TECHNICAL NOTES ON THE EEC-IV MCU - Auto diagnostics

Eectch98-Part5.fm
To achieve the EPROM files for this setup, burning 400 chips was not required to get
it right, 400 chips were burned to get it PERFECT. More than likely 98% of the world
would never notice the difference in the last 100+, and the first couple of 100 was
figuring out how to do the above.
PS When doing the above settle for the least amount of timing consistent with the
best performance. Trying to run maximum timing results in hitting the knock sensor
and having varying ETs. IF you run too much timing you may have to disable the knock
sensor diagnostics because the car is so happy with yesterdays tuning, and today the
ECM is using the OEM specs and can’t run the diagnostics, and the fault codes get
pinged. (This setup is that way)
Mild Performance Engines, Engine Swaps
Now things take a step up, tools are still the same, but now it would be nice to
have a scan tool, With probably a different cam the operating range of the sweet
spot of the engine has changed, or the weight of the vehicle has. This weight thing
is not to be taken lightly (HOHO HAHA), just had to sneak a little humor in. A
light car and/or one with higher numerically final drive gears will want a lot more
fuel earlier, or more timing taken out sooner. So now you’ll have to have some control
of the timing. But still if you’re using a distributor, you can get by with
just timing at cruise or WOT.
If it’s a mild cam (and if you’re doing this for the first time I would highly suggest
you stay conservative).
Now use your scan tool and look for the magic 128, try adding/subtracting two to
four degrees here and there do the 4d to get a feel for things, and do not use any
WOT testing when going 4 at a time.
Real Fire Breathing Hot Rods
(Things that go lump, lump, rump, rump at idle, have non-lock up converters, and
spin tires in any gear less than overdrive.) This will require modifying such parameters
as Main Fuel Table; WOT enrichments; Main Spark Table; WOT Spark Adders; TPS
Enrichments (sensitivity, duration and quantity); Enable WOT TPS percentage settings;
Cooling fan operation; and Idle speed.
Having the right tools is essential here or the engine will do a basic China Syndrome
Routine meltdown -- and it doesn’t take long at WOT. A code scanner, a DVM,
vacuum gauge, full time fuel pressure gauge (and isolator), and an air-fuel ratio
meter (a DPM or an LED bargraph) are essential and it wouldn’t hurt to have an audible
knock detector.
Ok higher compression, no big shakes Small chamber/AL Heads generally make a difference,
for either less total timing, at WOT
Aluminum Heads need more timing during light throttle cruise, non-lockup converter,
more initial enrichment (due to less drivetrain inertia).
There are several other considerations for the non-lockup converter - including the
extra wear-and-tear on the TCC linings. Since more fuel will be needed earlier, the
% TPS WOT enable must be lowered.
At this level, the instrumentation requires constant attention to prevent damage.
With EFI and knock protection, there is usually protection from things going wrong
but, when things do go wrong, you can’t forecast what the problem will be.
Also, at this level, you might consider running a fuel separator, which is basically
a large tank for the sediment to separate in, so there is no pressure drop due
EEC-IV Technical Notes: Modifications/Upgrades65 last edited: 9/29/98