6 January 2001 Air Repair
This timely article was written by Scott
Kendall. We have talked about the Oldsmobile
Y engine family in Air Repair before. The
IEPA is also sponsoring a series of seminars
by Braun’s R&D on this subject. Scott tells us
what it takes to repair these vehicles, the cost
factor and dealing with the customer’s
perception of having to invest hundreds of
dollars in an older vehicle. Thanks Scott for
the great story.
Recently I had an experience with
two Oldsmobile 307 V8 VIN code
Y equipped cars. The 307 Y motor
has a carburetor and the reputation
as being one of the toughest engines
to clean up. As I see it, the biggest
problem with a 307 Y equipped car
is convincing the owners to spend
hundreds of dollars on cars that are
over ten years old and in most
cases, beaters. The two cars, one
an 85 Cutlass Supreme with over
100,000 tough miles on it, the other
an 88 Custom Cruiser with 81,000
miles, were laid on me the same
day. It was early in one of the
busiest weeks we ever had at our
shop.
The owner of the 85 Cutlass
was a hard working landscaper and
the Cutlass was his family’s only
car. It failed the IM240 with an HC
of 3.53 versus a composite of 2.00
and a CO of 43.6 versus a compos-ite
of 30.0. He authorized our
diagnosis fee and didn’t seem to
flinch when I told him to be pre-pared
to spend hundreds or he
shouldn’t waste either of our times.
The owner of the Custom Cruiser, a
retired man in his 70s, had just
bought the car. It failed with an HC
of 3.64 versus a composite of 2.00
and a CO of 92.3 versus a compos-ite
of 30.0, a gross polluter. When
the Custom Cruiser started, it was
obvious that it had exhaust leaks
from the engine area. I mentioned
307 Y Motor Fixes Challenging, Expensive
this to the man who owned it and
with a bewildered look on his face
he said he just had the complete
exhaust system replaced. He also
authorized our test fee.
I looked at the Custom Cruiser
first and what I found wasn’t
pretty. The check engine light didn’t
illuminate with the key on engine
off, so of course there was no
communication from the ECM. The
purge valve was bad. The choke
didn’t open all the way. When the
car started, the smell of burning oil
filled the air. As for the exhaust
system, everything behind the
converter was new, but the donut
gaskets at the manifolds were
leaking. The bolts that attached the
flanges to the manifolds were like
my patience that day—thin and
ready to snap.
The owner of the Custom
Cruiser stopped in to check on our
progress so I broke the bad news to
him. The lack of a check engine
light could be anything from a
burned out bulb to a bad ECM. The
carburetor still had its factory plugs
in it, and because of the CO prob-lem
would have to be overhauled. I
had disconnected the extension pipe
from the back of the converter to
take a peek inside, and while the
substrate was still intact, it was
coated with oil. With the leaking
donut gaskets, the potential was
there for the Cat and the 02 sensor
to be too cold to work efficiently, so
if the gaskets had to be replaced it
would be a time and material job. In
short, this car could eat up the
better part of a thousand dollars!
There was no discernible
expression on his face and he didn’t
say a word. Thinking he might be
hard of hearing, I moved closer to
repeat myself; after all he didn’t
hear the exhaust noise. As I got
closer, I noticed the color had
drained from his face. It was then
that he cleared throat and said “do
whatever you have to do.”
I started by pulling up the
Custom Cruiser’s Computer Engine
Control wiring diagram. Grounding
pin G at the ECM had no effect on
the Check Engine Light. The next
step would be to ground pin E of
the Light Driver Module, but it was
a lot easier to remove the dash
bezel and find that someone had
removed the Check Engine Light
bulb and socket. With new ones
installed, I hooked up my scanner
and started the engine. The light
was on and a code 21 TPS voltage
too high was set. The scanner
showed the TPS voltage at idle to
be 2.4 volts. With the engine still
idling, I pulled the PCV valve from
the valve cover. There was very
little vacuum, so I popped the other
end off at the base of the carb and
found it was low there as well. I got
the same result at the choke
housing when I disconnected the
heat tube. The primary choke pull-off
was also bad, which could allow
the secondary air valve to open
early. I tested the O2 sensor for
response to propane and to vacuum
leaks; it was slow and even after
completely warming up the system
would go in and out of closed loop.
My hope at this point was that the
oil burning that had clogged the
PCV and choke passages and
coated the inside of the converter
was also coating the 02 sensor
causing the open loop problem. I, of
course, hoped it wasn’t a cold 02
because of the nearby exhaust leak.
Continued on page 7.
