A couple weeks ago i bought my '98 1500 with a V6 Magnum in it. When i bought it it would not run so my dad and i brought it home on a trailer (which was interesting in itself because he as a Dakota) and put a new fuel pump in it. Now it runs like a champ, but still feels alittle weak. It drives really smooth though which is a plus. When i get up to speed and give it some gas it makes a rattling noise that kinda scares me. it sounds like its right under the truck...any thoughts? I think i can get it running a bit stronger with a good tune up, so if anyone has some suggestions to what i should do that would be great!

 

welcome to the site.. I would guess that the rattle is a loose honey comb in the converter.

 

Wouldn't that rattle when i push the gas and i'm not moving too? because it only happens when i'm in gear and moving.

 

I had a 96 blazer with a 4.3l in it and the honey comb was loose and that stupid thing would rattle as soon as I started it up. When I hit the gas it just got worse. Im not for certian but its a start. You unbolt it from the manifolds and rest of piping and take it down and shake it to see. Or start it up and take a long screw driver and put it on the converter and put the handle tip to your ear should be able to hear it. Also im not sure if yours has a heat sheild on the converter but check that if its loose, if you have one

 

Smack the converter with a rubber mallet, and see if it rattles.....

Also, check and make sure none of your exhaust system is making contact with anything that it shouldn't.

 

its the cat...i got same thing going on....

 

Thanks guys, i'l try that in the morning and get back to ya.

 

might be the cat. might be spark knock from leaking plenum.

if higher octane gas fixes the problem, its spark knock....