1986 Suburban will not stop running HELP

Jim says: Mine (85 Sub with 454 and Calif. emissions system) does that
too. And the exhaust smells really acrid after one of those run-on
episodes. I assume the run-on is due to 87 octane California
reformulated regular gas I use, in combination with deposits in the
combustion chamber. But I haven't tried a tank full of 89 or premium
gas, nor have I tried using a fuel additive to clean the chambers.
Maybe someone on this ng will tell both of us what to do! Hopefully no
snide remarks like "add it to your local artificial reef." Jim

Also the idle speed may be a bit high, which combined with all other factors can
aggravate a run-on condition. I would try the fuel additive as well as higher
octane gas for a while to see if it will help. Anyone who would say to add it to
your local artificial reef is nuts, as an 85 Suburban owner, there is nothing like
them except another one (preferably new).
Roy

Run-on (AKA dieseling) results from carbon build up combined with low octane gas. The
carbon creates hot spots which in turn cause pre-ignition.

If you regularly drive it at high RPM and high load, then you might safely try the
following:

Make 2 or 3 runs up a hill at full throttle--if you blow a lot of smoke on the first
run, and then it clears up, then you've blown out some carbon. I used to do this on
my 350 chevy--not because of dieseling--just whenever it started running little rough.

If you regulary drive it like a baby, then don't try this. An engine which has nver
seen high RPM and load will (according to the folklore), wear the ridge a little
lower. After 100,00 miles, if you suddenly get on it, the rods stretch just enough to
send the piston enough higher to break a ring.

If nothing else, try higher octane gas. A lot of older cars with high miles will not
run on 87.

For a ten year old car, it may be time for a valve job / carbon cleanout.

My 86 says to use 89 or higher octane even when it was brand new. The engine
has been rebuilt ( bored .060 over ) so I use super ( usually 92 ) all the
time.

CURRENT:
1979 23.5ft. Shasta Travel Trailer
1985 Chevrolet V8 S-10
1986 Toyota 4runner
1986 GMC 3/4T Suburban
1993 Honda Civic

PREVIOUS:
1972 24ft. Continental Travel Trailer
1980 CJ 7
1982 Mercury Zepher
1982 Chevy Camaro
1985 Toyota p/u

Thanks for the input on my Suburban. I did find a bad primary choke pull off
vacuum switch. I tried pulling this in with a rubber band. Car would not start
at all so I took it off. Got a new pulloff switch today. We will see if that
helps.

In article <19981120023208.02126.00000@ng-fu1.aol.com says...

Changed the choke pull off today. Starts great, idles nicely when cold. This is
the second time I have had to change the pull off vacuum switch. If you are
having trouble with cold running this may be your problem. Also put in a
stainless steel thermostat. I did and it is the first time the temperature has
stayed stable since I bought the truck. About 80,000 miles ago. The other
thermostats looked good when I removed them but were not operating properly.

In article <>, says...