The Italian tune-up - at least in a
diesel [although it applies to a gas car too - Ed] consists of taking a SOUND car out and maximally accelerating
from stop or slow speed to some high speed OR driving at near full rpm
with a heavy load (up long hill) for minutes at a time. The idea is to
get maximal air and fuel flowing through the engine to develop near
maximum heat. This will burn and eject residual carbon that has
collected in the engine. Following such a regimen the idle is usually
smoother and the amount of black smoke at full throttle should be
reduced. This occasionally does not happen the 1st time and the idle
might get rougher or a pronounced knock could occur. This is usually
because some carbon has been "rearranged" but the prechamber environment
isn't appropriate for smooth combustion. Further TREATMENT will clear
this up as more carbon is burned up, but it is a little scary the 1st
time it happens to YOU and your car!
A few full throttle accelerations a week will usually keep most CLEAN
engines cleaned out pretty well. More prolonged "treatment" is usually
required for a car that has had a LOT of city driving. Just a long
highway trip (50+ miles) with several two-three minute full throttle
periods (long 6-8% grades are GREAT) will clean out an awful lot of
carbon and crud that's build up, but with a really "city bound car" it
may may take more than just a few sessions to really get it all out. My
weekly 250 mile trips from Pittsburgh to Washington DC and back over the
last 7 years have given me a chance to really examine the "Italian
tune-up" and the concept of "flailing the heck out of the MB diesel
engine" or at least running it at near full throttle/top speed for a
long period of time.
I referred to a "SOUND" car. To me that means a car that NO serious
mechanical problems. The chain stretch should be below 5 degrees or so,
the valves should be properly adjusted, the air and fuel filters should
be verifiably clean, and there should be clean and it would probably be
best if the injection pump timing is known to be pretty close to correct
(within a couple of degrees). The cars/engines I presently own, have
THRIVED on this regimen. Idle smooths out, smoking diminishes, and fuel
and oil consumption goes down. I can't promise that on an engine that's
worn out, but nobody else can either ;-)
Marshall Booth
