc.. and he queried their 'expert' and he said that it was in the cabin... To which my response was (I had told them when I dropped it off too) that it's just had a new heater core and I think it's probably burning off the residue from manufacturing process (I forgot to wash the core before installing it... DOH) he went away and mentioned that to the mechanic and came back with "yeah, it could be that actually"...

They've also recommended I take it to a gas specialist to get it looked at, as they think it could be because the gas system retards the timing or something... Which I can understand their thinking - but as mentioned before I'm not running it on gas at the moment.

Vendor had it running on LPG, but I got him to switch between the 2 fuels whilst on the test drive... also, even if you start the vehicle from hot, it will still start on petrol before switching back to LPG.

I'm also pretty certain it was running on LPG when it first did it on the way home from picking it up too...

Throttle butterfly is not drilled - and is completely intact. It's also been cleaned when the manifold was off.

Discernible differences between fuels... before I did the sensors etc - the problem seemed a little bit more apparant once it had warmed up - but also there was no real rhyme or reason for it... it only really happened on sharp acceleration, though randomly would do it on idle too. Once the throttle was pressed and you were accelerating then was smooth, no signs of misfires etc. as for between fuels, no real difference - problem was present on both fuels, and the same sort of severity too.

@ LarryS I will have a look at the wiring of the O2's and see if there's any sign of splices etc. No, I haven't had a compression test done - but have a mate who's a mechanic who can do one for me at some point. He's had an emissions test done, (he was worried originally about hydrocarbons etc/burning coolant etc - and apparantly it was a tiny bit high/running a bit rich - but not off the scale like he'd expect for HG problems.

Right... off to pick her up... will be back soon... they don't have their diags back, so think I will look at investing in my own!

Cheers as usual!

Marty
 
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Obviously your garage operates a 'no-smoking environment' in tandem with their 'take it somewhere else department' !?

To be fair it may indeed help if you get some more details on your LPG system and particularly the piggyback ECU it uses, and just how this interfaces with your LR one ( and what, exactly, it spoofs, and when/how).

-It may also be possible to get some diagnostic info. from the LPG ECU by interrogating it directly; There is special PC S/W available for this via the LPG forums etc: www.zavoli.com/upload/manuali/en_file_6.pdf

The key question here is does any of the LPG ECU (still) affect the Thor ECU when switched to petrol...? Otherwise some LR diagnostics results may be rather misleading unless the two ECUs can be completely separated ?

Anyone reading this actually carried out standard diagnostics on a Thor/LPG conversion ??
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Discussion Starter #17
Hi Dave,

I have the girl back now :) she seemed to run a bit smoother on the trip back - I also let it cut over to LPG when it saw fit, and ran fine like that too. I purposefully didn't stamp my foot down to see the reaction! when I started it up to leave the garage, it idled about 1500rpm, not 2000 - and by the time I got home, and parked up the idle was under 1000rpm. It almost had a little hiccup when I selected between drive and reverse quickly (load off engine, then back on quickly) to manoeuvre in the drive. I will look into the LPG side of things a bit more when I get the time... got the girlfriend coming out this afternoon, so will have to give the other (primary of course) lady in my life a bit of time!

I've taken some pics of the split charge system, so will post them in the other thread... did notice however when I opened the bonnet that it was stinking hot under there... got the IR thermometer and took some readings... top end of engine/radiator hose was about 75 degrees C, expansion tank was about the same... bottom of the radiator/thermostat was about 34 degrees C... this doesn't sound right after the car's been stopped for a couple of minutes?!? buggered thermostat? clogged radiator (there didn't seem like there was a lot of gunk in the radiator when I drained coolant before)?? something else for the shopping list??

I get a bit of a feeling that the ECU is re-teaching itself, since it does seem to be a bit smoother and the idle speed does seem to be coming down a bit... but who knows!
 
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(Don't quote me but) I had a quick look at a 'typical' installation of your LPG system and it is not particularly complicated, it basically takes the ECU pulses intended for the petrol injectors and interupts/converts these to pulses for the LPG injectors, thus it does not spoof the O2 sensors like some systems. Based on this for a start I would check the LPG ECU connector(s) (for good contact) and also the loom to/from (all) the injectors for good continuity, too, as these are responsible for the flow of fuel of either type !

Good to hear she is running a little better (the car of course) but the garage may have been running the engine for some time whilst stationary ...which gets things hot faster... but you are right to monitor it (carefully) anyway !!
 

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LEGACY VENDOR
1995-2002 Range Rover P38A
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Discussion Starter #19
Hmm, thanks for looking into that for me Dave :) If the LPG system takes/interrupts the fuel injector pulses, and doesn't do anything to the O2 sensors, then I guess that's a good thing right? Means that any adjustments the Thor ECU makes to injector timing etc will be mimicked by the LPG ECU and thus as far as the vehicle is concerned, it's made the change?

I will have a look at all the ECU cables once she's cooled down a bit.

When I picked her up, the temp gauge was just above cold - and the drive home was about 5 miles... not sure what that's like on temperature for that kind of run - probably split 50/50 between 30mph and 50mph zones...

I'll do a search now, and see what the traits of a faulty thermostat are :)

Marty
 
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No problem Marty, in fact I researched all this a while back whilst considering an LPG conversion myself, but I was quickly 'cured' of this when I happened on a garage who were replacing a whole top end on a P38 that had been the subject of a very basic LPG installation... ie. 'a bad conversion gone worse'.. [& you can buy a lot of petrol for £5K, even at our inflated UK prices.]

I probably simplified it a bit too much but all your assumptions in your first paragraph are basically correct.

'Stinking hot' on a 5-mile 30/50 mph run from cold @15C ambient ??
No, Not good.... you may want to check the viscous fan, too !
 
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