Finally figured out how to get back into my account. So I have a 1997 Chevy Tahoe 5.7 vortec. It has p1345 code as well as low compression in cylinders 1,3,5, and 7. Have replaced crankshaft sensor, camshaft sensor, distributor, as well as took it to a shop to have it timed. Each mechanic shop I take it to has different suggestions and nothing this far has fixed this tahoe. Last mechanic suggested failing piston rings( don't want to tear into it unless I'm 100% sure that's the problem). It has a small amount of black smoke from exhaust, runs rough and is a hard start on cold days. Sparks plugs all look the same(normal) Any suggestions? I'm about at my whits end with this one.

 

You need to do a dry AND wet compression test on all cylinders on your Chevy.

In addition, here are more possible issues:

• Faulty camshaft position sensor (CMP) (P0340 code)
• Faulty crankshaft position sensor (CPS) (P0355 code)
• Stretched timing chain
• Incorrect distributor positioning or bad distributor
• Bad wire hardness connection (can get burned or become frayed)

 

did the timing check fix the dtc
What were the compression test results?

 

Timing it didn't fix the tdc. 40% low compression on cylinders 1,3,5 and 7. Have already replaced crankshaft sensor, camshaft sensor, distributor. Used a stethoscope to listen for timing chain but didn't hear any looseness. Wiring harness looks good as well. Could the camshaft/crankshaft code cause low compression in all cylinders on the driver's side? Or do I have 2 issues at once?

 

the actual compression readings in psi for both banks would be helpful.. not enough testing done to confirm much

the next step would be wet compression test, cylinder leakage test...and if inconclusive...on the one bank with low compression, pull the valve covers and inspect the valve train,
any signs of a blown head gasket...combustion gases inthe coolant can be tested and you could see bubbles in teh coolant if a cylinder leakage test was performed.