ok guys hopfully someone has some info on this problem. i have an 07 1500 with the 5.7 hemi, about 42k miles on it. k&N CAI, flowmaster 40, diablo predetor.

at low/medium throttle the engine seems to vary slightly in rpms making an odd sound. i dont actualy notice the tach changing but i can hear it. at prob 75% throttle or more it seems fine.

im thinking it needs new plugs and maybe a fuel filter? it has the original plugs (i had a local shop tell me the plugs should be good for 100k)
im also worrying it might be something worse, like torque converter or trans

any thoughts? thanks for any help!

 

Change your plugs and clean your TB. The plugs should be done every 30k if they are the copper one's.

 

ok, im betting they are the copper ones, ive been planning to have them done for a while just haven't had the time or money. should i replace them with the same plugs or do you have a better recommendation?

how do i go about cleaning the throttle body?

 

Most guys go w/ the champion coppers that come OEM, you can also use ngk copper plugs as well. To clean the TB you need to pull it off and spray it w/ brake cleaner and scrub off the gunk, just be careful not to spray the electrical connectors.

 

What you are describing sounds like MDS going on and off to me. Sounds terrible with aftermarket exhaust IMO. Shut MDS off with your Diablo and it will sound much better.

And yes change the plugs and clean the throttle body. OEM coppers are fine.

 

yes the mds does sound terrible with an exhaust!! that was half the reason i bought the diablo lol. that's not the noise i was noticing though, it was alot more subtle than the mds noise.

today i changed from 91 tune to 87 tune, only thing i changed on the tune was to turn the mds off. i didn't notice the noise so im wondering if it was something to do with having the throttle sensitivity adjusted when i had the 91 tune installed (however now im getting some knk so i have to sort that out )

im going to see if i can get the plugs changed in the next week or two, and the TB sooner if i can find the time

 

Mine always does that on the 91 or 93 octane setting when it's cold and I first take off in the morning. Nothing to worry about. It is something in the tune and is probably from the timing being advanced.