 | Home > V8 > Misfires are back! |
 
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| charcoal Member Since: 28 Jul 2014 Location: Hampshire Posts: 942   
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I don't think so, I thought the revs were only limited by how fast the tappets and valve springs can run? How would I identify a rev limiter? 1999 Land Rover Defender 110 td5 station wagon
1998 Land Rover Defender 110 County Station Wagon ~ Sold 1995 Land Rover Defender 110 V8 Station Wagon ~ Sold 
1985 Land Rover 110 ex mod project Tithonus ~ Sold |
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12th Dec 2016 4:56pm |
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| muddypaws Member Since: 22 Jan 2013 Location: Leicestershire Posts: 122  
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Usually a little black aftermarket box about the size of a matchbox with a couple of wires heading onto the coil
Mine started to malfunction after a winter hibernation & instead of kicking in at 6.5K, it started working at 1.8K & caused no end of head scratching. Richard Defender 90 SVX |
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12th Dec 2016 7:29pm |
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| muddypaws Member Since: 22 Jan 2013 Location: Leicestershire Posts: 122
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here's the one I had Richard Defender 90 SVX |
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12th Dec 2016 7:32pm |
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| charcoal Member Since: 28 Jul 2014 Location: Hampshire Posts: 942
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Ah, I have nothing like that. Maybe it was only fitted to sporty type cars? 1999 Land Rover Defender 110 td5 station wagon
1998 Land Rover Defender 110 County Station Wagon ~ Sold 1995 Land Rover Defender 110 V8 Station Wagon ~ Sold
1985 Land Rover 110 ex mod project Tithonus ~ Sold |
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13th Dec 2016 12:07am |
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| muddypaws Member Since: 22 Jan 2013 Location: Leicestershire Posts: 122
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Just a thought......
BTW no one has mentioned the rotor arm yet; crack in it, poor connection on pillar etc I believe it still sounds electrical not fuel - esp if the age old trick of a little choke when it is happening makes no difference Richard Defender 90 SVX |
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13th Dec 2016 7:36am |
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| charcoal Member Since: 28 Jul 2014 Location: Hampshire Posts: 942
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The rotor arm was replaced along with the distributor body the other month and made no difference. That's what was making me think it was electrical too but I've replaced every electrical component now and nothings been solved.
 1999 Land Rover Defender 110 td5 station wagon
1998 Land Rover Defender 110 County Station Wagon ~ Sold 1995 Land Rover Defender 110 V8 Station Wagon ~ Sold
1985 Land Rover 110 ex mod project Tithonus ~ Sold |
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13th Dec 2016 11:58pm |
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| muddypaws Member Since: 22 Jan 2013 Location: Leicestershire Posts: 122
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Hmm....can you reproduce the misfire when not under load?
I attached a strobe light to the leads in turn, then produced the misfire by reving whilst stationary. This way you can find out if it is the HT circuit ie king pin, or individual leads. Of course if no misfire when stationary then you cant Richard
Defender 90 SVX |
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14th Dec 2016 8:38am |
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| charcoal Member Since: 28 Jul 2014 Location: Hampshire Posts: 942
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Can't reproduce it without load
Sometimes when if it's bad enough you can pull over and it's still misfiring but by the time you got a timing strobe set up it would be back to normal. 1999 Land Rover Defender 110 td5 station wagon
1998 Land Rover Defender 110 County Station Wagon ~ Sold 1995 Land Rover Defender 110 V8 Station Wagon ~ Sold
1985 Land Rover 110 ex mod project Tithonus ~ Sold |
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14th Dec 2016 11:00am |
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| muddypaws Member Since: 22 Jan 2013 Location: Leicestershire Posts: 122
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Its starting to sound more fuel related I reluctantly admit although that wouldn't cause the backfire you describe.
What is strange is that the RV8 is such a forgiving engine in such a low state of tune, I'm amazed its misfiring; my old RV8 put out 325bhp & when it wasn't fuelled right, it was just be slower but never misfired (except when I mistimed the dizzy  & also had the rev limiter issue) Richard
Defender 90 SVX |
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14th Dec 2016 12:20pm |
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| ian series 1 Member Since: 17 Nov 2014 Location: south Posts: 3127 
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Have you had a go at running a tempory fuel feed?
5ltr can sat on wing or bonnet straight into carbs... 80" 80" 86" 88" 90" Wanted, Forward Control Anything considered. |
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14th Dec 2016 1:18pm |
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| charcoal Member Since: 28 Jul 2014 Location: Hampshire Posts: 942
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The recent backfires sound like exhaust ones, they are quite quiet compared to the one I described in detail which must've been an intake one. Could be normal as I heard they can do that while accelerating at cold temperatures? I haven't hooked it up to a temporary fuel source, why would I need one? 1999 Land Rover Defender 110 td5 station wagon
1998 Land Rover Defender 110 County Station Wagon ~ Sold 1995 Land Rover Defender 110 V8 Station Wagon ~ Sold
1985 Land Rover 110 ex mod project Tithonus ~ Sold |
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16th Dec 2016 12:12am |
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| Morepower Member Since: 08 Jan 2013 Location: Fife, Scotland Posts: 630 
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Hi Charcoal...
Sounds like your fighting some serious issues there... In my experience, This could be down to a few things... Your timing could be jumping around... or you have a seriously lean mixture... or very rich... Reading back, you say it's been on a rolling road... I would suggest going back and trying to emulate the issues... You should be able to see the timing moving if thats the issue with a strobe whilst it's under load and the lambda will give you a good idea of where the mixture is... Although I would recommend also running a HC meter to analyse how the mixture is burning as Lambda sensors can invert in the extremes... I.e dangerously lean can look rich and vise versa... However, any good dyno operator should know this, and usually the figures will tell the story, too lean and the graph will look raggy, like wise for too much advance... Hope this helps Regards Tim It doesn't matter how bad it is, It can always get worse... 2013 Bowler 110 (Sold) 2016 Bowler 90 Rally Spec (Sold) |
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16th Dec 2016 6:43am |
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| GREENI Member Since: 22 Aug 2010 Location: staffs Posts: 10383
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I'm still intrigued to what's wrong. Everything is all bolted up tight? Headers, inlet manifold, etc etc.
Alex who owns Staffs 4x4 is pretty much a v8 guru, we had a TVR in that wouldn't run right, it went to a few garages before coming to us and he quickly diagnosed the plenum was not sealed right and once sealed, ran fine. |
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16th Dec 2016 6:54am |
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| ian series 1 Member Since: 17 Nov 2014 Location: south Posts: 3127
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It would eliminate any fuel supply problems from the tank to the carbs. At least then you know for sure it's not anything related? And you can move on to the engine itself. 80" 80" 86" 88" 90" Wanted, Forward Control Anything considered. |
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16th Dec 2016 7:14am |
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