Dr W Posted January 19, 2009 Share Posted January 19, 2009 Hi guys Hope you can give me some advice on my Classic 1992, 3.9 V8, lpg/petrol. It's got lpg so within the last year I've fitted A&R Power amp, ignition amplifier Magnecore HT leads New rotor arm New coil (last one died) My Classic has recently developed an interesting problem. I have to go out on a saturday morning and drive 22 miles which car does no problem, however when I drive back home towards the end of the journey say last mile when I hit a bit of traffic it starts to misfire to the point that if I put my foot down it spits and bangs, if I gently press the accelerator I can creep along but no hard pressing. I thought it might be the HT leads so switched engine off wiggled leads and restarted and it seemed ok but then a few mins later same problem will happen. If I swtich off and back on then it's ok for a while. I then leave the car for a week and chance it again, the journey down is fine but back it happens again. I did a 30 mile journey during the week and it was fine for the whole journey. I've tried switching between lpg and petrol but no help. What I can't figure out is why it's happening when the engine is hot. I thought it might be fuel issue but then surely switching between fuels would resolve this. I hope someone on here might have some ideas on how I can locate problem as it's driving my daft and makes me a bit worried to do long miles as dono't know when it's going to happen. Many thanks Dr W Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted January 19, 2009 Share Posted January 19, 2009 You don't say anything about the plugs.....? If you haven't changed them then stick a set of NGK BPR6ES in it and try again Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 19, 2009 Share Posted January 19, 2009 The traditional misfire when hot is ignition amp, especially if it's the same on petrol or LPG. Quote Link to comment Share on other sites More sharing options...
Dr W Posted January 19, 2009 Author Share Posted January 19, 2009 The traditional misfire when hot is ignition amp, especially if it's the same on petrol or LPG. If you think it's the ignition amp what do you think I do about it? Can it be adjusted or does it need replacing? Going to try replacing the plugs and rotor arm this weekend and see if that improves it. The problem is the misfire is not constant and happens irractically so difficult to trace. Thanks Quote Link to comment Share on other sites More sharing options...
DC_ Posted January 19, 2009 Share Posted January 19, 2009 Ignition Amp is on the side of your distributor (dizzy) These can fail due to heat penetration so best bet would be to fit a new one. Not that expensive, but if your really a doctor then that shouldn't matter to you Make sure if your replacing the Rotor arm, that you do so with GENUINE parts ONLY !!! The pattern ones are no good and will cause you more headaches my friend. DC Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 19, 2009 Share Posted January 19, 2009 The A&R amp isn't on the side of the dizzy, it's a separate magic box from RPi and they don't appear to have the best reliability record. I'd ditch it and go to MegaJolt, that way you can have two proper spark maps rather than whatever-the-dizzy-is-plus-a-bit. Similar money too, from memory. Quote Link to comment Share on other sites More sharing options...
Dr W Posted January 20, 2009 Author Share Posted January 20, 2009 No I'm not a doctor so pennies do matter (that's why I drive an old Classic as my everyday car and not a brand new Vogue. Rpi tell me that they have no problems with the Power Amp other than total failure in a few cases and that reliability is high. Not sure how I would know if the box failed anyway? Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 21, 2009 Share Posted January 21, 2009 Rpi tell me that they have no problems with the Power Amp other than total failure in a few cases and that reliability is high. RPi say a lot of things I would suggest working through the V8 EFI fault-finding guide in the tech archive and seeing what you find. Quote Link to comment Share on other sites More sharing options...
Dr W Posted January 21, 2009 Author Share Posted January 21, 2009 RPi say a lot of things I would suggest working through the V8 EFI fault-finding guide in the tech archive and seeing what you find. They seem to know their stuff though. I'll have a look at that tech guide you suggested, Cheers Quote Link to comment Share on other sites More sharing options...
Thing Posted January 21, 2009 Share Posted January 21, 2009 i had one of these rpi amps and there carp! had the simler problem on my rrc stuck the orignal amp back on the side of the dizzy and set it slightly advance and hey presto problem solved! lol Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 21, 2009 Share Posted January 21, 2009 They seem to know their stuff though. Some of their advice does collide with reality in places, yes. More often than not though, it's about selling you stuff. Quote Link to comment Share on other sites More sharing options...
Dr W Posted January 22, 2009 Author Share Posted January 22, 2009 Hats off to you Fridgefreezer, garage I took car to for it's service (Quadratech) and have a look at the problem told me that the Power Amp was the problem. Now most of stuff about dwell etc goes over my head but what they said was that there was 40 degrees dwell (?) and that the coil wasn't having time to cool down and so the coil was running at 120 degrees C. They disconnected the Power Amp and car started running ok again with amp running about 50 degrees C. I had a coil go on me about 4 months ago and the garage said that it was probably the Power Amp that caused the old original coil to burn out. RPi tell me that the power amp only amplifies the spark (to make the LPG burn more efficiently) and that removing the amp doesn't solve the problem it just releases the pressure a bit so everything appears to be working properly. They said it was that most old classics are running on worn inefficient distributors and replacing this would might remove the problem and enable the Power Amp to work properly? To be fair they did offer to look at the amp and test it if I sent it back or have a look over the car but Norfolk is a bit of a trek. I have to say that replacing HT leads, rotor arm, fitting the power amp and a new vapouriser (old one had a hole in it) did help to increase the MPG from 10 to 20 on a motorway run. Can't say any one part helped more than the others but I may just run it around for a while and do some motorway miles to see if the mpg drops after removing the amp. What's the Megajolt thing you mentioned in an earlier post? How does it work? Quote Link to comment Share on other sites More sharing options...
bobtail84 Posted January 22, 2009 Share Posted January 22, 2009 What's the Megajolt thing you mentioned in an earlier post? How does it work? Megajolt is half the job Mega squirt is the full fat version. Read this and it may help... Mega Squirt Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 22, 2009 Share Posted January 22, 2009 Sounds like RPi blowing smoke up your behind, if the amp was pukka it would work OK with all the stock bits. I still vote for MegaJolt or squirt. Quote Link to comment Share on other sites More sharing options...
Dr W Posted January 22, 2009 Author Share Posted January 22, 2009 But from what I read on the Megajolt thread there isn't any point if I'm running on gas 99% of the time. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 22, 2009 Share Posted January 22, 2009 But from what I read on the Megajolt thread there isn't any point if I'm running on gas 99% of the time. Not quite, there isn't any point going MegaSquirt if you rarely run on petrol but going to MegaJolt for the ignition is a good idea. Quote Link to comment Share on other sites More sharing options...
Dr W Posted January 23, 2009 Author Share Posted January 23, 2009 Not quite, there isn't any point going MegaSquirt if you rarely run on petrol but going to MegaJolt for the ignition is a good idea. OK thanks maybe I'll look into it. Do you buy it as a kit? How much is it? Is it easy to fit and finally where can you buy it? Cheers Quote Link to comment Share on other sites More sharing options...
steve_d Posted January 23, 2009 Share Posted January 23, 2009 OK thanks maybe I'll look into it.Do you buy it as a kit? How much is it? Is it easy to fit and finally where can you buy it? Cheers You can buy a kit or built. See the 'For sale' section as there is a guy on here sells them. You will then need to fit a trigger wheel to the back of the front pulley and a VR sensor (ex Ford Escort) to point at the trigger wheel. Then a Pair of Escort coil packs plus mounting brackets. What has not perhaps been explained to you is that Jolt can run different ignition maps for each fuel as they each like there spark timed differently. Also be warned the Ford coil packs produce monster sparks which will do you no good if you get too close. FF has a picture somewhere of a coil pack in full Guy Fawkes mode. Steve Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted January 23, 2009 Share Posted January 23, 2009 You mean this one? Quote Link to comment Share on other sites More sharing options...
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