Hello all,

When I coast downhill for any amount of time, then push on the gas, my '97 XK8 emits a smoke screen behind me. I cannot quite discern the color, but I'm thinking it is unburned excess fuel - as some of it gets drawn into the cabin and smells like an extremely rich condition / unburned gas. I would think that if the rings or seals were bad & oil was being drawn into the cylinders from the increased downhill vacuum, that it would smell like burning oil (which it doesn't).

What should I put at the top of my troubleshooting list? Too much fuel pressure due to a blown FPR? Would that force the injectors to leak? I do notice that my long term fuel trims are extremely negative (about -17), so perhaps there is excess fuel leaking into the chambers and the ECU is trying to lean things out in general.

Advice appreciated

 

If there is enough unburned fuel to cause smoke, your cats are probably fouled. Oil smoke is white, a little blue. If your injectors leak, you should have black smoke at startup, and maybe difficulty starting due to bore wash. Get a fuel pressure test kit and see how fast the pressure drops after you shut the engine off.