ThreeSheds Posted September 10, 2009 Share Posted September 10, 2009 Mystery misfire poses problematic symptoms - solution satisfactorily simple: Proper plug-ins prevent pss poor performance... I got a mystery misfire (I think it was running on 6/8) after hundreds of miles of great running since getting the RRC back on the road. It occurred at all times but got MUCH worse (not drivable) when on petrol and giving it some berries, when it would splutter and not pull at all. Gas on a wide throttle was reasonable (still misfiring but drivable). Since the misfire was worse on petrol than gas (which is unusual since gas is harder to light-up than petrol) - and after checking and gaps/condition of all plugs and HT and LT ignition wires etc I concluded that the MegaJolted ignition was fine and that it must be fuel. Next step - checked all temp sensors, fuel pipes/pump/flow/pressure/return, injector wires, ECU connections, fuel pump and injector relays. Everything except the actual injectors - at this stage I didn't want to strip that far down) All fine. BUGGER! Then - sitting in the cab listening to it misfire, scratching my ass trying to think (I find it helps), I noticed that the plug on the 'four diodes and a zenner' flyback circuit was not quite home (it sits on the dash) and so I absent-mindedly pushed it in - only two millimetres and... INSTANT smooth runnings. So - why was it worse on petrol than gas? Only thing I can think of is that the 14CUX was detecting the misfire and going into limp-home or something and refusing to give full volumes of fuel... Anyone know if it does this? (there are no lambdas on mine so it's not 'seeing' the unburnt fuel at all...) Still confused but happy it's fixed Quote Link to comment Share on other sites More sharing options...
RangeyRover Posted September 14, 2009 Share Posted September 14, 2009 Mystery misfire poses problematic symptoms - solution satisfactorily simple: Proper plug-ins prevent pss poor performance... I got a mystery misfire (I think it was running on 6/8) after hundreds of miles of great running since getting the RRC back on the road. It occurred at all times but got MUCH worse (not drivable) when on petrol and giving it some berries, when it would splutter and not pull at all. Gas on a wide throttle was reasonable (still misfiring but drivable). Since the misfire was worse on petrol than gas (which is unusual since gas is harder to light-up than petrol) - and after checking and gaps/condition of all plugs and HT and LT ignition wires etc I concluded that the MegaJolted ignition was fine and that it must be fuel. Next step - checked all temp sensors, fuel pipes/pump/flow/pressure/return, injector wires, ECU connections, fuel pump and injector relays. Everything except the actual injectors - at this stage I didn't want to strip that far down) All fine. BUGGER! Then - sitting in the cab listening to it misfire, scratching my ass trying to think (I find it helps), I noticed that the plug on the 'four diodes and a zenner' flyback circuit was not quite home (it sits on the dash) and so I absent-mindedly pushed it in - only two millimetres and... INSTANT smooth runnings. So - why was it worse on petrol than gas? Only thing I can think of is that the 14CUX was detecting the misfire and going into limp-home or something and refusing to give full volumes of fuel... Anyone know if it does this? (there are no lambdas on mine so it's not 'seeing' the unburnt fuel at all...) Still confused but happy it's fixed 14cux needs to know revs from the coil to sort the fuelling. It wont run on petrol with it disconnected. On gas you are really run like a carb engine, as the fuel mix has already been done, so the 14cux has little influence on the engine when there is something to ignite. Quote Link to comment Share on other sites More sharing options...
ThreeSheds Posted September 14, 2009 Author Share Posted September 14, 2009 It wont run on petrol with it disconnected. Yes - I subsequently proved that by pulling it right out - what was confusing me is that it was running at all when on petrol! Thinking further on it I believe that some of the pulses were not getting through (the plug was kind-of half out and at a slight angle) and possibly the 14CUX thought that the revs were lower than they actually were and hence was under-fuelling. Anyway - she's back to being a beaut again Quote Link to comment Share on other sites More sharing options...
Thunderkatt Posted September 19, 2009 Share Posted September 19, 2009 Glad to see your up and running again m8 Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.