Misfire Corsa B 1.0 2000

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Re: Misfire Corsa B 1.0 2000

Postby xj40s » Mon Jul 10, 2017 1:07 am

STC - Unless you have something useful to post I would rather you did not post at all.

I have now put 3 waveforms into library.
Cam PS sensor good waveform
Lambda looks a bit rich, variable and sluggish (2 waveforms)
Coolant temp sensor waveform was also good but I did not save it.
All taken by back probing sensor connector. ECU is very difficult to access on X10XE.
X10XE is not fully OBD compatible. Without GM dealer diagnostics you can't access real time data and can only get an abbreviated number of codes.
Will try to get crank PS and MAF tomorrow. TPS is difficult to get at.

I don not think I have any way of finding out the long and short term fuel trims.

The car is only worth about £300 so not worth expense of dealer diagnostics. Nor do I want the expense of a genuine 02 sensor only for the problem to wreck it.
I would like to resolve the issues, as much out of curiosity as anything else. Also wondering why fuel pressure regulator is plumbed in such a manner as to render it inoperative.

BP ultimate is not the problem, the fault just seems to get worse if the car is refuelled repeatedly at the same fuel station, its as if a change in fuel supplier makes the fault occur less often and less severely.
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Re: Misfire Corsa B 1.0 2000

Postby xj40s » Mon Jul 10, 2017 4:19 pm

W541 MAF and Lambda 10 July 2017.psdata
(148.86 KiB) Downloaded 39 times

W541 MAF and Lambda 10 July 2017.psdata
(148.86 KiB) Downloaded 39 times

I am not sure if the above waveforms have attached.

It looks as if the ECU is "correcting" the fuelling about 0.3 volts rich. Does this probably mean the ECU is seeing about 0.3 volts less than I am measuring at the connector.
On the attachment the MAF looks dodgy but I did get some waveforms that showed it to be better. Disconnecting or reconnecting the MAF did not seem to make any difference to the engine running or 02 sensor voltage.

I too find it a nuisance to have to connect the scope to view the waveform library.
I guess I have done something wrong but if I try to open the above attachments they open in picture manager as a small box - can't see waveform.

Cheers
Tony
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Re: Misfire Corsa B 1.0 2000

Postby Technician » Mon Jul 10, 2017 8:57 pm

Tony,

I have a Corsa C with the same fault code as yourself, I have the advantage that I have Tech 2 to check live data and fuel trims, however on the Corsa I have I also have P0135 and P0136, and live data shows the fuel trims as 0% all the time at the moment. Running the engine at 3K the lambda's don't fluctuate much from 450 mv, in fact I might be lucky to see up to 490 mv.

I have just tested the MAF with my scope, I'm not happy with the results of the waveform, very similar to yours, and if I put the cursors on the scope trace I can see initially the voltage rises to around 4.15 V, which would look good on a DMM, but on the scope as I move the cursor across the MAF trace all those vertical lines up and down cycling while the WOT is taking place shows clearly that the ECM is receiving a very poor signal from the MAF to base its calculations on.

The scope trace from the MAF ideally should rise diagonally to a peak of around 4 volts or more, stay there while the WOT takes place and then when you let your foot off the trace should drop diagonally back to the base voltage, there should be no drop outs or glitches, yours and mine are full of glitches during WOT operation.

Now I do have a brand new MAF in the garage somewhere for these cars, if I can find it reasonably quick I'll put it on and scope it to show new Vs old, then you can see the differences, but not today I have now to find it.
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Re: Misfire Corsa B 1.0 2000

Postby liviu2004 » Mon Jul 10, 2017 10:16 pm

WIth an inexpensive opcom, this is what you can see on Corsa B, even the plug is compatible.

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Re: Misfire Corsa B 1.0 2000

Postby STC » Tue Jul 11, 2017 9:17 am

The lambda trace show that it is spending more time in a rich condition than it is lean. That I am satisfied (for now) is effect rather than cause.

My next move would be to Graph Injector Duration alongside lambda to confirm that.

I see MAF voltage at idle at approx. 1.38 volts. I don't like that !
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Re: Misfire Corsa B 1.0 2000

Postby STC » Tue Jul 11, 2017 10:44 pm

Now I do have a brand new MAF in the garage somewhere for these cars,

Drama is that a "NEW" part can be faulty.

To quote JD - Know what to Expect before you Inspect® and certainly before you pull the chain ! As in test the one on the car and KNOW if it is in or out of spec.

You could inadvertently, albeit with good intentions, be adding to the grief.


I would be inclined to bin the Maf and substitute it with a volume switch.
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Re: Misfire Corsa B 1.0 2000

Postby STC » Thu Jul 13, 2017 12:18 am

I have the advantage that I have Tech 2 to check live data and fuel trims,


Sorry to burst the bubble but No! you don't have any advantage !

In the present day having Tech 2 is a disadvantage not an advantage on a 17 year old Corsa.

1. You cannot Graph Multiple Measured Values on a 17 inch screen in colour with Tech2 - Snap on, Kts, Autocom will wipe the floor with Tech2 when it comes to diagnosis and gathering facts in Real Time or very close to.
2. Opcom - No graphed data but a great tool that goes in deep.

Graphing is a powerful tool, even better than the scope in some cases. For example, you cannot scope Desired Values - MAP, MAF, Fuel Pressure.


The scope trace from the MAF ideally should rise diagonally to a peak of around 4 volts or more,


I disagree !!

stay there while the WOT takes place


That would be impossible, given that the sudden opening of the throttle will create a massive change from depression to atmosphere. That change will be a shock, sudden and not sustainable. The huge inrush of air to fill the void will be momentary.
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