P38R

[stuart1wba]

Hi, I am P38R [Stuart Humphries] with a P38 HSE 4.6 Petrol/LPG. Love it!
Can you help make her well again please?
HELP!
issue:
hesitancy on acceleration like fuel being switched on and off - not selecting gear properly.
lack of power generally, worse uphill!
too much acceleration i.e. towards "kick down" and it pops!
replaced plugs and leads - no change!
replaced air filter box - no change!
diagnosed inoperative air flow meter.
replaced air flow meter
took on run, hilly and flat -
that's better...no, hesitation again, albeit once.
on level went for kick down - BANG!
air box blown, air flow meter wire mesh found on top of air filter.
If it's none of those........HELP!
Stuart.

[jacckk]

I'm guessing you have a single point LPG system since it's blowing the airbox?

How does it run on petrol, if it doesn't run well on petrol it's never going to work on LPG. I'd try running it on petrol for a bit to give the ECU time to adapt to that and see what it's like then.

[paintman]

What LPG system & how is the vapourised gas introduced into the inlet?
If its single point - and if the flashback is on LPG I suspect it is - the symptoms you give are usually caused by a weak mixture.
As asked, does it run without issue on petrol? If it doesn't then that needs to be sorted first.

[Jimmyarm]

Check the TPS resistance curve is correct and the input and output voltages are right.

[calibrax]

I hate it when people come on and quote model designations instead of actual car names. Not everyone is at your level of anorak. It's bad enough with BMWs, but now Range Rovers?

[Jimmyarm]

calibrax said:

I hate it when people come on and quote model designations instead of actual car names. Not everyone is at your level of anorak. It's bad enough with BMWs, but now Range Rovers?

To be fair, it is a car enthusiast site and I expect most people on here know what a P38 is

[lbc]

calibrax said:

I hate it when people come on and quote model designations instead of actual car names. Not everyone is at your level of anorak. It's bad enough with BMWs, but now Range Rovers?

I had a couple of P6 Rover's many years ago.

It's the only real language of knowing what is being discussed.

[Leptons]

Jimmyarm said:

To be fair, it is a car enthusiast site and I expect most people on here know what a P38 is

To be fair anyone who doesn't know what a P38 is should hand their membership in on the way out.

[calibrax]

Leptons said:

Jimmyarm said:

To be fair, it is a car enthusiast site and I expect most people on here know what a P38 is

To be fair anyone who doesn't know what a P38 is should hand their membership in on the way out.

To me, P38 is a filler. Which is car related.

[P38R]

jacckk said:

I'm guessing you have a single point LPG system since it's blowing the airbox?

How does it run on petrol, if it doesn't run well on petrol it's never going to work on LPG. I'd try running it on petrol for a bit to give the ECU time to adapt to that and see what it's like then.

Hello jacckk.
I believe it is a single point LPG system.
I have had the issue with both fuels.
When engine is cold it runs well...
I will run on petrol [for as long as I can afford it. lol] and let you know.
Thank you.

[cars1993]

If its the LPG system type which has a pipe feeding the manifold and not the injectors directly then that's possibly your problem. By putting your foot to the floor chucks all the gas in, it doesn't burn properly it fills the cat with gas and then it explodes underneath you which can damage the cat.

Same thing happened on my dads P38 had the same system. That system is designed for the RR classic with the carb system not the injection system.

[jacckk]

If it's running well when cold I would probably suspect that your fuel trims are messed up and when it's cold it ignores the fuel trims/oxygen sensor readings.

Have you had the fuel trims reset when you found the bad airflow meter? They could have caused them to What I would do is get the trims reset, run it 100% on petrol for a tank and then take it to an LPG installer to sort out the LPG side.

[P38R]

paintman said:

What LPG system & how is the vapourised gas introduced into the inlet?
If its single point - and if the flashback is on LPG I suspect it is - the symptoms you give are usually caused by a weak mixture.
As asked, does it run without issue on petrol? If it doesn't then that needs to be sorted first.

Hi paintman
I believe it is a single point inlet.
Issue is with either fuel but I am told LPG will cause the "bang".
The timing was reset but I still had the issue. The follow up was a computer check - air flow was not registering.
Next move is to replace the air sensor again but check the air flow reading BEFORE I run it, not likely to be a solution but will confirm the sensor is good.
I will a suggestion from 'jacckk' to run on petrol only for a while to let things settle.
Will keep you posted.
Thank you.

[P38R]

Jimmyarm said:

Check the TPS resistance curve is correct and the input and output voltages are right.

Hi jimmyarm.
Don't know what that is but will certainly go for it and let you know.
Thank you

[P38R]

cars1993 said:

If its the LPG system type which has a pipe feeding the manifold and not the injectors directly then that's possibly your problem. By putting your foot to the floor chucks all the gas in, it doesn't burn properly it fills the cat with gas and then it explodes underneath you which can damage the cat.

Same thing happened on my dads P38 had the same system. That system is designed for the RR classic with the carb system not the injection system.

Hi cars1993.
Good point and will follow up, but how do find the root cause i.e. why did it start doing what it's doing it in the first place?
Keep you posted.

[Denis O]

calibrax said:

Leptons said:

Jimmyarm said:

To be fair, it is a car enthusiast site and I expect most people on here know what a P38 is

To be fair anyone who doesn't know what a P38 is should hand their membership in on the way out.

To me, P38 is a filler. Which is car related.

It's hardly likely he was talking about a pot of pug though, was it?

[Fastdruid]

Jimmyarm said:

calibrax said:

I hate it when people come on and quote model designations instead of actual car names. Not everyone is at your level of anorak. It's bad enough with BMWs, but now Range Rovers?

To be fair, it is a car enthusiast site and I expect most people on here know what a P38 is

Type of plane isn't it?

[paintman]

I gassed my 3.5EFI RRC around 15 years ago. Initially a gas ring type inlet but replaced a few years ago with a BLOS LPG carburettor. For single point the BLOS is very good indeed. This ebay ad shows one fitted to a 3.9 RRC - exactly as its fitted to mine which is the older flapper type air flow meter.
http://www.ebay.co.uk/itm/BLOS-Propane-Carburetor-...
I do have a flashback arrester fitted & it has saved me on a couple of occasions - each of which were entirely my own fault.
The Classic - either carbs or EFi - is OK with single point.They DON'T need emulators - contrary to what some sellers will try & tell you. The P38 isn't really suited to single point systems & is better with sequential injection systems. Later RR models should be sequential only due to their electronics.
LPG doesn't like problems in the ignition system & all leads, plugs, rotor arms, dizzy caps, coil packs etc need to be of good quality and in good condition.

The flashbacks you are getting are more common with a single point system. It is nothing whatsoever to do with loads of gas being chucked in, not being burnt in the cylinder & going bang in the exhaust - its the exact opposite. The explosion is occurring inside the inlet side - manifold, plenum chamber, air flow meter, filter housing & associated pipework.
When on petrol there is no explosive mixture in the plenum chamber but when on single point LPG, due to the position of the gas ring, the plenum will have a mix of LPG & air which is then drawn into the cylinders.
A danger point with single point is when the LPG is running low as a 'foot down' will give the perfect scenarion for a flashback. Switching manually from petrol to LPG should be done on a trailing throttle (foot off) for the same reason.

Your priority is to get it running without issue on petrol. Once that's sorted then look at the LPG.

Edited by paintman on Tuesday 16th September 18:55

[s p a c e m a n]

Does it have 14cux or gems ecu? There's a diagnostics program that will show you all error codes/lambda readings ect for the 14cux..

https://code.google.com/p/rovergauge/

You can buy the cable to connect the ecu to a laptop and a copy of the program on a disk in the classifieds here..

http://www.pistonheads.com/classifieds/parts-and-p...

Here's the thread about it..

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

[P38R]

s p a c e m a n said:

Does it have 14cux or gems ecu? There's a diagnostics program that will show you all error codes/lambda readings ect for the 14cux..

https://code.google.com/p/rovergauge/

You can buy the cable to connect the ecu to a laptop and a copy of the program on a disk in the classifieds here..

http://www.pistonheads.com/classifieds/parts-and-p...

Here's the thread about it..

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Thanks spaceman. It is a Gems engine!