It's because there shouldn't be a need to connect a frikken computer to a vehicle this old to find the problem. I have a problem with the concept, not the persons.
Hello DeCaff2007,
I was intrigued by your comment about "the need to connect a frikken computer to a vehicle this old to find the problem."
Because I think that are many people out there who share a similar perspective. But since I am actually old enough
to have fixed stone age style on pre-Closed Loop engines (and got away with it) I'd like to explain all this from a slightly
different perspective.
THE PRE CLOSED LOOP UNDER COMPUTER CONTROL ENGINE TROUBLESHOOTING
* Through the '50s, '60s, and '70s the only computers in the car were
mechanical ones.
The camshaft set the firing order and what rpm range that the engine was designed to run in.
And the carburetor determined the Air/Fuel ratios through a variety of overlapping systems.
(main venturi/jetting/air bleeds, accelerator pump, metering rods or power valve, secondaries, choke system.)
And the only real feedback loop was where the vacuum advance on the distributor and the spring-loaded
metering rods in the carburetor would 'monitor' the intake manifold vacuum in real time and infer the
'load' on the engine, and vary the delivery of spark advance & A/F ratios accordingly.
Important: Other than those 2 items, the engine operated in a
OPEN LOOP mode. A good mechanic
could observe the symptoms, make necessary adjustments to the appropriate side of the triad (Spark, Fuel, Compression)
and get the engine back to running correctly. It's important to remember this Open Loop concept,
for as a troubleshooter everything makes sense, and you aren't fighting another entity for control
over what's going on under the hood. (!)
THANKS TO EVER-TIGHTENING EMISSIONS, THE ENGINE BAY EVOLVES INTO CLOSED LOOP COMPUTER CONTROL
So back in the good ol' days, let's say that I'd get the chance to check/adjust
the state of tune in your engine bay once every 12 months, for you were better than the
average car owner when it came to keeping your car in a good state of tune.
But with the mechanical points wearing, the carb float that would take on fuel and change
the level in the fuel bowl, accelerator pump cup wear, the spark plug gaps opening up, and a bunch of
other reasons, as time wore on the tuneup went away, with performance drooping and emissions
skyrocketing. Compared to today, it really was the caveman era of internal combustion.
So why complicate things even more with a computer under the hood? Because even our slower
EFI systems perform the equivalent of my careful adjustments up to 12 times
each second.
This is much faster than the old 'once every 12 month' interval of the human-based closed loop tuneup.
(12 x 60 x 60 x 24 x 365 days = up to a theoretical 378,432,000 times more often via closed
loop computer fine tuning, a noticeable improvement.) And some of the newer-generation
ECU/ECM/PCM/VCM/0411/(etc) slice & dice this stuff even faster. The mind boggles.
Or think about this for a moment. I'd put a sharp tune on my buddy's 350, fed by a
Q-Jet and sparked via a HEI distributor with 'the good rotor' upgrade in Kansas City,
elevation 909'. Runs *mint*, he's stoked.
He proceeds to drive it to Denver, the Mile High City. (Elevation: 5,280') Now running a bit
sluggish, not so good. And then on to Colorado Springs, where it runs even worse.
(Elevation: 6,035') He's on a pay phone near the Garden of the Gods asking WTF? And
I'm the bad guy when I tell him that driving up Pike's Peak is not a good idea? (Elevation: 14,115')
But by the time he's zoomed back to KCMO via I-70, everything looks fine, right down
to the spark plug coloring. That's right, back in the good ol' days, 99+% of the carburetors
out there could not compensate for altitude. Of course it was standard practice if you
moved there that you would re-jet your carbs to match the altitude?
Fast forward to our GMT400 vehicles. They got this little widget called the
Manifold
Absolute
Pressure sensor, and thanks to this none of the above happens. KC to Denver
to Colorado Springs to Pike's Peak, and no issues, your getting a fresh tune up at least
12 times per second, no matter what altitude you find yourself driving. :0)
****
By the same token, there's no free lunch. In exchange for all this tip-top non-stop tuneup,
you have to learn to refer to this as your engine running in 'Closed Loop' (endless tuneup)
mode. Worse, as long as everything is working properly you are living the good life. But if
something goes wrong inside this Closed Loop world, up is down, left is right, something
loose and rattly in the exhaust pricks the ears of the Knock Sensor, which tattetails &
causes the ECU to pull 15 degrees of timing from the spark advance. Meanwhile there's
no SES light or error codes stored, for as far as the computer can tell, everything is working
per design?
...but I digress. The point I'm trying to make is that even in the linear Open Loop days of the
Mayberry RFD era, when it comes to troubleshooting an engine that's running rough, is the
root cause bad sparks, bad carb, or exhaust valves just a little burned because the lash
was set too tight? Or did the head gasket blow between #5 and #7 cylinder? Everything
affects (and acts like) everything else.
And when we add another layer of complexity on top of all this with Closed Loop operation,
now this whole 'everything affects everything else' behavior is now an order of magnitude
more intertwined. Because the computer can and will compensate (tune around) around a failing
component until it can't hide the issue any longer, so that when the humans decide to stop and
fix it, it really is a hard to decipher convoluted mess.
****
So, as someone who has lived through this engine bay evolution, I am here to tell you that the older
the computer, the
less that it can tell you what's wrong with itself. There wasn't the processing speed
to both tune the motor 100% of the time AND
fully diagnose itself/it's sensors on the fly, the needs of the software
coders were expanding faster than the hardware guys could add additional memory, the emissions standards
were constantly tightening, blah blah blah.
Given all of the above, I can absolutely promise you that in order to troubleshoot your '89 K1500 without using
a wheelbarrow's worth of parts, you really and truly absolutely need a frikkin' computer capable of showing you the live data
in order to finish sorting out your engine bay.
Because, even though your truck is old, it *is* being run in Closed Loop mode. And when it comes right down to it, I can either
perform semi-informed parts guessing with your money, or we can study the captured data, kick around a few ideas, and based on the
sum total of everyone's experience in here we can now figure out how to only change the bad bits. Less frustrating,
more satisfying, less moolah in the long run.
Hope you find the above persuasive.
And remember, the veneer of simplicity is unbroken as long as it's working properly.
But when it doesn't work properly? That's when the underlying complexity breaks through the Simplicity Facade.
:0)
THERE'S A BRIGHT SIDE TO THIS! When the Wife and I attempt to LS swap my 83 Grand Prix, none of that is within the scope of this forum, so you all won't be hearing about that cluster F.
Under EFI control so that you can take advantage of the neat bits like the VVT camshafts? (
VVT)
LS motors do amazing things, mostly due to all the newer/faster/better Closed Loop magic involved. :0)
Q: Why not stop and learn the computer stuff on your truck so that when you do that LS
upgrade you can actually look forward to the computer side of the swap?
Food for thought. Apologies for the length. Computers are cool, but they can also be a bit
inscrutable at first glance.
Cheers --