Andre Hedrick

How does one test the state of the ECU unit under thood on the pass side near the 14-pin monster?

I failed smog on HC and CO, how can one lean the car out?

MY 81 US non-S.

IcemanG17

typically when a 928 fails both HC and NOX (but you failed CO) it points to a bad cat.....since essentially the engine is rich and lean at the same time.....I am not sure with CO means?

Was the engine properly warmed up?
The weather yesterday was TOO COLD, which makes things rich

I am guessing your car is too rich......wait till a hot day, run the car HARD HARD HARD to get temp in the cat and re-test.....

Sharky barely passed smog on a cold day, when it sat for almost an hour waiting at the smog shop.....two years later on a hot day it passed with ease....zero changes to the car in the two years

Mrmerlin

have you checked the O2 sensor if its original then you should replace it
Plugs what brand and what rating are they?
Ignition wires are they fresh?
Air cleaner is it fresh?
Oil and filter is it fresh?
Vacuum leaks are the lines fresh? if not replace.
Have the timing marks been verified?
Does the vacuum advance work and is it connected correctly?
did you add some Techron to the fuel? if not then add some.
Battery connections are they clean?
Is there a cat on the exhaust?
These would be things to look at first, i dont know how you would check the computer,
but if the rest of the parts are old then they could cause these issues

GregBBRD

^^^^^^ Good info. Stan is a very smart guy. I wish he lived here. I could keep him busy 80 hours a week.

Here's the answers to your questions:

If the car runs....it's good!

C/D units either work...or they don't.

What were the numbers on CO and HC?

CO tells you it is too rich and HC tells you it has a mis-fire. If extremely rich, the HC can go up.

You can lean down these cars by removing the "barn door" assembly. Remove the cover and "tighten" the door, so it opens slower with the same amount of airflow (tighten the spring.) Mark the plastic wheel (with all the teeth), before you start. Just lift up the metal retainer...making sure the spring doesn't "unwind" the plastic wheel (which is why you mark it.) Depending on how much you need to lean it down will determine how far you turn it.

Andre Hedrick

Oil fresh
Wire, Cap, Rotor fresh
E3.46 plugs new, 1 day old before SMOG
Air Filter less than 6K
Smog Filter less than 3K
Vacuum lines all present, attached, rubber, and less than 3 years
Timing dead on 23 at 3000 rpms
Techron added two tanks ago, and filled with Chevron since.
Battery clean, tight and lives on a trickle charger.
Barn Door rebuilt from 928Intl 3 years ago.
TB/WP 4000 miles ago
New ECU Brain 04, came with 02

CAT and O2 are original, new ones have been ordered

Fuel rail pressure 47-52 pounds.
Injector harness rebuilt with new Bosch connectors.
Temp II checked two years ago
PK Tensioner first smog event
Old Bosch plugs were yello/brown
Tops of pistons were clean and shiny.

Mrmerlin

Thanks for that bit of info Greg,
I didnt know the barn door could be adjusted.

In that case before you would adjust the barn door replace the O2 sensor first,
and double check the vacuum lines are good,
and run the car in the dark with the air tubes removed looking for jumping sparks.
If the O2 sensor and new cats dont solve the condition,
then adjust the barn door,
BUT since you have replaced it with another unit this would be the last thing to mess with

IcemanG17

Andre
Your cat is dying....your NOX numbers are far too high as well

Also your fuel pressure is high...at idle you should be 29ish....max should be no more than 40psi..... Do you have an adjustable fuel pressure regulator?

GregBBRD

There's actually a few adjustments that you can make. There's also an adjsutment on the arm that sweeps across that circuit board that can be changed. So, you can "loosen" the spring some, to give the vehicle more fuel for a given airflow and then "tweak" back the arm to lean down the mixture at idle.

The 1.8 914s came with a barn door meter that always warped and had to be replaced. The "replacement" units had to be lean enough to work on any vehicle and not have excessive fuel, so they all came so lean that you could hardly make them run without messing with the spring pressure.

Mark Anderson

If you end up needing a cat a have some new factory cats being shipped via ocean as we speak.

brutus

Be real careful about what cats you buy for use in California they MUST be approved for use have a carb # . If you check on line you will see most are 49 state approved and parts houses will not sell none approved cats to Ca customers, why you ask ? There have been some six figure fines paid by mail order companies who did.
So universal or high flow cats approved for California now cost two to three times what they do for what appear to be similar cats for other states. Some smog test stations will look for the carb # !!

GregBBRD

Of course, looking for the "number" is silly...because there were "approved" cats, in California, before this most recent "law to help your buddy/relative/person giving you cash make more money" was passed.....

Andre Hedrick

OUCH, I just dropped $450 for one that has CARB numbers on it.

I might need a pair of regulators @ 2.5 bar if mine are toast or they are 3.5 bar for some reason.

Brian,

20" of vacuum on the front fuel dampner @ idle and 47 psi on the rail.
If I draw 25" in the dampner there is no change.
Will have to try the regulators on the back next.

Mark Anderson

Our new factory units should cost about the same.

Andre Hedrick

Zero vacuum is 52-55 psi
25" of vacuum is 42 psi so my regulators of out of spec.

Does anyone have a pair handy I can test and use for smog?

Andre Hedrick

Is there a detail instruction on how to do this?
My MAF from 928Intl currently and it is the one causing it to go rich.
I have another one, but which one to crack open?
The rail gauge had an 18psi high bias, that has been fixed.
The two regulators are now new and the gauge no longer bounces and on zero vacuum it read 36psi now and with vacuum it is 29psi spot on.
Added a FAZE air fuel gauge w/ the new O2 and managed to fix the idle to high side of ideal, but running it is no longer smoke blue(led) rich it is two off max.

Good thing I did the regulators as their vacuum side stinks of fuel, and the hose just crumbled in my hand when removing them. They must have been original.