ecu- new for old straight swap?

I'm currently- no pun intended- checking the continuity on a feed from ecu to th coil pack on a 4.0 2001 thor engine. seems I have a misfire on cylinders 4+7 caused by a weak spark. Ive already changed the HT leads, both coil packs and the MAF sensor to no cure of the problem. The only place I see to go now is further back down the ignition circuits from the coils to the ECU. Hence the continuity test on the feed wires to the coils.

I've just had the car converted to run LPG also. The misfire has been more prevalent since this and have read an interesting thread on here from a 2000 disco about the ecu being thrown out fuelling wise but would this affect spark?

Basically my question to the LandyZone is if the feed wires to the coils are all good I'm most probably looking at getting a new ecu. Would it be a straight swap, new one for old one (NNN 100 660) or are there various codings involved with diagnostic equipment needed??

Are you still using the silly platinum wide gap plugs ? Standard NGK BPR6ES plus at 25thou gap are much better. What method leads you to conclude a weak spark ?
An ecu swop - with a s/hand unit will need a security relearn to the BECM via Testbook or similar

We've used a Champion Double Platinum plug set for over 64k miles with no problems at all, not sure why you think they are 'silly' ? We run LPG as well.

The recommended plug RC11PYPB4 is also a Double Platinum plug, so I can't see why Rover's own recommendations should be ignored, or called 'silly'.

Peter

Ok,maybe not silly,unnecessary then. Just remember its still a 1954 Buick 215 engine - nothing more.Using electronic ignition and the very wide gapped platinum lugs results in VERY high peak HT voltages,which is very hard on plug leads,esp in damp conditions.Many people bang on about various makes of leads/plug etc,but in truth all that is needed to fire petrol or LPG in an old Rover is a 25thou gapped standard plug.This keeps the peak voltages down to 12-14Kv,which a half decent lead should be able to cope with.The trouble is a low performance v8 like a Rover is so smooth even with partial or repeat misfires the driver will not notice it.Read the misfire log in the Thor ecu and you will soon see a pattern.These misfires,even though you cant feel them cause havoc with the long term fuel trims,often made worse with badly trimmed LPG ecus - which probably at least 80% of them are.
The other thing about the platinum plugs in Rovers is that they last too long,72k is a bloody long time to leave a plug in an alloy head,many drag the threads out on first removal. Out with the thread inserts,more time,cost,etc,etc.
So make up your own mind,luckily I dont see many of them any more,but it was a pointless change to something that already worked well and the change gave no performance/economy or emission benefit at all - just more potential hassle.

We pulled our plugs every 12k or so and used Copaslip on the threads each time, never had a problem.

Old design it may be, but with Bosch Motronic control and a reasobable compression ratio, it's not that outdated.

Our plugs were swapped for new art 62k miles, still running OK.

We gapped ours to 35 thou, but we find that the outer contact bends away with heat, so need closing up every time we pull them.

We use STI leads, but the older Champion leads seemed OK, don't know how old they were, a new set from ebay were rubbish, broke down in minutes....

Don't forget (I'm sure you know this) that you are relying on TWP plugs to fire, not one, Lost Spark is hard on leads for that very reason, and induced current in the leads where they lay together.

Peter


Peter

listerdiesel said:

We pulled our plugs every 12k or so and used Copaslip on the threads each time, never had a problem.

Old design it may be, but with Bosch Motronic control and a reasobable compression ratio, it's not that outdated.

Our plugs were swapped for new art 62k miles, still running OK.

We gapped ours to 35 thou, but we find that the outer contact bends away with heat, so need closing up every time we pull them.

We use STI leads, but the older Champion leads seemed OK, don't know how old they were, a new set from ebay were rubbish, broke down in minutes....

Don't forget (I'm sure you know this) that you are relying on TWP plugs to fire, not one, Lost Spark is hard on leads for that very reason, and induced current in the leads where they lay together.

Peter


Peter

Click to expand...

The trouble is LR didn't see fit to put any thread lubricant on the plug threads at the factory,and were happy to state 72k service intervals - by which time most were well out of warranty and into second or third ownership.It was clearly some clever pratt trying to modify a 1950's pushrod motor.Whilst the Thor manifolding is a modern addition along with closed loop injection and distributorless ignition,which makes for smooth running and good emissions - there is nothing at all different in the combustion chamber or valve actuation.The combustion events in those engines simply don't need a huge spark,the engine even runs a lower CR than the old P5 engines which ran reasonably well on carbs and dizzy.
I would hope to understand wasted spark ignition by now... I was the third independent in the west country to buy Testbook back in 2003 when it became available and with the help of that and Pico oscilloscopes I've been sorting out running and emissions faults ever since.Including tuning and repairing countless badly set up LPG systems - which is why I generally have a poor opinion of them.

eightinavee said:

Including tuning and repairing countless badly set up LPG systems - which is why I generally have a poor opinion of them.

Click to expand...

Presumably you have seen a few that were done properly?

We've been very pleased with ours, but we have the original installer check it out periodically and update the system if there are any updates available.

We also have the software to do it ourselves, it is a Zavoli multipoint system.

Peter

Not many,there is one D3 locally with an AJ4.4v8 in it which now runs well since I reflashed the petrol ecu to dumb down the software monitoring Cat performance.I also have a local 4.6P38 with a Romano system one it that has behave very well for about 5 years.
I think there are two main reasons for LPG not being set up properly,firstly because even now few mechanics/techs - call them what you want actually understand closed loop injection and fuel trims.Secondly they rarely bother to spend the time to check everything out about how the engine is running generally - let alone have Testbook or similar running alongside the LPG software to compare the trims on both fuels.This is the only way to do it really,to ensure that the LPG ecu has some chance of mimicking the petrol ecu's thoughts,keeping the fuel trims in check.
It can be done,rarely is....

hi there thanks for the responses. busy busy at work!

the weak spark has been diagnosed with a proper device, I ashamedly forget what its called and double checked with elimination- removing plugs and leads round to see differences.

The problem of misfire/weak spark is only on cylinders 4 and 7 opposing on the same coil and lead from ecu... Thanks RAVE!
it's only been misfiring audibly since the gas conversion and is now the same on both fuels. Ive tested the continuity down the wires to the coil from ecu this afternoon and all is good.

could it be a possible partial circuit breakdown in the ecu?

also car has been back to lpg installer and fuel values checked and all correct although it is still in a learning mode until I have travelled the 4-500 miles required to adjust to the 4.0 as kit was from my old 4.6 which ran very well on gas.

Not sure of plug make but will check asap!

2nd hand ecu connected, coded and still a misfire on 4+7

plugs..have you changed them...i ask as i see no comments on you have

Checking continuity with a multi meter is a good start but a half worn through wire will show up ok
Have you visually checked all wire relating to that coil pack
one good way of checking a wire is a 12v feed and a bulb (If the bulbs bright etc)
stuff has to be disconnected first so you dont put 12v were it shouldnt be and spike something


Just a thought

eightinavee said:

Not many,there is one D3 locally with an AJ4.4v8 in it which now runs well since I reflashed the petrol ecu to dumb down the software monitoring Cat performance.I also have a local 4.6P38 with a Romano system one it that has behave very well for about 5 years.
I think there are two main reasons for LPG not being set up properly,firstly because even now few mechanics/techs - call them what you want actually understand closed loop injection and fuel trims.Secondly they rarely bother to spend the time to check everything out about how the engine is running generally - let alone have Testbook or similar running alongside the LPG software to compare the trims on both fuels.This is the only way to do it really,to ensure that the LPG ecu has some chance of mimicking the petrol ecu's thoughts,keeping the fuel trims in check.
It can be done,rarely is....

Click to expand...

At last - someone who really understands LPG...
The brilliant fitter I used retired, and I got so fed up of the BS from fitters, that I underwent the training to fit it myself. Never looked back.
Yes, it does take time and care to specify, install and set up LPG kit.
The idea that you can do it in a day is for the birds - the setup needs a couple of cold starts at least - for starters.

Anyway, back to the misfire. A few thoughts:-

LPG is harder to ignite than petrol. It's hard on the ignition system.
So, swap leads, coils and plugs - see if the fault follows the part.

Don't assume that something is good - swap it from one cylinder to another, and see if the fault follows it.

If it's a sequential injection system, the injectors can get blocked.
Run some petrol or carb cleaner into the LPG pipe that goes to the injectors - yes, seriously.
If you don't have a low pressure LPG filter the "heavy ends" can block the injector.
Basically, there is a tarry substance left over when you evaporate LPG. There isn't much, but it will build up over time.
Normally, this is caught by a filter in the LPG line.
However, this filter is not always fitted, and these "heavy ends" clag up the solenoid injector.
You sometimes need to wash these tarry deposits out - the easiest way I have found is to undo the injector feed pipe, and pour a couple of tablespoons of neat petrol into this LPG pipe. Then, start the engine on petrol, go for a drive, and change over to LPG at speed. The engine will cough as it over fuels, but the liquid petrol will wash out the. Heavy ends.
My Saab 900 would do this periodically, and this would solve it no worries.
But if you haven't had the conversion long, then this shouldn't be a problem.

LPG doesn't need any fancy spark plugs - it just needs the ignition system to be in very good condition.

And just a thought - run a compression check too... Just to make sure you aren't chasing a mechanical gremlin.

And, if it's been bad since conversion, take it back to the fitter - get him to check it over.

use wd40 instead of gasoline..otherwise i agree.JUST DONE THIS WEEK TO MINE.can use carb cleaner, but beware can kill injector seals, though does a better job.

fill the low pressure lpg pipes up with the stuff, as much as you can get in...BUT dont rev it ..just keep it running till it clears..works wonders..

and who the #### runs lpg without filters!!!!..which will need changing once wd or gasoline used..but at £4 ago no big deal..

Yeah, I wasn't too happy to find no lp filter.

Gasoline or carb cleaner is fine. The LPG seals etc are ok with it.

not according to a well known reputable lpg company...use with caution...wd or equiv is safer and fool proof...(though not quite as effective)

Not come across that advice before.
LPG has very similar hydrocarbon makeup as petrol, and in automotive application, it is a given that any element of the fuel system should be resistant to exposure to petrol and diesel.
For example, it is expected for petrol vapour tobe present in the intake manifold, so the LPG solenoid will need to be resistant to petrol.

Very surprised and worried to learn that some LPG kit manufacturers are not using a suitable material set in their LPG systems.

tinley is the people who suggested i not use ...i trust them...always spot on....and were not trying to sell me nowght

so as they know more dan me on lpg....(though i install.programe my own)..i follow their advice..they were quite insistant upon it, and they know me..(ie know i wont blow up car..lol)

Yeah, I know tinley well, bought a lot of kit from them before I got into the sequential setups.

Suprised that LPG kit seals won't survive petrol...