Mentioned this before on this site and my car has been running perfectly the past 300 miles but was crossing major junction today and the engine did not respond to that I was increasing preasure on the throttle, it was quite scary.
I've checked the thottle cable and it seems to be fine so I am suspecting an AFM fault. There is no ECU fault codes but apparantly on the 1.2 16v faulty AFMs usualy do not show a fault unless its very bad. The other sting is that people have had ECU problems resulting in cheap after market AFMs so it is advised to use a Bosch one but they are £100.
Is there anyway of testing the AFM before replacing it and hoping for the best?
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simple answer is no, when i ever i have looked at the live data i cant spot anything wrong with the figures i usually go on gut feeling and how it drives but i have the luxury of haveing a store full of parts to choose from, that said i cant just go throwing things at it without a good reason,Regards TB ps they don't usually give a sudden power loss they gradually fade away (maf's that is)
Edited by topbloke on 12/06/2009 at 21:40
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The odd thing is 99% the car drives perfectly but this sudden power loss has happened a few times now to make it an issue. Could it just be simply the cable? It does look ok but I suppose they can get jammed?
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>>when i ever i have looked at the live data i cant spot anything wrong with the figures
Yes, I helped the Vauxhall garage where I used to work find one of their first MAF problems which they were struggling with. We found the live data were absolutely fine, and, in truth, it was a bit of a fluke that I found the problem - I partially blocked part of the inlet to the MAF and the car suddenly ran better!
Much later, the coin fell. It isn't the magnitude of the signal that's wrong - it's the phase of the signal relative to the engine cycle that's wrong.
As the MAF is a thermal device,the temperature changes take a certain amount of time, and the ECU can compensate for that as it tots up how much air is going into each cylinder (obviously, the ECU knows when the valves are opening and closing, and has some idea about the manifold dynamics). If the MAF becomes contaminated the time it takes for the temperature to change wil change, and screw up the ECU's sums. However, the averaged value which you see on Tech1 or Tech2 is sampled and averaged much much more slowly than happens inside the ECU. One way to see it is to put the MAF output onto an oscilloscope, and overlay some timing marker, say No 1 injector pulse - you'll see a different time lag between traces for a good and bad sensor. Unless you have a previously stored good and bad trace to work from though it's utterly useless as a means of diagnosis!
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ive bought at least 4 mafs in the last 4 months
2 from the factors at 65 quid each
2 from the internet at less than 30 quid
one of the factors ones even said on it boxed for bosch
ive had no come back from any of these cars (touch plastic) so as far as im concerned so long as you plug it in correctly and you dont have resisters in iats etc or carrots in front of your bumper to make your corsa go faster i would buy the internet one,the guy delivers quick
my only concern is a maf might work on one car but be out of parameter on another so a genuine bosch one might be better if you intend keeping the car a long time and eurocarparts did want 100 quid for a bosch one when i phoned them and 55 quid for a copy
the choice as they say------------
one final thing dont buy a scrappy one as they seem to go off if the car has been stood a while
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Bellboy does it sound like it is the AFM to you? My garage is having a 'quick look' tomorrow to adjust the clutch cable (the pedal is sinking to the floor)and just to check the throttle cable is ok.
Bellboy the problem is also many people don't realise there is a fault so just because you have had no come back it dosn't always mean there isn't a fault with it. From the Corsa sites the people who have had trouble with their AFMs usualy tend to have done silly things like drill holes in their airbox.
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>>does it sound like it is the AFM to you?
Although I'm clearly not BB, I don't think that you have an air flow meter problem.
Lack of response to throttle can be many things, and I would be tempted to check the high tension ignition system first.
I would also try to avoid poke and hope diagnosis. Pay someone who is competent to find the fault.
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Not sure, I don't want to go down the VX route as I could probably buy all the sensors for what they would charge. I had a fault code red on it last week and no fault codes were returned, he has a decent system too not one of the cheap DIY things but even then I know they don't always pick up faults.
The thing is most the time the car is very very smooth, there is no issues with miss fires etc, it generaly drives like a new car then when you least expect it suddenly looses power for a second then when I put more preasure on it it works normaly again. I would say it does it when accelerating quickly as it always seems to be the same junction it happens on.
By high tension ignition system do you mean the coil pack? There are no HT leads on this engine, a coil just sits above each plug so the ignition is actually very simple. I can see this costing £100's if its not the MAF :(. The spark plugs are also fairly new as is the air filter.
My mechanic reckons the injectors could be dirty would this also cause a sudden lack of power?
NC Didn't mean to exclude you, just asked BB because he has replaced a lot of MAF sensors on my engine and just wondered why he had to replace them. BB is a Corsa expert and you're the resident fuel injection expert so a perfect mix :).
Edited by Rattle on 12/06/2009 at 23:21
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This is the other thread I made on this issue around 500 miles ago, I am now used to the car and I have replaced the petrol cap with a genuine GM one which has stopped the pinking.
www.honestjohn.co.uk/forum/post/index.htm?t=74419
The two things which keep coming up are the EGR and the AFM/MAF.
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i use a Sykes-Pickavant ACR4 with the latest pod for corsa"s it wasnt cheap
but never picks up the maf as a faulty component ,it does flag other codes but i have learnt now to ignore them for these particular engines as they come up due to the sudden loss of power under load,you can look at live data and sometimes as i said it can be out of parameter which helps,i must also add that the eml nearly always comes on though if you try to drive through flat spot
ive not yet had a problem with the egr on these but im sure i will in time as its a silly place for them and they sit on a water jacket
every corsa ive had the maf has cured the problem,i didnt reply because it was said my customers wouldnt know a toadstool from a mushroom and that is why non of these cars can back
no offence anyone
as for checking them the best way is by substitution
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Oops sorry if I caused offence there. I just meant that people don't always bother to complain/notice thicks not that your customers are thick. I sometimes do a job and a customer tells me 6 months later it didn't fix it, I just think I wish you had told me earlier as there is nothing worse than a customer potentialy not being happy.
I will get that throttle cable checked out tomorrow while he does the clutch cable (pedal is down to the floor which cannot be normal) if he still can't find anything I might just risk £60 and replace the MAF myself, I have taken out the MAF on my dads Fiesta so I can't see it being much different.
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there in lies the problem the bean counters wont invest in the kit and i ain't buying it with my hard earned cash so they can get richer, been trying for ages to find a tech32/fluke meter at a reasonable price but its crazy money, ultimatly it will help me but there are things i/we need and things that we would like and i will only work with the tools that they supply,Regards TB
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