Sudden 30% MPG loss in 84Z

[tripod12133]

I got an 84 Z28, and about 2 years ago, suddenly, the gas mileage went from 23 highway 17 city (with an MSD system that boosted it a crap ton), to 14 highway, 11.75 city. It feels like it has plenty of power so I am honestly clueless.

I just timed it and got it dead on where it should be
It has also had it's plugs and wires changed twice since then
I got new custom wheels but I measured the diameter and it's the same as the factory wheels I had on
I've looked for puddles of fuel & found none & also don't smell any so idk if there's a fuel leak or not

It was very sudden. I drove it down to Tennessee, and got great MPG, then a few days before i came back, noticed how bad it was and it's been that way ever since.

Do any of you guys have any other ideas? I've tried to use my best knowledge of what it could be because its not very complicated, I just cannot think of anything else.

Posted here is a vid of it running, so if you can, listen to it and idk maybe see if something sounds wrong in it. The part where it is idling is at the very end. Please listen to that too b/c I am not sure if it is idling correctly. Thanks so much.

http://www.youtube.com/watch?v=qaYgvzBE7FM


Thanks guys,

Mark.

[wrightz28]

Is it carbed or Crossfire Injected? At work, sorry can't run the youtube.

Either way, I'd start with the O2, it's cheap.

[tripod12133]

Originally Posted by wrightz28

Is it carbed or Crossfire Injected? At work, sorry can't run the youtube.

Either way, I'd start with the O2, it's cheap.

Its a Quadrajet, 4 BBL

[wrightz28]

But still the bare bones ECU controlled correct?