2002 Mustang - Rough Idle Issue

[2002newedge]

Hello,

I have recently been having a rough idle/misfire issue on my 2002 Mustang gt.

The car ran great last year then I pulled the engine and trans to perform some rust repair. When the engine was out I did head gaskets as well as replaced the timing chains and valve seals.

Once the car was put back together I have been fighting these rough running issues ever since.

It seems to be misfiring on cylinders 1,5, and 6. The exhaust smells very rich and when I unplug the COPs for those cylinders there is no change in how it runs unlike the other cylinders. Another thing to note is I get decel pops when I down shift to around 2500 rpm.

So far I have:
Replace the COPs and spark plugs.
Checked compression and was good.
Pulled and bench cleaned/checked injectors and confirmed they were working. Also checked in vehicle.
Rechecked proper timing.
Check for vacuum leaks.

Car engine mods are as follows:
Accufab plenum
Cold air intake
EGR delete
EVAP delete (also disabled in tune)

Any help is appreciated. Not sure what else I can check.

 

[drofdeath]

I had similar issues and found that some of my injectors were leaking vacuum on the port side from old/damaged O-rings. I replaced the O-rings and used lithium grease on them to lubricate the O-rings and help them seal better. It is very easy to damage the O-rings during installation of the injectors into the manifold. On another note, check your fuel trims and see if they are out of whack. It's possible that there may be other issues causing your problem.