Roger Mabry

I have a new project, '93 LT1/700R installed in a '72 Jaguar XJ. It runs, but poorly. Cylinders 6 & 8 have sooty black plugs, not oil. The plugs and spark plug wires are new and test out OK.

Headers on the car make it almost impossible to check compression. Any ideas of where to start?

GM manual is on the way but I am looking for ideas in advance. Have no check engine light yet, so pulling any codes has to come later.

Injuneer

Running rich on one bank of the engine is usually the result of misfires on that bank, exhaust leaks before the O2 sensor on that bank, or faulty O2 sensor or wiring.

Wild1

Agreed. You may have a header / manifold leak. Do you hear any noise "popping" like a header gasket?

Try a seafoam clean and see where the leaks are.

Roger Mabry

There is a header leaker at the top of the collector on the driver side. Bad welds and the PO had them recoated with the leak!

Can the leak on the opposite side cause this problem?

bubba4

I just cured a very similar problem with my 95 Z28. After new opti, wires, plugs, and resealed intake, My code scanner still showed the right bank go rich after close loop. I pulled headers and sure enough the gaskets were bad. I applied ultra copper to the new gaskets and cured my problem.

Roger Mabry

The drivers side headers will come off today for rewelding and recoating. I also found the near new Powermaster alternator is not putting out any voltage. After charging the Optima overnight, the car ran and started better.

Hopefully the GM manual will come this week and I can get actually started.