Mustang Misfire/exhaust leak

[Slum]

Hello guys,recently my brother purchased a 1995 5.0. It has a few things done to it, aluminum heads,cobra intake,fuel pump,pressure regulator,4.10 gears,long tube headers,solid motor mounts and some other stuff.We first noticed a problem when we raced each other at the track in mexico, my stock 2.73 gears,with long tube gt stayed right next to it all the way through.The car does not idle very well,and it seems like its misfiring but could also be an exhaust leak,we have been trying to chase the noise/misfire for a while with not results.The car has new cap,plugs,and wires.The noise follows the engine rpm at idle it happens every 2 seconds or so and the higher rpm the faster,there's no difference between hot or cold engine. Also i checked timing and with spout out its at 14(we run premium) but with spout in the timing jumps a lot never stable. I made a video of the sound at idle to see if anyone with more expertise could help.Thank you

https://www.youtube.com/watch?v=klUpxvvry6I&feature=youtu.be

https://www.youtube.com/watch?v=6EtcVw-613I&feature=youtu.be

 

[CC'S95GT]

With the spout in the timing will jump all over the place because the computer is controling the timing. It's supposed to do that.
With those mods, the engine should have been dyno tuned to optimize those upgraded parts. The alumnium heads and intake flow better but the computer still thinks its stock.

 

[Michael Plummer]

A couple of things.
1) The processor will use 10 degrees of timing to control idle. The more it moves basically means your settings for your idle stop and idle bypass screw and TPS are not set correctly. Now when you say it moves, how much is it moving? If it's moving or jumping around from 20 degrees to 10 degrees back to 18 degrees back to 10 degrees that is not correct.

2) That rapping on the driver's side of the engine sounds like a broken valve spring or something in the valve train. If you don't have the mechanical skills or tools to work on cars I would bring it to a repair shop that does.

Good luck
Michael Plummer

 

[ranger56528]

Yep sounds like a broken valve spring being its not a tick,roller trying to keep pressure on the pushrod,had a 289 with a bad spring and it sounded a lot like that,but ya never know till ya pull the cover.

 

[the5.ohh]

I could be wrong but in the first video, drivers side rear most plug wire looks like its laying on the longtube. That'll cause you some issues.. I have longtubes, same wires and I'm on my 4th set of wires because of them getting burned up