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Dave Nova
Dave Nova, Pontiac Technician
Category: Pontiac
Satisfied Customers: 19452
Experience:  ASE Master Certification. GM World Class Certification
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I have a 2004 Pontiac sunfire, the timing chain tensioner went

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I have a 2004 Pontiac sunfire, the timing chain tensioner went bad and bent all valves on exhaust side. The mechanic replaced: Timing Set and tensioner, Head (reman with new valves and seals, springs were ok), all gaskets and head bolts. Car was put back together. The car cranked up and ran for approximately 10 mins. There was a metallic pop and the engine shut down and will not crank back. Now no cylinders have compression. When engine is rotated cams and valves operate smoothly, mechanic checked cam timing and said it was good. No strange noises when the engine is turned over by hand or with the starter it just does not have any compression and will not start. Do you have any ideas as to how it can go from running with good compression to not running with no compression? I was there when the engine just quit running. There was only one metallic noise. Nothing appeared to be broken. What would cause this. The machine work was done by a reputable shop.

The camshaft could have broken. Remove the valve cover and turn the engine over to see if the rocker arms are moving.

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Customer: replied 7 years ago.
I have already checked the cams for breakage. All of the rocker arms actuate like they should. Is there any kind of decompression valve on this engine? Do you have any more Ideas as to why this happened
No decompression valve on this engine. Since the cam is turning, there are only two possible causes, Either the timing chain jumped time, or you have some bent valves. Recheck the timing chain alignment. If it is correct, the head will need to come off to check the valves.