2008 Holden Commodore SS comes stock with the Chevy L98 6.0L V8

Question

Hi please I really need your help I have a 2008 Holden Commodore SS comes stock with the Chevy L98 6.0L V8. I was over taking a truck I went from 6th to 4th gear but wasn't quick enough so I threw it into 3rd passed the truck then geared back to 4th, 5th then we heard a faint pop noise and power cut out completely tried key starting it no good also tried clutch starting it while it was still rolling no success I done a system scan I got the codes P0690 P0340 but the P0690 I got only once but a day or 2 later still can't start it but only got the P0340 code not P0690 any help would be extremely appreciated my cars been sitting in a country town motor inn for over a week now the Holden dealership tried telling me that my timing jumped a tooth I spoke to a LS engine expert who's told me there's no way possible that could have happened coz I wouldn't be able to still crank the engine. It cranks but doesn't start and back fires from the air filter intake where the throttle body is I've checked fuel rail all fine checked sparks n leads also fine injectors are good working order also

Answer 1

They are correct you jump timing, when you start the engine , the ignition system  and the injector randomly fire until it catches once it catches, the ECM synchronizes it, it will not catch your  timing is off, the intake valve is still open this is where a intake backfire occurs. , where a what may of happen the timing tension pieces fell apart.  The engine that you have it is very common that carbon deposit develops on the intake valve which causes misfires , rough idle, a no start, no power but the engine will start, and there would no intake backfire.you have a mechanical condition . as for the P0690 you have ignition spark so you can rule out P0690

Comments

My engine hasn't started since the incident how would I go about fixing the problem I'll have to fix it myself I really cannot afford a mechanic right now

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When the engine back fires from the intake this means there is more air to fuel. best route is you need to measure the fuel pressure. You spray carburetor cleaner into the throttle body opening but you also need to be aware you will also set a throttle body code with a high idle that if the truck start,