hi. <BR>Our malibu which has a 350 is being quite bizarre. One day as we were out riding, the engine revved WAY down, then back up, then back down again, and back up until it just killed. after this it would just continue when you got up to speed. I changed out the fuel filter, which was pretty dirty. after this, it seemed to work pretty good until you were up to full throtle. So we just packed it up on the trailer and headed back, I figured there was a little crap left over in the lines and all would be good.. well today we went back out and the same problem from the beginning is occuring.. as soon and you go faster than idle, it goes back to revving way down then back to your throtle speed... im wondering if this is possibly a fuel pump?? im not sure.. could it be electrical.. I know a lot of you guys are brilliant with this motor, please help a fellow out <img src="http://www.wakeworld.com/MB/Discus/clipart/uhoh.gif" border=0> thanks a lot!

is it carburated? if it is sounds like the accelerator pump

yes it is carburated. accelerator pump you say?

or idle passages. One thing you can do is take the air cleaner off and look into the carburator with the engine off and someone pumping the throttle there should be a steady shot of fuel going in. If not then you need to change the accelerator pump. very easy to do. The other thing is that the idle passages may have gotten cloged so you can remove the mixture screws and bloww air through them. just remember how many turns you turned them out

buuutt... the think is that it doesnt hesitate until the trotle is open

On my Cobalt with a 302 Ford I had a similar problem at higher throttles, and I messed with the air/fuel mixture adjustment screw on the carburator until it ran like it should. Don't know if that is the problem, but might be a possibility.

yup that is why it is most likely the accelerrator pump. Do that test i told you about

What kind of carburator do you have?

i believe its a Rochester Quadrajet..

Also need to know if you have a mechanical or electric fuel pump? Mechanical fuel pump check valves can sometimes go bad along with the diaphragm itself. <BR>But if you have the ability to take the top off of the carb, then check your needle and seats for debris, and check your floats to see if they have a hole in them.

darn its a quadrajunk, man now all bets are off, it could be anything.