Pontiac Problems? Ask a Mechanic for Answers ASAP
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Terry,In order for the engine to start and run you need good spark at the spark plugs, injector pulse at the injector, proper fuel pressure and good compression. If you are sure you have good spark as well as proper fuel pressure then the next steps would be to check the injector pulse and compression. Post back with the results and we can work from there.
Terry , I suspect the same thing due to the backfiring. The best way to check this is to remove the spark plugs and run a compression test on the engine. If the timing has jumped you will see low to no compression on most cylinders.
The 30 lbs is a very good indication . I would have a look at the valve timing .
Its likely that you going to find some of them low as well. This engine has a timing chain and a nylon gear. I suspect with the amount of miles you have on it your timing chain has jumped.
The 3.4 is not considered an interference engine.
What is your compression reading now?
The second sensor is on the side of the block but it will not effect your compression. See it in the link below.https://dl.dropboxusercontent.com/u/104923897/Crank%20sensor%20Jan%209.pdf
That is likely and the cylinder that has the low compression is like where the problem lies.