2003 Pontiac Aztek, 3.4L/4T65E, 135,xxx miles.
Compliant.....Misfire on #5 cylinder. Coils, ICM, Plug Wires, & Spark Plugs have been changed by another shop/mechanic.
It is indeed misfiring on #5 cylinder, LT Fuel trims are hovering @ negative 6% at idle.
Balance tested all 6 injectors, They were within 2% of each other.
Vacuum gauge was steady but low @ 14 inches.
Disabled spark & cranked the engine over, This revealed an uneven compression issue by the sound.
Called the customer & got the okay to pull the Bank 2 (rear) valve cover, Back off the rockers & do a Leak Down test on #5.
Pulled the cover & found the #5 Inlet Rocker laying on it's side. Threads pulled out out of the head, Pushrod was sitting off the lifter but was able the retrieve it with a pencil magnet.
I made the decision to Heli-Coil it blind using a mirror & flashlight. I drilled the hole out by hand using a Tap T-Handle tightened onto a 21/64" drill bit, Was able to watch the angle compared to the #3 Inlet Rocker bolt while drilling & tapping for the Heli-Coil insert. Used liberal amounts of wheel bearing grease on the tooling to catch most of the aluminum chips/debris.
Loctited the insert in & let it sit overnight, Broke the insert drive tang off with some hemostats, Ran in a thread chaser to clean out the left over Loctite, Torqued the Rocker Arm assembly down to spec. Barred the engine over & confirmed the Rocker had a little side to side movement (The lifter didn't stay pumped-up).....The lifter didn't want to bleed down by simply torquing the rocker.
Engine now runs on all 6 cylinders, Let it run to operating temp & change the oil & filter.
The Rocker threads were pulled during a LIM gasket change that was done by the same shop that sold all the tune-up parts. I checked the other rocker arm bolts on the rear bank...They held torque after back them off a little. Customer stated the engine ran fine for a couple weeks after the LIM gasket job.
Please don't ask about the cost, It's probably more than you think it's worth, There are no book times for fixing screw-up's that shouldn't have happened in the first place. I will say it was cheaper than pulling the head & repairing it on the bench.