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Re: I guess the real follow-up question is... Posted by SWEDECAR [Email]  (#112)  [Profile/Gallery]
(more from SWEDECAR) on Thu, 14 Jul 2011 16:52:59
In Reply to: I guess the real follow-up question is..., nwas, Thu, 14 Jul 2011 16:02:53 Members do not see ads below this line. - Help Keep This Site Online - Signup |
With the Tech 2 scanner you can monitor something called Air mass meter deviation value which is a computed value by the Trionic ECU using many difference sensor like boost sensors, air mass meter, O2 sensors and throttle inputs.
If that value drops negative during steady acceleration you have a lean condition building that can lead to knocking/pinging. But it is also a lot of other things than an air mass meter that can lead to a lean condition so that value is only as good as the tech looking at it and decipher what it can come from.
This piston came out of a 9-3 equipped with K&N air filter. When I was done with the job and test drove the car I thought all four piston were going to come out again through the block again from the massive pinging the engine created. Looking at the air mass deviation values it was down around -20 or so (+-25 is the limit).
Spray cleaning the air mass meter element brought the value up to about -10 and the customer was happy enough since he was going to sell the car anyway.
The air mass meters goes bad even without the help of K&N filters and they do it very quietly over a long period of time lulling you in to believe that nothing is wrong until you suddenly step on the throttle to pass another car or going uphill somewhere and maybe during a stinking hot day and that you at the same time got a bad batch of gasoline or filled up with 87 instead of 91 since you didn't have enough money.
When all the stars are lined up, that's when things like this happens.
Anders
, Thu, 14 Jul 2011 16:52:59 <-- Viewing This Message
, Fri, 15 Jul 2011 17:00:04, Thu, 14 Jul 2011 20:14:43, Thu, 14 Jul 2011 08:43:02
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