[Corsa B 1993-2000] Corsa 1.2 16v B cold starting and power issues at 3000+rpm

[lozzer]

Hi,

I've got a Corsa 1.2 16v b X12XE and when I start her cold she has no power, If I wait a minute she drives off fine. Then when I hit 3000+rpm especially up hill the EML comes on and she chokes, lift my foot off and the EML goes off.

I've have had a diagnostic done and the code is P0130(002) O2 Sensor Voltage Low, the voltage meter was jumping all over the place.
Interestingly the automatic diag wouldn't recognise the ECU so had to tell it manually.

I've replaced the temperature sensor & thermostat, but this hasn't made a difference.

I disconnected the MAF sensor, the EML comes on permanently and when I drive the symptoms are the same 3000+rpm chokes

I then reconnected MAF sensor and disconnected the Lamda Sensor, No EML this time! so I drove it around and at 3000+rpm but again she choked but this time the EML came on and stayed on until I reconnected the Lamda Sensor.

Had a compression test on the cylinders and all cylinders recorded just over 100psi (cold engine)

Not sure what to try next? Than you for any advice you can give.

[Taurus]

A few things to bear in mind - the O2 sensor doesn't operate from a cold start until it warms up. Therefore the initial cold start issue isn't the O2 system.

The O2 system is a feedback loop, it is showing either a dud sensor or that the exhaust gases are out of parameter. Once detected the O2 system tells the ECU to alter the fuel mix to correct the exhaust gases - hence the loss of power. But if there is an extraneous cause for the exhaust gases to be out of parameter (eg an air leak in the exhaust, overfuelling etc) then that will throw the same code and symptoms - even though the O2 sensor itself is fine.

The O2 sensor disengages from control of the ECU feeback under full throttle conditions - it has too or else the rich mix needed for acceleration would result in the 'richer' gases causing the feedback loop to come into effect. It is worth testing under full throttle to see if the problem remains - if so it probably isn't the O2 sensor itself.

Note the use of 'probably'. O2 issues can take some checking to figure out.

Try clearing all codes and then disconnecting the EGR, then drive it and see what happens. You'll get the EML on of course, but ignore it. Just see how it drives with the EGR deactivated. (If you can't clear the codes yourself just try it anyway - but clear the codes if possible.)

[lozzer]

Thanks you for the advice Taurus, will update post once I've done this test.

[lozzer]

A few things to bear in mind - the O2 sensor doesn't operate from a cold start until it warms up. Therefore the initial cold start issue isn't the O2 system.

The O2 system is a feedback loop, it is showing either a dud sensor or that the exhaust gases are out of parameter. Once detected the O2 system tells the ECU to alter the fuel mix to correct the exhaust gases - hence the loss of power. But if there is an extraneous cause for the exhaust gases to be out of parameter (eg an air leak in the exhaust, overfuelling etc) then that will throw the same code and symptoms - even though the O2 sensor itself is fine.

The O2 sensor disengages from control of the ECU feeback under full throttle conditions - it has too or else the rich mix needed for acceleration would result in the 'richer' gases causing the feedback loop to come into effect. It is worth testing under full throttle to see if the problem remains - if so it probably isn't the O2 sensor itself.

Note the use of 'probably'. O2 issues can take some checking to figure out.

Try clearing all codes and then disconnecting the EGR, then drive it and see what happens. You'll get the EML on of course, but ignore it. Just see how it drives with the EGR deactivated. (If you can't clear the codes yourself just try it anyway - but clear the codes if possible.)

Hi Taurus

Thanks for your advice, it turns out that the O2 sensor is fine and in fact it was the MAF (Airflow Meter) that was faulty, had it replaced today and it she sounds and feels so sweet, 100% better. I've learn't a lot from this, you need to find an independent mechanic that specialises in your make of car, he will have A. come across your problem a hundred times or more B. have parts that he uses for testing, so saving you a lot of time and money.

So a big thank you to Tony at Mo-tec.com for not just changing the O2 sensor etc....