4.3 Vortec runs rough under load

[slravene]

I need some help with my 4.3 V6 Vortec in my buggy. This motor was not swapped by me, wasnt pulled by me. Its in a tube buggy, not a chevy vehicle, so I dont have much to go on other than what I can find on here.

I had a vacuum leak that I plugged. You can see where that was in the picture. I think this went to the brake booster on a stock truck? Either way...before this was plugged, it would have a rough, surging idle and was tough to keep running. I plugged it and its fine at idle and not under any load (in park) It also revs perfectly when in park. When I put it in drive it will still idle fine and move the buggy fine, AT IDLE and SLIGHTLY above. Any load, speed, uphills, rocks, anything will make it bog down, sputter, backfire slightly, and just run like crap in general. It cant keep 25mph.

I am at a loss...I have no idea about these motors (the only ones I've ever worked on have been propane powered 22re toyota 4cyls) and need to find out why it runs beautifully at idle and not under load, but wont run to save its life once you actually put some power to it.

Could this be another vacuum leak? One related to the vacuum port i found before? What should I start with?

Please help!!

Picture to show where the port was: The intake has been pulled off so you can better see...

 

[slravene]

bump, anyone?

 

[loganstoy]

maybe map sensor,vacume lines and could be dist cap,is it delco or autozone...does it sound like a miss.

 

[3DCrawler]

Really need to check the fuel pressure. Any of the Vortec engines need over 58psi or they get pissed and spit at you

 

[slravene]

sorry, i meant to update this...I got it figured out two nights ago. It was a simple clogged fuel filter. One inline summit filter, two wrenches, and 20 mins, and I am running like a champ.

 

[nickjc]

On chevy engines if they run like shit under moderate to heavy accel and then clear up when you let off, it's the filter and I can see you already fingered that one out so congrats. On chevy stuff with electric fuel pumps like your buggy, don't run it all the time at or near empty cause you'll kill the pump quick fast and in a hurry.