I have a 2000 GMC Savana conversion van 5.7L 350 V8 that had a fuel pump go out.
The shop I brought it to replace the pump and all was fine, except it was not.

I started to get around 4 miles per gallon and I was really upset they
screwed something up.
I had the wires replaced as it needed it and a full tune-up as long as
it was in the shop. They broke my distributor, so instead of a cap and
rotor, I had to replace it all.

Still getting bad gas mileage, now I have a leak from my water pump
and other things just started to go wrong. I paid them a ton of money
and still, things did not get fixed, so I found a new mechanic to find
out why my van out of nowhere started to have multiple issues.

The new mechanic found out that #2 #4 #7 were misfiring. The van had
sat for many years and was rarely used so it needed a ton of cleaning
and other things done. I looked up why it misfired and had everything
fixed we could that would cause this. New injectors, new plugs, new
wires, full tune-up, everything. Yet it still misfired on #2 #4 & #7.

We figured it out that the computer was bad as it was acting up. We
replaced it and it still misfires on #2. This time the light would
come on but did not before. Service Engine Soon light comes on and the
engine runs roughly #2 does not fire and I burn lots of gas.

He resets it, and the light goes off and runs great. I turn a corner,
run over a bump, start or stop and then restart and the light goes on
and burns gas like crazy. If the light is off, I get about 15-18 MPG
or so. If the light is on, I may get 4 MPG as I used a 1/4 tank to
drive 20 miles. I bring it back to him, he resets the computer. It
says #2 misfiring again.

This is driving me nuts as I am a mechanic myself, but just older
models and this new stuff is driving me into the poor house fixing it
over and over again and it still misfires and burns all my gas. To me,
it has to be a wire somewhere connecting and disconnecting.

Why would the light go off and on just from turning a corner? We have
checked everything from the gas tank to the vacuum lines and replaced
everything we can think of and it still misfires.

I am in Minnesota and cannot afford gas as it is, and cannot afford to
keep fixing all this stuff and still not have it fixed. At this point,
if I have to put any more money into this van I might as well just
sell it as I am getting close to the blue book value in repairs alone
and maybe just need to junk it. Yet I am out almost $10,000.00 so far
and counting.

Please let me know what you think, or if you can help at all. Thank you.

Ronald