5.2L Shake Shake Shake

I have a 1984 5th Ave with the 5.2L(318) engine. It will start ok when
cold, but after I drive it for a bit, Let it sit for, oh, about a half
hour, then start it again, the engine shakes so much that it feels like
my teeth are going to come loose. Once it's going, it drives ok, that
is until I come to a stop. Then it starts shaking all over again. I
mean BAD. Almost (and sometimes does) stall. Does anyone have an idea
as to what may be causing this? Thanks.

Tubbsy

 

sounds like it might be idleing to low when the engine gets warmed up.
a tuneup should fix this easy enough. and if its carb driven even
easier.. there should be a screw on the side of the carb, just turn
it.

 

The only thing that stumps me is that it idles fine even after it is
warmed up. I can drive 20 miles and the engine is fine, even in stop &
go traffic. It's only after it sits for a short period of time (after
it starts to cool down, but before it's cold) that I have the problem.
Personally, I think it's a carb problem, but I don't know what to
adjust. It's not anywhere as simple as my 1967 Dodge Coronet (which had
a 318) was to work on WAY back in 1982. TOO much smog crap on this car.
And Lean Burn? I don't even know where to start. Thanks.

Tubbsy

 

The pickup coil/ring in the distributor? Vacuum leak?

Bob AZ

 

Another thing that sometimes happens on carburetors (remember those??
this car's got one!) is that one idle circuit will cease working
entirely due to being dirty, damaged, or improperly adjusted. When that
happens, the car only idles on 4 cylinders (if a v8 and using a
dual-plane intake like a stock 318/5.2 does). Feels a little like
sitting inside a paint shaker. Try backing the idle adjustment screws on
the front of the carb ALL the way out (removing them) and blasting
carburetor cleaner into the holes where they went. Clean the screws with
carburetor cleaner and a soft cloth (don't lose the little springs that
go with the screws!) and then reinstall them and adjust the idle mixture.

If you don't have a service manual that gives the procedure for setting
the idle, bottom the screws out (GENTLY!) and then back off 2 turns
start the car and warm it up, then adjust for the smoothest/fastest idle
or (better yet) highest manifold vacuum reading. You'll have to adjust
both screws, then adjust the idle speed back to spec, then re-adjust
both screws again for several iterations.

 

Well, I played around with the vacuum lines yesterday, and come to find
out, there was one plugged into the wrong place (I assume) in the
passenger's side firewall. I have NO idea what the thing does, but the
connections look like identical twins with inlets (outlets?) on the
top, bottom and side of whatever the heck the connections are for (do I
sound like a heart Dr?). As soon as I unplugged one hose from the
firewall connection, the car started idling perfect. I'm stumped as to
what the connections are suposed to do. All I know now is that I have a
vacuum line connected to nothing, a twin "unit" on the firewall pretty
much connected to nothing (now), but the car idles much, MUCH better.
If I haven't said it before, I HATE emission controls!!!!!!!!

Tubbsy

 

Most likely the EGR control valve (your description wasn't that bad
The EGR servo is located on the maifold by the carb- watch/feel for its
stem to move when you plug that line in. If it does, then you've found
the issue. That control valve should enable EGR when the engine is warm,
but it shouldn't engage it at idle.

Don't know if you'll pass an emissions test with the EGR deactivated the
way it is now, but if you don't have to have a test in your area, you're
OK. Be observant to see if it pings any worse than it did before- EGR
actually helps suppress detonation, but the feedback carb engine control
systems on the M-body didn't really depend on EGR the way some EFI cars
of that era (notably the Cadillac 4100) did to prevent self-destruction.

 

motor mount?