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Discussion Starter · #1 ·
I just wanted to get some feedback and ideas from expirenced members on the board. A few months ago I attempted a tach light install using an msd tach signal. The tach sender reqiuired cutting one of the ignition wires (i picked the wire going to the coil on cylinder 4). In any event, the install failed because i realized the tach light i used could only be used on 4-6-8 cyl, and was not setup to just read the signal from one cylinder. We soldered the ignition power wire back together, unfortunately using a diff wire to extend the wire a little bit because it lost a little length during the original splicing. I began to have misfires on that cylinder about two weeks later, when the car felt like it was only running on three cylinders periodically, and this was confirmed when i finally threw a cel which stated misfire cylinder four. I brought it to my local mazda dealership who confirmed as well I was having misfires, and suggested that I replace the wiring harness because since it was cut, it was no longer under warranty. They stated that it was happening due to the wire we had used to extend the wire a little bit, because the resistance in that bigger gauge wire was higher than the oem wire. So i believed if i just brought the car home and soldered the oem wire back together without the higher gauge inbetween, it would function properly. I was wrong, it ran good for about two hours but then began to misfire again. I discussed this with a friend of mine who works as a machanic at a local bmw dealership, and he suggested that the coil might have gone bad due to the original misfires and improper resistance in the wire. So with this in mind, I replaced the coil for cylinder four, and all four spark plugs (just incase the one in cylinder four had been fouled). Now, as it stands now, my ignition wire is soldered back together, and in my mind it should be operating just as an OEM ignition wire would be without being spliced, and I also have a brand new coil and sparkplug for this cylinder. The problem is I am still left with the original problem i started with, I have multiple misfires in cylinder 4, confirmed with more cel's thrown, and it seems to get a little worse once the car has warmed up completely. My question to the expirenced people on this board, is it really possible for the resistance to still remain off (as in not the same as a brand new ignition harness or engine harness) just because of the soldered connection before continuing into the wire and into the coil? I've never really seen an electrical current chance enough to notice a difference because of a soldered connection, especially if the wire that was soldered back together was the OEM wire. Any ideas? So far I have either figured that it is making that much of a difference... which supprises me... or possibly a bad ecu? Any suggestions or help would be very much appriciated. The cell I am repeatedly getting from the misfire is (P0304 Cylinder 4 misfire), and initially because I had soldered the wire back to how it was, and pre-coil and sparkplug replacement, i had a P0442 Evap emissions control system leak along with the cylinder 4 misfire code, but have since not seen the evap code again... :boom:

Edit: BTW this is on a 2007 Mazdaspeed3, Only mod is a Mazdaspeed CAI.
 

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maybe its just the time to change the sparkplugs ?
 

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Discussion Starter · #3 ·
[quote author=Bounty44 link=topic=140458.msg3027656#msg3027656 date=1238449211]
I replaced the coil for cylinder four, and all four spark plugs (just incase the one in cylinder four had been fouled). [/quote]

Done it.
 

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Go to a junkyard and get a coil wire and try splicing it in, you may have inadvertantly broken a connecton in that end. I do not think the resistance change is critical in that low voltage circuit.
 
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