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88 mj sputter and backfire no power

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The deal is I have a 88 mj 4.0 auto trans PO beat the piss out of it so far I've replaced one pushrod,timing chain&gears,vacuum lines,etc. Took apart head and replaced a bent pushrod,brand new gaskets on the thing,all vaccuum hoses have been replaced within the last 3 months,all injectors are firing,after installing new pushrod it still acts the same. Also replaced fuel filter&pump.

Currently rebuilding another motor for it out of a 94.

Any ideas?? thanks in advance

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According to my limited mechanical knowledge, en engine backfires when an intake valve is open at the same time the spark plug is firing. I would look at either the valve timing or the ignition timing -- or both. Or, if you changed the plug wires, check the firing order.



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If it's backfiring, it is virtually 100 percent certain that the timing can't be good. Check it again. Be sure #1 is at top dead center ON THE COMPRESSION STROKE, then check the distributor to see if the rotor is pointing at the #1 terminal in the cap.

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