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Engine Misfire after plugs, wires, headers


Well-Known Member
April 5, 2003
Reaction score
City, State
Scottsdale, AZ
Year, Model & Trim Level
2009 Mazda 3 Hatchback
Last weekend I installed a set of Torque Monster Headers, E3 Spark Plugs, and Taylor Thundervolt wires. After the install, everything was great. However, last night on my way home from school, I noticed what I thought was an unusual transmission shift from second to third. Also the engine seemed to sound flat and lacked power. I got home and it puttered, backfired, and shook the whole car.

This morning I removed every plug, checked for any unusual wear, which I didn't find, and made sure every plug was securely tightened down. This did not seem to fix anything, as it still backfires, pops, and putters. I also returned the ECU back to stock, which didn't change anything. Checked the wires, everything looks fine. The CEL has not come on at all during this problem (which I was hoping it would so I can figure out where the misfire is coming from)

My next plan of attack is to replace the plugs with the old Autolites I have to see if that changes anything.

Anyone else had this problem before?

Try disconnecting the battery for 10 mins, and reconnect it. Like you said, try replacing the new spark plugs with the old ones. If that doesnt work then it may be one of your coil packs.

I put the Autolites back in and it seemed fine until the engine got up to temperature, then it started misfiring again.

I got fed up with it and took my Mountaineer to an independent repair shop. They said that the wire for cylinder 7 was burnt and that was causing the misfire. Damn. I paid $100 for these wires and they last me 5 days? I assume that it was contacting the header somewhere, but I used those heat socks to prevent that from happening. Oh well.

EDIT: It was actually cylinder 3 that burnt and the wire actually burnt through the heat sock. This weekend I'm planning on re-routing all the wires so it doesn't happen again.