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Ok, just did the scan.

First, Vikash, AWESOME program, thanks man!

On to business.

System Voltage: 13.6v
Engine Speed: 1275RPM to 1375RPM
Coolant Temp: 198 degrees
Ignition Timing: 15 degrees BTDC
Air Flow Signal: 1.64v to 1.66v
Load: 54 - 58
Throttle Position Signal: 4.68v
Injector Pulse Width: 3.584v - 3.712v
IAC Valve Duty Cycle: 20%
O2 Sensor Signal: .18v
Fuel Trim: (this is weird). 0.00% at "idle", tap the gas and let it come down to "idle", and it reads 19.53%.
Timing Correction: 0 degrees
Boost Control Duty Cycle: 83.59%
Barometric Pressure: 751.25 Torr
Boost/Vac: -15.8 inHg (starting fluid shows no VAC leak though...)

The others aren't important (Input Switches, I/O Switches, and ROM ID).

How do they look? VAC seems low, load seems high, obviously idle is high, and air flow is high as result of high idle.

I need help ASAP guys!

Thanks!

Off the top of my head, these are the comments I think of:

- Your engine speed looks a little high. Might want to correct that.
- Did the scantool actually say the injector pulse width was measured in volts, or was that a typo? If the software said that it's a bug I should fix...
- Does the oyxgen sensor signal stay pretty constantly around 0.18 volts? That's weird. Since the engine is warmed up and idling it should be in closed loop, so that signal ought to be cycling up and down. 0.18 volts is a relatively lean signal, too... Hmm.
- That does seem to be weird behavior for the fuel trim too... Hmm.
- The boost control duty cycle is high, but that's due to the high engine speed.
- Does your manifold pressure gauge corroborate the relatively low vacuum reading? I'd actually expect you to read higher-than-usual vacuum if idling too high...
- It looks like your IAC duty cycle is about right.

Have you tried running without the oxygen sensor? There seem to be indications that your problem might be with the air/fuel ratio learning system or somthing. It's really easy to unplug as long as the exhaust isn't hot.

Otherwise, it seems like you're just getting too much air in there somehow. I forget -- have you tried swapping to a known-good untampered-with throttle body?

How do I unplug the O2 sensor?

I think I've got exactly the same problem that Matt does. My idle was jumping around 700 to 1000 periodically and was acting REALLY weird. I didn't get a chance to scantool it when it was doing that though.

Oh, Injector pulse width isn't in volts, that was my bad.

So when you tested it the oxygen sensor voltage was indeed staying around 0.18 volts the whole time? That definitely is wrong for a warm engine idling.

Disconnecting the sensor isn't hard:

-First disconnect the negative terminal of the battery with a 10mm wrench. Then press the brake pedal for 30 seconds with the ignition switch on; that'll help make sure the ECU resets.

-Then locate the oxygen sensor. It's threaded into the downpipe just downstream of the turbine, hard to miss.

-Follow its electrical harness for several inches until you reach the rectangular connector.

-The connector has a locking tab that you have to lift up (not push down) to release the connection. Use a small slot-head screwdriver or something to disengage that tab.

-While the locking tab is lifted, pull. You'll probably have to pull fairly hard if the connectors have never been separated before.

-Ziptie the connectors out of the way so they don't accidentally get caught anywhere or touch the exhaust.

-Reconnect the negative terminal of the battery, and start the car, preferably with the scan tool hooked up.

-Make observations.

Awesome, I'll go do that right now.

If it acts normally when the 02 sensor is unplugged, then what's the problem? Bad 02 sensor?

Hehhe... you're calling it a "zero-two" sensor...

Yes, if it acts normal without the sensor connected then we have a strong reason to suspect a faulty sensor.

Just unpluged the O2 sensor and restarted the car.

Still throwing the same code, nothing changed.

Fuel trim is steady at 0%, O2 sensor signal is .30 to .31 volts.

Vac is still in the -14 to -15 range.

I need to get another can of starting fluid and see if I might have missed anything. I also need to remove my uber ghetto boost gauge. I wouldn't be surprised if that was the cause of my heartache.

What? It's still reading an oxygen sensor signal?! And the signal is varying?!?!!!

That is definitely wrong.

I wonder if you've got the oxygen sensor signal wire crossed with something somewhere on its way from the ECU harness connector to the sensor harness connector.

Do you feel like removing the oxygen sensor pin contact from the ECU's connector? Or are you daring enough to try snipping the wire?

Hey Phil, I want to scan my car too! I really want to see what I've got going on.

Cool deal, I am about to go to Radio Shack and get some solder and make a connector for this program. It's a bit to difficult to just insert the wires.

When can you come over this week? I'm off work until Thursday, but I'm working tomorrow night at 8:30, and I'm going out on Wednesday night at 10. I work until 6pm on Thursday and Friday.

I'm going to make my adapter and then go run the scan tool again.

What's weird about the O2 sensor still showing voltage is that the car throws the code 32, which is the O2 sensor inoperative code. The ECU know's that the O2 sensor is unplugged.

If I get off early tomorrow, maybe then. If not then then probably Wed. Today sucked at work so I'm really tired...

Cool, I just soldered a connector to the cable. Plug and play . I raped the connector out of my stock radio.

Just gotta electrical tape it up a bit so it's a wee bit more sturdy.

BAC5.2 wrote:I raped the connector out of my stock radio.

Nicely done.

Now with that hacking experience, do you feel ready to try removing the oxygen sensor contact from your ECU's wiring harness?

How involved is it? Like what would I have to do? I'd rather snip a wire than de-solder anything.

As for my custom plug-n-play adapter...

Nice cable.

It wouldn't be desoldering; you just need to disengage some plastic locking tabs. We talked about it recently in this thread:
http://bbs.legacycentral.org/viewtopic.php?t=16806

THAWA ended up just cutting the wire too.

If you cut the wire, then I guess you're just setting yourself up to replace it with a new wire anyway, which might end up being necessary if it turns out that cutting the wire helps.

So where do I find this tab? I'm about to go outside and do a scantool test again, to make sure my connector works and everything.

Oh, and I was talking to a distributor friend of mine with a Japanese contact. I can't remember the company at the moment, but they make ECU's for the BC5.

Anyway, I'm going to ask him about the Hitachi OEM BC6 ECU pinout's. See what he can come up with. I'll keep you posted. Apparently he has a very strong interest in all BC/BF cars (be it 5 or 6).

Cool, huh?

It should be pretty clear when you look at the connectors. The first tab locks across the entire row of pins and is easily visible. The second one is just for that one pin and is most easily reached by sticking your needle/screwdriver/contact-extractor in from the side that the ECU's pin normally goes.

That's cool, let me know what your friend finds. I assume you're talking about the pinouts of the chips inside the ECU, right?

Yea, I meant the pinouts of the chips inside the ECU.

I don't think I quite follow what you are saying about the tabs.

Did you look at the connectors and it still didn't make sense?

MK, maybe you can explain it better than I can... If you see this thread.

Vikash is dead on with the description. But i'll try

Using a safety pin, take the ecu wire side connector and give it a good look. Like v said there's a part for each side that holds all the pins at the top. It is secured by a small tab on each side of the connector. What i did was pry the tab on one side, move the part spanning the connector out a bit, then pryed the tab on the other side. This let the piece fold off the pins.

Then look into the hole the ecu's pin would go. You will see teh wire is held in by a plastic tab that engages the small metal piece that's on the wire itself. If you stick the safety pin into the connector you can get the tab to disengage and pull the wire right out of the connector.

Snap the piece that folded over back into place (assuming the fix worked for you) and you're golden.

MK

I haven't even looked yet. I'll do it tomorrow.

Thanks guys!

In the inset picture, look at the top of the connector near the wires (on the narrow part). yoou can see two small indents. There are two on each side, and the two on corresponding opposite sides are what you have to bend a tad to get the ridge that goes across to fold down

MK

I know exactly what you guys are talking about now, but I don't know which pin I need to pull to remove the O2 sensor from the ECU.

Any input?