crerar Posted April 21, 2015 Share Posted April 21, 2015 Stock N42 block, P79 head. Factory exhaust with resonator and a Pacesetter exhaust without the muffler. Just the glass pack. It needs a tune. I'm not sure why it's backfiring like that when I rev over roughly 5 grand. Quote Link to comment Share on other sites More sharing options...
bjhines Posted April 21, 2015 Share Posted April 21, 2015 It is only running on 5 cylinders. That is why it is backfiring. You have an ignition problem, likely the spark plug wires. Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 21, 2015 Share Posted April 21, 2015 (edited) Warning - do not watch this video right after watching zredbaron's video - https://www.youtube.com/watch?v=-Dj6LUXdn4E&feature=youtu.be&t=2m10s from here - http://forums.hybridz.org/topic/24798-na-31lhead-camshaft-questions-no-shortcuts-max/page-12 It will hurt your brain. How long have you had the car? Could be several things, in addition to what bjhines said, causing backfiring. I think some people call what yours did, "after fire". Fuel in the exhaust system lighting off. Edited April 22, 2015 by NewZed Quote Link to comment Share on other sites More sharing options...
crerar Posted April 22, 2015 Author Share Posted April 22, 2015 (edited) "NewZed How long have you had the car? Could be several things, in addition to what cgsheen said, causing backfiring. I think some people call what yours did, "after fire". Fuel in the exhaust system lighting off." I've had the car for almost a year. I haven't been able to actually drive it, because of some legal reasons. So I just start it up to try and keep it in "working" condition. I'm going to check the plugs and wires tomorrow and start it up to see if I can figure out what is wrong. It was doing the same thing with the muffler that comes with the Pacesetter cat back kit on. I was thinking it was causing "after fire" as well. I was hoping that removing that, and putting a straight pipe on and just running the resonator and glasspack, would solve the issue. The PO did install Taylor wires and NGK spark plugs. Along with an MSD blaster coil. I believe he got most of the parts for this car from MSA. No complaints about his work though. Seems to be a decent guy. Edited April 22, 2015 by crerar Quote Link to comment Share on other sites More sharing options...
NewZed Posted April 22, 2015 Share Posted April 22, 2015 It can be caused by an exhaust leak and extra fuel. The missing ignition (if you're lucky, it's an ignition problem, could be a cam lobe) on one cylinder is probably passing unburned fuel, the exhaust leak supplies oxygen. The P79 exhaust liners are designed to burn any fuel that exits the cylinder. One possibility. Is it still EFI? P79 on N42 is not stock. What else has been modified? Best to just get it running on all six first. You can pull injector connectors to find the dead cylinder. Quote Link to comment Share on other sites More sharing options...
crerar Posted April 22, 2015 Author Share Posted April 22, 2015 "Is it still EFI? P79 on N42 is not stock. What else has been modified?" Yes it is still EFI. I am aware that the head is not stock. But as far as I know the block and internal parts are. I adjusted the spark plug gap all of them were over .035, I noticed that one was really easy to loosen. Almost like it was hand tight. I probably got in a hurry. Going to start it up and try to find the issue today. Quote Link to comment Share on other sites More sharing options...
crerar Posted May 30, 2015 Author Share Posted May 30, 2015 Replaced plugs, wires, Distributor cap, and rotor. No more missing, but still backfiring. Will check timing when I get back in town. Quote Link to comment Share on other sites More sharing options...
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