4.6 misfire no codes

[Nickmustangfps]

my 2007 mustang gt has been running rough for years with no codes. Originally I replaced the coil packs and it ran great for about a day then started to misfire again. Shop told me it was because of a bad alternator frying the coils but by the time I replaced the alt and coils again it didn’t help. I’ve replaced just about every part (coils, plugs, injectors, o2s, pcm, wire harness, cam solenoids, full exhaust, battery, timing assembly, piston rings, and had the heads checked) mechanically the engine is fine with full compression so idk what the issue is. I did notice the wire connection to the driver side coils read 11-12 volts when running but the passenger side all reads 14. Neighbor said it should be fine bc the coils up the voltage significantly but that voltage drop seems to be the only thing off in diagnostics. Additionally the car feels sluggish and can only go 0-60 in 6.5 secs at its best. (Stock should be 5.2) PLEASE HELP

 

[07 Boss]

No codes so you gotta look where the car can’t detect an issue. Looks like we have covered fuel and spark. Let’s look at air. Maybe charge motion plates are gunked up. Have you checked for full throttle body movement. Or on the flip side maybe clogged cats. Maybe pull the valve covers and crank the engine by hand and verify all followers and valves are functioning properly. Have you done any data logging? Maybe your timing is off. Could be so many things, don’t know where to start without some kind of code.

 

[Nickmustangfps]

The charge motion plates and tb look good and open and close fine. The cats are brand new so shouldn’t be clogged. I also ran it open header to see if there were any difference but no difference other than deafening myself. I checked all roller followers, springs and had the heads checked by a machine shop. I took the car to the shop a few weeks ago to see if they could find anything, they ran a few tests like compression leak down and it looked perfect but they said I needed to change plugs back to motorcraft. They got new plugs in and the power band did improve a bit but not at fully power. Very unfortunate especially because they charged me $1100. P0420 is on for catalytic inefficient but all sensors are new and same with cats. I don’t know where to start or what to look for with data logging. I can probably figure it out if I knew what to set the log for.

 

[john knox]

try forscan.org software the ecu ctl all of it, see in the pic no mil lamp, but ecu was smoked ran like shit, if your going to own mustang get this software

 

[Nickmustangfps]

Thanks, I’ll let you know how it goes

 

[moooosestang]

Clean all the grounds if you haven't all ready! Add an additional ground from motor mount to frame rail. I used one of the wire loom holes in the frame on the passenger side and just threaded in a self tapping bolt that came off the car some other place. Installed a 4awg ground wire there just to be sure the motor is well grounded. There's a braided ground strap coming off the back of the drivers side head going to the firewall. That ground never really sat well with me. The firewall is super thin metal there. Clean the grounds for the fpdm in the trunk. Basically if you see a ground wire, remove it, sand it, reinstall it with some kind of dieletric grease wouldn't hurt.

 

[moooosestang]

tried to show where i added the extra engine ground, but it's hard to see. Seems i used 1awg for it because i wanted all the cables from battery to starter to be the same size, but that's overkill for the ground wire. I hope you replaced the alternator with a 2010 or a pa performance. Any of the reman alternators are junk!

 

[86GT351]

What scanner are you using?

 

[Nickmustangfps]

Using the sct x4 from bama but I recently tried plugging it into my laptop for the forscan software but the connection broke now I’m waiting for the new wiring