MPG has Plummeted !!! Lost 10 MPG. Help !!! Coil / timing issue ????

07-29-2011, 09:33 AM
1984 Z28, 305 non-hypo.

Thats a thought I have.

I put an MSD ignition system on it. Before it was 16. After it went up to 23. BIG jump.

But for the past couple years, the gas mileage just plummeted even lower than before down to 14 mpg !!

Any ideas??

Could a bad MSD box do that ??

K heres what Ive been thinking.

I cant smell gas, so probably no gas leak.
There doesnt seem to be a loss of power, so likely theres no muffler or cat clogged up.
Its full of tranny fluid.
It has been tuned up and timed, and been given new plugs and wires
But one weird thing ... when I put the key into the computer to read the codes ... it doesnt flash them. Like thats messed up or something

So honestly I dont know. Ive racked my brains many times and I cant figure it out. MAYBE there is a loss of power and I just dont notice it.

Another thing, what if it has jumped time ???? How can I tell if it has ?? It runs but has some weird sputter when its running. this MAY be it.. but idk how to test it. any help please.

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