I've got a 95 s-10 with a vortec 4.3, love my truck.
It started running rough and sucking up a lot of gas, actually spitting out the tail pipe. I took it into the shop and they said O-2 sensor, and replaced it, at a healthy markup. The fix didn't last long maybe 3 tanks of gas. Took it back and they said the other O2 sensor, so I replaced it, less markup. Again it started spitting gas. I got lots of different advice.
New plugs, checked for leaky vacuum, I split the manifold to see if there was a obvious issue. EGR isn't clogged and operates freely, there isn't any standing gas under the manifold. The only visual thing is the left bank is more oily looking than the right. I could take it back to the shop. Is there anything I should/could check myself before I put the parts back together?

Is this a Vortec motor or a Throttle body injection?

Jeff

Sounds like you need a new fuel injector assembly. They are notorious for leaking under the manifold. That would explain the one clean sideof the manifold.




78 Corvette Pace Car For Sale-18k mi orig-Florida

It is a Vortec, with maybe 35,000 on a replacement injector unit. The origional one leaked into the manifold pretty bad before it was replaced, that's why I thought to look.
I read a posting by strawberry about a flooding Vortec and it does look like fuel is coming out the tail pipe. After pulling a trailer for 20 mi. the front of it is splattered with black and wet.


(This post was edited by Jeff Weisbrod on Oct 7, 2009, 11:23 AM)

You can use a fuel pressure gauge to determine if the pressure is holding when shut off to find out if the injector is leaking or not.




78 Corvette Pace Car For Sale-18k mi orig-Florida

OK, but not to confuse, there isn't gas standing in the manifold this time, but it sure is black especially the left bank.

Black is good. It's the clean part that indicates fuel leak.




78 Corvette Pace Car For Sale-18k mi orig-Florida