Thomas Owen

Hello everyone,

I have my engine running on a test stand while the car is being completed. Here is the current configuration of the engine:

Stock intake
Cone filter
all new fuel injectors - tested
light weight flywheel
B&B headers
New pistons and cylinders
ECU jumper in place for "USA Japan with Cat Converter" (so O sensor is in the loop)
.03 ECU with Steve Wong chip

So, here are the symptoms:

- engine starts immediately with a touch of the key
- no faults or errors
- idle is perfect
- about 60-90 seconds in it begins to idle very rough and smoke (rich)
- Put stock chip back in and same symptoms.

It appears to go into open loop.
- So, I replaced O sensor and symptoms the same
- monitor voltages from O sensor and it points to 'very rich'.
- Disconnect O sensor and no CEL or error appears. This seems odd to me. Can someone confirm that I should get the light by unplugging the sensor?

Now, if I change the ECU jumper so that it corresponds to "Manual trans without Cat converter" the engine runs fine. This eliminates to O sensor from the system.

I have checked all wiring to ECU for the O sensor - all ok

It just comes down to the ECU seems to not recognize the signal from the O sensor.
Should I just leave the O sensor out?

My guess is that there is something internal in the ECU that is the problem -

Any thoughts?

-nick

Both coding plugs should have no jumpers for "USA Japan with Cat Converter".

Which pins are you putting the jumper on? If you are jumping the 3-pin to ground, then you're getting open-loop always. If you're jumping it to +12v, then you're getting the Japan map that uses a cat temp sensor. I'm not sure what the latter mode looks at/for. Sounds like you are jumping to ground. Which would explain why there's no cel when you unplug the o2 sensor- the ecu isn't expecting one!

Thomas Owen

My jumper chart may be off so this is what I have:

- Manual trans with cat, Except USA and Japan - open

- Manual trans, USA and Japan - jumper to 12v

- Manual trans without cat - jumper to ground

So I put the jumper to 12v and get the rough idle etc after 90 seconds. I put the jumper To ground and it runs fine but I assume no O sensor.


Am I off here? What should I have for the use of O sensor?

Thomas Owen

Found a post by Bill Verberg...


1. for 964 manual w/ cat - 2 pin is open and the 3 pin is open
(all USA except California)


2. for 964 manual Japan the 2 pin is open and the 3 pin is bridged to battery+ w/ 928.607.421.00


3. for manual w/o cat the 2 is open and the 3 pin is bridged against ground w/ 928.607.422.00

So it looks like I need to open up everything and the O sensor should work (and give a cel when disconnected).

Thanks

Thomas Owen

Here is an update:

after making sure that both the 2 pin and 3 pin connectors were open, I started the engine and let it run for a couple minutes.

I then unplugged the oxygen sensor and the Check Engine light did not come on.
Can someone confirm that this should happen? i can get any other fault and clear it.

Thanks,
Thomas

JasonAndreas

Take a look at THIS THREAD! To switch to the USA fueling maps and have the ECU pay attention to the O2 sensor requires a jumper to 12V+ using 928.607.421.00. The way you are setup now will set the ECU to ROW + CAT. Does your check engine light illuminate when you disconnect other sensors? Have you tried going back to the stock chip?