My 4.3L VIN W is acting up again. It stumbles and surges with the throttle open very much at all. I had this problem a few months ago; at that point, it got a new fuel filter and EGR gasket (I'd replaced that last July, and apparently screwed up the job).

While I was out looking at it just now, I noticed something strange: a kind of pulsating whistle from the engine, near the front, that varied with engine speed. It was worse after revving the engine up a bit, and gradually died down and went away at idle - but it came back when revved up again.

This sounds like an air or exhaust leak. I tried listening through a hose to locate the whistle, but wasn't able to. It's not the A/C or alternator bearings, that much I do know.

It's an OBD-II, but there's no MIL, and I'm pretty sure that there aren't any codes stored (it doesn't seem to do that, for some reason).

Now what?

 

Dunno about the whistle, but it's definitely got a fuel problem. It died and wouldn't restart on the way to my mechanic today. He cane to where it is, had me crank it while shooting brake cleaner into the throttle body, and whaddya know, it'd run as long as he kept squirting. I'm going out of town for a week, and expect it to be fixed when I get back.

 

Well, so far, it's needed a fuel pump and the injector spider. I had him replace the fuel gauge sender while he was there. I'm also thinking about having him replace the fuel pressure regulator while the intake plenum is off.

He said that two injectors were barely squirting anything, and a third was pretty anemic. I'm hoping that fixing that will improve fuel economy, since I won't have to push it as hard to make it go.