I started having trouble with my blazer backfiring and missing. I took it to the local shop and they said its got a p1345 code showing and the cam retard is 93 degrees off. i took it home and lined up the timing marks on the balancer and checked the rotor to see if it lined up to the tab with with the 6 on it. It didnt line up. Does this mean the timing chain has jumped a tooth? Any help would be appreciated. Thanks

 

Did this happen all of a sudden on its own? Has the distributor been recently removed? Has the engine had work done to it recently?

 

It happened all of a sudden while driving. No work has been done exept for changing sensors. I pulled the dizzy after checking the timing marks to see if the gear was worn and it wasnt. I went through proper procedure to reinstall dizzy and it wont start at all now.

 

What year is the vehicle? How many miles are on the engine?

First thing to check is timing chain slack. It is not common for the timing chain to jump on this engine, but it's worth checking given what you've found so far. Remove the distributor cap and move it out of the way so you can see the rotor clearly. Using a socket and ratchet on the vibration dampener bolt, slowly rotate the crankshaft clockwise, (do not rotate counter clockwise) until the marks are aligned like this:


Have an assistant closely watch the rotor while you slowly rotate the crankshaft counterclockwise. When the rotor just begins to move, stop rotating the crankshaft. Measure, in degrees, how far the crankshaft moved. Post your results.

 

Its a 2001 with 200000 plus miles. The crank moved approxmently 3/4 of on inch before the rotor moved. I guess about 10 degrees.

 

That's not enough to allow the chain to jump. Once it gets up around 12 or 15 degrees it's time to think about replacing the chain & gears. I've got a couple of these 4.3's that I service, with almost 400K on the original chain & gears, they each have about 10 degrees slack.

OK, next step, perfectly align the marks like you just did, (clockwise only) but this time make sure the rotor is pointing within a few degrees of the "6" on the distributor housing:


If the rotor is not within 4 or 5 degrees, pull the distributor and install it so it is.

Edit: The arrow in the image points toward the front of the vehicle.

 

i did that when i got it back from the shop. The rotor did not line up with the mark. it was around 90 degrees off. I removed the dizzy checked for wear and installed with all marks lining up and it wont run at all now.

 

Does it backfire while cranking: either through the intake or out the exhaust?

 

it will run It just sounds like it is running on 1 cylinder.

 

no backfire though