OK first the questions
1 Does a Corsa C 1.2 16v have a map sensor??
2 If so does it live inside the MAF housing?
3 On a diagnostic programme on the pc how much air would you expect it to show the flow to be under idle and then mid throttle positions.
4 Is there any way of checking them?

OK so to the explanation
No1 sons corsa c 1.2 sxi has had the MIL light on for a while ( but the car runs/pulls fine)
A dtc programme ( proscan) comes up with a dtc of a MAF. the running graph of the airflow shows no movement when using the throttle ( engine running) so we assume its buggered.
We get a new one from ebay ( in a cheap and non marked box/housing but the price is right) and plug it in and clear the codes. the management light goes out and all looks to be well.
BUT when you try to drive the car it is not good. Very light application of the throttle is ok but pushing quickly to mid throttle at any speed or to flat on the throttle at any speed and the car stands on it's nose. It does it every time you change gear as well. Clutch/change gear/ back on throttle and bang it stands on its nose momentarily.
Now i'm thinking the new meter is the wrong one or the map ( if there is one in it) is faulty.
put the old faulty meter back in and she goes ok with the MIL light ON

Ideas welcomed but I suspect the new MAF will need to go back to fleabay anyways.

[Edited on 19/3/10 by omega 24 v6]

Wont have MAP if the management is based on MAF, I dont think. As it's a transient throttle problem have you considered the TPS? But then it'd probably idle funny if the TPS was buggered. Maybe it is just the cheapo MAF, then. Or have you introduced an air leak whilst fitting the new MAF?

Liam

Just a random possibility but has the ecu remapped itself to work with the faulty MAF and needs time to relearn settings or be reset to cope with a working one??

quote:

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Just a random possibility but has the ecu remapped itself to work with the faulty MAF and needs time to relearn settings or be reset to cope with a working one??

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Check the small bore hose vacuum connection to the fuel pressure regulator is OK

Watch the TPS readings using your software --- any jumps in readings indicate a worn out tps, they always wear most in the first 5 to 20% of throttle pedal movement.

It is a Vauxhall so EGR valves are always as possible cause although in this case it would have to be really bad --- easy enough to blank off.

CTS is easy enough to get via live data

Also watch that the lambda sensor output voltage is jumping high and low a few times a second at idle.

A fault in the connection to the crank sensor also might be a possible cause ----

[Edited on 19/3/10 by britishtrident]

[Edited on 19/3/10 by britishtrident]

Thanks for all the replies so far folks.

But again I ask why is it running better with none of the faults using an old faulty MAF rather than a new one ( unless it is also faulty).
Surely talk of TPS and vacuum problems and crank sensors etc etc would also show up big time with the faulty sensor in place.
or am I mising the point some of you are trying to make??

There's a fair chance you've probably got a counterfit component. There's loads of then on e-bay; In other words (to be blunt) you got what you paid for... cheap shit!
I've seen loads of it. Car comes into work running bad. We trace the fault and replace what appears to be a new part and everything runs fine. Customer collects the car and says "but it can't be that, I got a new one last week from e-bay". Lambda sensors, MAF's, cats, you name it...all fake.

adrian

Could well be this Adrian. Maybe too good to be true price wise. Ah well at least its payapl so should be no problem to get a refund. i hope.

gonna see if his mates one is the same and see if he'll let me swap it to see if it works.

I did meter it out and one of the resistances is way different ( can't remember the pin no's now).
i suppose in theory the correct size resistor to put out the MIL would be enough to make it look like it was OK

Don't know if this helps but the most common fault we get on Corsas (and most vauxhalls) is the crank position sensor. Its just above the n/s inner cv joint.