engine wabble

[nello]

I know pretty much everyone here has delt with a crappy idle at some point in their SyTy's life, but has anybody noticed or had the problem I'm having?

First off, knocking on wood, my truck starts up and runs great everywhere I take it. I have done several datamaster runs on it and everything looks good from what I can tell, no red codes are visable. I use premium fuel always, replaced all ignition components, and their doesn't seem to be anything out of the ordinary with the truck other than...sort of an engine vibration of sorts. Between idle and 2k rpms i feel a vibration or wabble which gets more intense or shakier at 2k...hard to describe. Shake is visible under the hood in park when revving from the TB. Once past 2k rpms it smooths out and I can't notice the vibration or wabble anymore.

I have searched common motor mount problems but am not expierencing what others have such as rubbing of parts on hoses, cowls, molding, ect...

I have an idea what it could be but I'm really hoping for the best here.

Another thing, if my DM runs are looking good what would be some good reasons my truck is so slow?

One more thing, what's the life expectancy on our Catylitic converters, my truck is at 60k miles.

Please help if you can, thanks.

 

[MikeRenz]

Re: engine wabble

if you look at your motor mounts from under the truck you can see if they are rotted through. Check the drivers side one first, it seems to love to deteriorate.

 

[Don W.]

Re: engine wabble

IMHO Mounts won't have much effect revving in neutral. Hmm, pull the plugs and look for an oddball = low compression = problem. Any noise at all associated with this? Remove the belt and see what happens. Watch the harmonic balancer. TC have a problem causing an out balance situation? Or some other issue in trans, together making truck slow? Just thinkin' out loud...

 

[nello]

Re: engine wabble

IMHO Mounts won't have much effect revving in neutral. Hmm, pull the plugs and look for an oddball = low compression = problem. Any noise at all associated with this? Remove the belt and see what happens. Watch the harmonic balancer. TC have a problem causing an out balance situation? Or some other issue in trans, together making truck slow? Just thinkin' out loud...

Don, compression is good. No odd noises, I'll check the harmonic balancer and mounts too.

About the slowness, how bout the cat? How can I check if it's clogged and need a new one? Anybody? My truck on the DM dyno is saying like 124 hp....weak. 0-60 in about 10sec. I laugh cause I know a lot of peeps are doing 1/4 mile in that time. :rotf:
Something has got to be up with my Turbo and WG. Tranny still shifts hard!

 

[SY2455]

Re: engine wabble

The last time I had what you listed. I found out the Flexplate had started to get stess cracks on another 4.3 that I an installing in my daughter truck.

About the slowness, how bout the cat? How can I check if it's clogged and need a new one? Anybody? Tranny still shifts hard!

1 way you can check the cat is with a press gage with a small hole before and after the cat. another way is to go on a normal drive at night of about 5 miles or so ( not getting on it at all ) The key is normal. When you get back home leave the engine running and opened the hood and look at your downpipe. If it is glowing red you may look at the cat. My cat had broken up and 1 large piece was acting like a flapper and blocking off most of the tailpipe.