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| adam_k |
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heres the story, had an engine change about 2000km's ago... mix and matched parts from the old one on the new block.. and used my old leads and coil-pack, but new plugs.
car was running fine initially, but after a few hundred k's of the run-in, it started mis-firing. did a changeover for another coilpack and it got worse. changed it for yet another coilpack and leads (the standard motorcraft leads), and it stopped mis-firing, till last night. completely randomly driving home, nothing out of the ordinary, pull up at the lights only to have it backfire hard when i accelerated (on gas). the car is pretty much un-driveable on gas as it just keeps backfiring when it misses. on petrol it doesnt backfire, but it is running a little rough under load. my question, is there a reason why its frying coilpacks? could they be getting too much voltage? and is there a point in buying an aftermarket one and seeing if it lasts any longer? any help appreciated, adam |
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| MadMatt |
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You may be getting spark leakage at the plug end of the lead.
I had this and fitted another set of plugs and have no problems now. You may also want to try this....Dielectric grease. ford-lpg-hydrogen-hho-cng-conversions-f44/ba-injected-gas-spark-plugs-t86198.html blownba wrote: The other thing you MUST use on any car with coil on plug and plugs down in the cylinder head is Dielectric grease. This grease will act as a electrical insulator creating a insulation around the plug to rubber boot that would require more than 80,000 Volts for the spark to even think of getting through. This will eliminate the chance of spark leakage that is so common on the BA's which leads directly to incomplete combustion, or as we know it, BACKFIRE!
Smear each coil boot with dielectric grease on the inside of the ends. So where the coil boot goes onto the plug and pull the boot off and smear some where the boot meets the coil too as this is the most common place for spark leakage to occur. Dielectric grease will make a BA plug change complete and guarantee you the best chance at perfect ignition which will result in NO backfires. I do this to all the BA's I put plugs in and I am yet to have a report of a single backfire since I have been using Bosch Double platinum's and dielectric grease.
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| TROYMAN |
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you changed the leads! did you use new leads? or second hand leads?
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| tickford_6 |
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Posts: 6449 Joined: 11th Nov 2004 |
if it's fine on petrol and only miss fires on gas then your gas system needs to be tuned.
what spark plug gap are you using? |
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| adam_k |
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second hand leads, but working on another car, and all with good resistances. it was mainly to diagnose if leads were an issue.
and it misses on both gas and petrol but with petrol the car is at least runnable. gas just backfires every time i accelerate, the plugs were brand new NGK 1.1mm (dual fuel gap) i'll try that di-electric grease tomorow and see how that goes.. fingers crossed, i'm getting sick of this. |
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| misk_one |
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1.1mm is too large a gap for gas...
should be .8mm re gap your plugs before trying anything else as this is most likely the problem
_________________ XG Panelvan |
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| adam_k |
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misk_one wrote: 1.1mm is too large a gap for gas... should be .8mm re gap your plugs before trying anything else as this is most likely the problem i thought 1.1mm was the correct gap for dual fuel au2? i'm still puzzled as to how it all worked perfectly without a single backfire for ~300km's, and then decided to happen randomly. |
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| misk_one |
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sorry i had a boosted setup in my mind for some reason
 gap them to 1mm and see how you go, LPG should always have a slightly tighter gap. either way, its something you can try thats free and is known to help with an engine that has a miss
_________________ XG Panelvan |
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| lil_lincoln |
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test your inlet manifold for any leaks
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| tickford_6 |
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Posts: 6449 Joined: 11th Nov 2004 |
adam_k wrote: misk_one wrote: 1.1mm is too large a gap for gas... should be .8mm re gap your plugs before trying anything else as this is most likely the problem i thought 1.1mm was the correct gap for dual fuel au2? i'm still puzzled as to how it all worked perfectly without a single backfire for ~300km's, and then decided to happen randomly. is the engine earthed to the body properly. about 6 years dad and I rebuilt the engine in his EB, we both over looked the earth strap, it did pretty much what you are suffering from. Your earth may have come loose |
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| adam_k |
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tickford_6 wrote: adam_k wrote: misk_one wrote: 1.1mm is too large a gap for gas... should be .8mm re gap your plugs before trying anything else as this is most likely the problem i thought 1.1mm was the correct gap for dual fuel au2? i'm still puzzled as to how it all worked perfectly without a single backfire for ~300km's, and then decided to happen randomly. is the engine earthed to the body properly. about 6 years dad and I rebuilt the engine in his EB, we both over looked the earth strap, it did pretty much what you are suffering from. Your earth may have come loose i had a look at the earth today, i'm thinking its the earth because i did spray the block black before it got dropped in. i scraped off all i could off the metal but i think there was paint under the braket that the ground was nut was attached to and also in the hole. |
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| adam_k |
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no luck on the earths in the end.
what other sensors could be causing it to do this? |
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| galapogos01 |
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Posts: 1139 Joined: 27th Feb 2005 Ride: Supercharged EF Fairmont Location: T.I. Performance HQ |
Is the ignition timing retarded?
Are the gas mixtures rich enough? Is the balance line hooked up correctly? Jason
_________________ T.I. Performance - Ford Performance Parts & Tuning - J3 Chips & Tuning, Fuel Pumps & Injectors, Camshafts, Haltech ECUs and more! |
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| misk_one |
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i would still try regapping your plugs before looking at other sensors
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| MadMatt |
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Do this at night.
Warm the car up. Hand brake on (chock wheels if needed). Put it in drive and watch for spark leak at the plugs and along the leads.
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