I bought an 01 XJ with a Golen 4.6 stroker with less then 15k miles on it a few months ago. When I bought it, it had a miss 1 & 6, took it to the dealership to get it inspected, and was told it was due to a crack in the intake manifold. The guy I bought it from had a ton of other jeeps and was diagnosed with terminal brain cancer and needed the money. he kept pretty meticulous service records and gave me a binder with everything he'd done to the jeep. I put on a new manifold and the jeep ran fine, not great for a bit then started missing pretty bad. Only really missed on decceleration, cylinders 1& 6. Threw some parts at it with no luck and I took it back to the dealership, they said it was leaking from the manifold gasket pretty bad, tightened it all up, still leaking. They also said that some part of my exhaust after the header had dissinegrated causing the o2 sensor to read wrong and run rich. They ran a compression test, great results, 175 psi in all cylinders but #5 which had 180. They did a leak down test which showed cylinder 1: 20% leakdown, 2: 18%, 3: 22% 4: 20%, 5: 14% 6: 30%. They also said all leakdown was from the crankcase and they were pretty convinced it was from piston ring issues. I was pretty suspsiscous as Golen is such a trusted performance shop for the engine to fail and have such excessive blowby at only 15k miles, especially with meticulous maintenance. I theorized it was a valve timing issue possibly caused by the cam synchronizer and the tech responded: "its pretty unlikely with that style of motor because at top dead center(for the leak down test) all of the valves closed as they should on each cylinder. You have excellent compression but on the "bang" stroke, the blowby is excessive to say the least. It is also very very unlikely but if the piston rings were all lined up it would also cause excessive blowby. Again, very unlikely on 5 0f 6 cylinders." Should I seek a second opinion before doing another rebuild? Anything I can do to confirm it needs a rebuild? I contacted Golen earlier today but was unable to get through, I left a message as well as email and am waiting on there response, hopefully I can ship it out to them and they will rebuild it.

 

I'd speak with Chad at Golen Engines if it were me.

 

I'm not an engine guy, but doesn't having 175+ psi on each cylinder clearly show the engine isn't blown?

I'm less familiar with how to interpret the leak-down results.

x2 on getting ahold of Chad. He'll steer you in the right direction. I highly doubt the answer is a rebuild.

 

Third vote for Chad at Golen