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cam shaft change


Towerlead1
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1990 Nissan Pathfinder 155k miles

 

I broke the cam shaft on the passenger side. 12 valve so no collision. got cam from junk yard install set timing. vehicle idols rough but runs however when you accelerate heavy or hit a hill it bogs and sounds hollow. Ive changed cap and button double checked timing put new plugs checked fire disconnected exhaust. before the cam broke vehicle ran fine. with broken cam the vehicle would still run and drive even down interstate I though I blew a head gasket and dropped one cylinder until to my surprise while taking apart found the broken cam.

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I broke a cam (just behind the pulley) on my 88 once while driving 60mph and instead of just trying my luck I took the head to a local machine shop to have checked out. Wish I could remember exactly what but they found a few things that needed attention as a result (it's documented here somewhere.) in addition to planning the head(*s) they also found *slightly* damaged valves. Once they were done, I put it all back together and it fired up and ran normally.

 

I guess my point here is, don't just assume that everything is okay, just a little damage invisible to the eye could be the issue. Check the timing again and be 100% SURE that it is correct in EVERY aspect. Then if it seems to be right, it might be time to pull the head... or heads... and have them checked by an engine machine shop. Maybe one of the valves is bent just a little and is not fully seating.

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Oddly enough, I've seen VG33 break belts and not bend valves on more than one occasion. But the 3.0 I know you can't get away from that.

 

I bet that is OP's problem. Slightly bent valves.

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