S1 V6 auto back on the road at last!! - Problem solved!!

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Dean
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by Dean » Tue Feb 21, 2017 10:14 pm

seems we all have the same thoughts then, i would be looking closely at that O2 sensor tbh.

The sensor generates its own voltage, the more oxygen it gets the lower the voltage, the less oxygen it see's the higher the voltage.
At idle you should see the output fluctuate from near nothing to .9v, if you snap the throttle open you should see some reaction from the sensor in terms of voltage change, if its just sitting at one voltage its just not doing it job, if its doing what it looks like its doing it is constantly reporting a rich mixture although i too am suprised this sensor has the authority to lean the AFR out enough to stop the engine reving.

Did Dave let you borrow the Lexia? can you swap the O2 and repeat the test?

D
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Dieselman
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by Dieselman » Tue Feb 21, 2017 10:25 pm

This should give you an insight to testing the O2 sensor and the open loop rich mixture setting of the ECU.

The ECU won't go closed loop if the coolant sensor, O2 sensor or wiring is faulty.

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Dean
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by Dean » Tue Feb 21, 2017 10:39 pm

If it wont go to closed loop then its stuck in open loop which means its using information from 'look up tables' and selecting an injection timing determind by throttle position, engine speed, air temp and MAP to calculate air volume entering the engine, i would think in this case it would run ok if it was getting the right information and doing its sums correctly but i would expect to see an EML on as the ecu is seeing a problem with the O2 sensor and is choosing to ignore it.
I think what im seeing from the snapshot of live data is the O2 sensor is shouting RICH, and the ECU is holding back the fuel, for some reason the ECU is not seeing high load or WOT and so ISNT going to open loop, its just constantly taking the O2 sensor reading as gospel.
If im not barking up the wrong tree you have a very strange group of at least two problems causing the engine to lean out while thinking it doesnt have a problem.

D
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sdelasal
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by sdelasal » Tue Feb 21, 2017 11:03 pm

Dean, I suspect that you meant to say : at high load or WOT the system is not going OPEN loop - and so ignore the o2 sensor...

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Dean
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by Dean » Tue Feb 21, 2017 11:13 pm

YES! just edited it, good job your on the ball!

D
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by MTXM » Tue Feb 21, 2017 11:19 pm

Many thanks for your various in-depth and helpful comments chaps that I have endeavored to absorb and digest and in brief summary:

Generally:

- I understand the oxygen sensor reading is indicating a rich mix and as I recall there was no fluctuation. The appearance of the plugs and exhaust gases certainly do not seem to bear this out.
- The oxygen sensor has not been changed but the wiring is in order and the heater circuit is certainly working.
- Injector rail pressure has not been checked, although a known good pump was installed above the engine without any change, therefore I do not believe there is an issue.
- I believe it is not that unusual for the Lexia to make mistakes about gears etc., but hopefully the other data can be trusted!

Next steps:

- The throttle position sensor reading can be checked insitu with a meter and in the tests both stationary and at idle the throttle was certainly closed.
- The oxygen sensor could also be changed with a known good sensor and in due course the system retested. Although I did not retain the Lexia I have now purchased my own!

Thank you once again for the advice and I shall let you know how matters progress!

With regards,

Matthew T.
1989 V6 Exclusive (Poland car)
1990 V6sei auto (grey auto)
1990 V6sei manual (gold car)
1990 V6.24 Pallas (Germany car)
1990 V6.24v (Scotland car)
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Dean
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by Dean » Tue Feb 21, 2017 11:21 pm

The lexia does certainly have its uses Matthew and i think if you work on your own cars it is an invaluable peice of equipment as im sure after playing with one today you know.
There should be no sign of rich running on the plugs as the engine is currently running way too lean, its just the O2 sensor is knackered and telling the ecu its running rich, this leans the mixture out hence why the car is not running. I fully expect after changing the O2 sensor to hav to find another issue with one of the sensors responsible for measuring air volume entering the engine.

D
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cxprestigeauto
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by cxprestigeauto » Tue Feb 21, 2017 11:23 pm

Reading this makes me so grateful for my dull, boring, lethargic but reliable 2.0 Si!!!

Good luck Matthew.

Rob
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Dean
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by Dean » Tue Feb 21, 2017 11:31 pm

cxprestigeauto wrote:Reading this makes me so grateful for my dull, boring, lethargic but reliable 2.0 Si!!!

Good luck Matthew.

Rob
Boring and lethargic????? no, no, no. Ample, adequate, sufficient are words i would use. i still maintain the 2.0i is a good perfectly good engine. mine has been fantastic in all these years, i think a conversation with John recently regarding my planned conversion highlighted my insanity to myself when he asked if was worth it, my answer was instant :?

D
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Re: S1 V6 auto back on the road at last!! - fourth time luck

Post by xmexclusive » Tue Feb 21, 2017 11:59 pm

Hi Dean

Someone researching a significant technical project by very interesting and practical trials cannot be insane.
On the other hand having a V6 that only drives in limp mode and refuses to repair could well drive one insane.

Hi Matthew

I expected the ECU to be seeing Throttle values of 0.1v / 0.7v / 1.5volts on those Lexia shots.
The spec is 0-5v linear over 0-6500rpm.

John

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