93 vortec surges

I just got my 93 blazer with a 4.3 vortec in her and the engine sounds a bit funny to me. In park running she will, from what it sound s like, rev down then up then down and continues this till I put it in gear. Then we rev up then down then up. Is this normal? Oh a complete tune up was just done wires, plugs, egr valve, cap, rotor the works. Thanks guys & gurl

Check and clean EGR valve and passage, but purchase the gasket for it before you remove it. Clean it out and the port it rests on with throttle body cleaner, make sure that there is no carbon fouling up in the valve seat, keeping it partially open. Put it back on with the new gasket and reset the computer by removing the negative battery terminal from the battery for a few minutes. Plug her back together and see if that fixed it. If it hasn't check back here... there may be other issues. However, I must ask - when was that stout machine last given a complete tune-up? Try that, including new air and fuel filters before you yank the EGR off. Mine was freshly tuned and it acted like you described - to find a chunk of gunk just behind the EGR pintle...

This is just to general to help you with.

What kind of sounds?

well it sounds like it reving up, and reving down. Don't qutie know how else to explain it. (pull throttle cable it revs up same sound)

Oh a complete tune up was just done wires, plugs, egr valve, cap, rotor the works. And air filter, gas filter

Check for vacuum leaks first.

Is your engine the Vin W?

why yes it does jave a "W" in the vin does that tell you anything? sorry I am new to all this

Yeah, the VIN "W" machines have issues with the fuel injector and regulator under that plastic black and orange plate on top of the engine that says "Vortec" on it. I still say on a hunch to try that EGR cleaning, but BlazerLT's got a very valid point. A loose vacuum hose or a cracked gasket somewhere can do the same, wild up and down revving of the engine. Checking all of your hoses before taking the EGR off is an easier job, so look into that ASAP.

Is your AC on when it's doing this, could be the AC clutch kicking on and off

ok I am going to be grabbing a chilton manual monday, I will check all the vacume lines. And it does have air but I never use it.

ok through the timing light on it for the heck of it and it shows it 10 degrees advanced. What is the normal advance for the engine plz

did you have the timing wire disconected?

wow what a weird Q. i am sure I read it correctly and know how to use it if thats what you are asking. Would you know what the normal timing is for these engines?>

I am asking you if you disconnected the timing wire from the PCM under the dash. It is a brown and beige wire.

It needs to be disconnected to time the engine properly.

no I didn't thank you for the tip on my way to do it now. Thanks for not taking my mast reply as smug, it wasn't meant to be.

That wire needs to be disconnected to set the base timing.

When you connect the wire, that is the wire that controls the spark advance.