Intermittent Misfire and Hesitation 2002 Discovery V8

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santer
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Intermittent Misfire and Hesitation 2002 Discovery V8

#1 Post by santer » Mon Sep 22, 2014 6:35 pm

I advised someone to post the V8 LPG problem here but they were unable to register so have pasted it in for them

" Has anyone any experience of LPG. I've just bought a 2002 Discovery V8 to play with so I can spend some time getting, and keeping the XJ in top condition. However, the Disco has an intermittent misfire/hesitation (difficult to describe) when running on LPG. It tends to happen when it gets warm and only at lower speeds and revs. When it happens, I can switch it to petrol and it runs ok. Get the speed up to about 50 and switch back to gas and it doesn't misfire until you drop the speed again. The MAF sensor has been changed, as have the plugs and leads. There are no leaks on the intake side that I can find. I am not getting any codes since I've done the plugs and leads although the misfire/hesitation remains. Whilst actually putting the problem down in words on here, it's made me realise that it's seems more than a single cylinder misfire, more like the engine switching off momentarily. If you take your foot off the throttle and replace it, all is ok until it happens again. My thoughts at present are the link between the lpg ecu and the throttle position sensor or the rev counter as I've found a couple of wiring faults on the lpg system which I've repaired. I suppose it could be that a solenoid in the lpg system is switching off and on intermittently. I know there is a solenoid next to the vapouriser, are there any more? Does anyone have any idea of what the problem may be or reckon my way of thinking is on the right track. Any help and advice you can give would be appreciated. "

LPGC
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#2 Post by LPGC » Mon Sep 22, 2014 8:20 pm

Hi, Tempting to jump the gun and start talking about fuel cut-off settings in the LPG ECU, but really we will need more info..

If the gas system is wired to the tps then it is a single point LPG system is that right? Any idea on makes of the gas system components? Writing on the reducer / the ECU?

Simon
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santer
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#3 Post by santer » Mon Sep 22, 2014 8:44 pm

Thanks, have posted it on the other forum

Gilbertd
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#4 Post by Gilbertd » Mon Sep 22, 2014 10:55 pm

LPGC wrote:If the gas system is wired to the tps then it is a single point LPG system is that right?
I sincerely hope not. A 2002 Disco will have a Thor engine.....
'96 Saab 900XS, AEB Leo, sold
'93 Range Rover 4.2 LSE, Lovato LovEco, sold
'98 Ex-Police Range Rover 4.0, Singlepoint AEB Leo, my daily motor
'97 Range Rover 4.0SE, eGas multipoint, a project.....

Proud to be a member of the YCHJCYA2PDTHFH club.

santer
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#5 Post by santer » Tue Sep 23, 2014 8:23 am

" It is a Zavoli multipoint system. Alisei ecu but can't see anything on the reducer "

rossko
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#6 Post by rossko » Tue Sep 23, 2014 9:32 am

Alesei is not wired to cars TPS.
It doesn't sound like the problem is on the overrun, but that might be a red herring - does it idle smoothly? (or as smoothly as on petrol at any rate)
Has he ever noticed dashboard light flicker at time of problem?
Not likely to get much further than random guessing without plugging the system into a laptop and checking a few things.
Elderly Alesei could have a JX type reducer - which would be highly suspect. Look to see if he has the better Zeta type.

santer
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#7 Post by santer » Tue Sep 23, 2014 8:07 pm

Here is the latest reply

" Just read the reply on the page from an installer. It runs as smoothly on gas as it does on petrol. No noticible change to engine running when changing from petrol to gas. Slight dip of revs momentarily when changing other way. No lights come on dashboard when it happens, but rev counter drops momentarily. I have ordered software and leads to plug it in to my laptop "

rossko
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#8 Post by rossko » Tue Sep 23, 2014 11:34 pm

Another chief suspect on an elderly system would be a type 13 pressure sensor, they do go wonky.

Pedro_The_Swift
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Re: Intermittent Misfire and Hesitation 2002 Discovery V8

#9 Post by Pedro_The_Swift » Sat Jul 18, 2015 9:43 pm

could be a frozen regulator,
Disco II 4.6 with Kent H180, and a Tornado chip on OMVL sequential Inj.
Tows a 2T caravan.
Mostly East Coast Australia.

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