[JLH911]

Friend has a 98 5.7 chevy tahoe?. He's getting a code indicating that the number two cylinder is mis-firing. What could cause this? The spark plugs look pretty even and he replaced all the obvious components like wires, plugs etc.

Thanks

[Ryan Graham]

Have you replaced the cap and rotor. The cap can crossfire into the adjacent cylinders if it is cracked. I've seen brand new caps do this. It is also possible for the bottom of the rotor to be burned out and arcing to the distributor shaft. The CPI injector in the 5.7 is not the best design and can become plugged if you are using cheap gas. You can try an injector cleaning on it, but results are usually mixed. There is an updated design injector available that moves the injector closer to the cylinder (easiest way to explain it) and is a much better design. It is also possible (but rare) for the intake gasket to be sunk into the valley, causing full vacuum on the crankcase. To check, pull breather tube (from valve cover to air intake tube) and pcv valve (other valve cover) and put a finger in both at the same time. If you feel vacuum then you have a bad intake gasket. Have you checked compression?