Random miss on cylinder 3.

[GDIMammothTank]

Just bought my King Ranch Expy and it has a miss on cylinder 3 the day after I got it home from the dealer. It has 192,*** miles. They claim that in the time the dealer owned the vehicle, they did all 8 plugs, the fuel injector on 3 and a coil pack on 3. The tech is requesting to pull the valve cover and visually inspect the "drivetrain". Does my dealer's tech really know what he is looking for or are they following the wrong path. Tech said he did a cylinder test and a compression test on 3 both it passed with flying colors. They are hoping to find a sticky valve. Not sure if anyone else has had this problem or something similar.

 

[JamaicaJoe]

The valve train is what they are talking about. The 3 valve/cylinder engines have weak cam followers/rocker arms. The needle bearings give out and then the entire $5 part pops out and if you are very very lucky that is all that needs correction. But, many times the camshaft lobe gets scored and sometimes the valve spring retainer pops off and then a valve drops into a piston. Hoping you are under some sort of dealer warranty. Since they already did the usual an injector and COP on #3 before you bought the car, it sounds like an existing problem they hoped would "go away" as you drove off. You might want to prod them into replacing all those buggers and camshaft, even if you have to shovel some cash their way. Then of course, there is the other camshaft , the timing chain etc, at 198K miles......

 

[Trainmaster]

Yep, the valve train should be checked out at this point. Pulling the valve cover will give that opportunity. Hopefully it's just a single rocker arm. But as Jamaica says, not a bad idea to check them all out, replace some things and possibly replace all that timing stuff that's the weak link on these motors.

 

[GDIMammothTank]

They ended up fixing it all on their dime since it was pre-existing and didn't disclose it when I asked if there was any reason why it was in reconditioning for so long. Wife was mad we're keeping it but it is in great shape besides that issue. I'll attach RO to show all they did on their own dime.