Tech Tips

89 Chev Suburban 7.4 V8 TBI 129k miles

Sometimes I feel nostalgic and I use my old Sun 1011 for some basic testing, its so easy to hookup and there is no warm up time so you can start testing right away. On this suburban that failed emission testing, it's easy to see why with the kv readings on these cylinders. What's interesting is that they are all the cylinders on the left bank and that might give you ideas that lead you down the wrong path, many a time I have seen bad intake gaskets that with give these readings. Big block Fords and Chevs are famous for this. But,

I put the Interrogater on this to see tailpipe readings so I could check HC per cylinder during a balance test and the intake gasket wasn't the problem. It's hard to imagine that every plug wire on the left bank would be open, but that was the case here.

This has to be the result of pulling wires incorrectly, breaking the core of the wires, do a twist and pull on the boot, not the wire.