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Mixture setting on year 2000 996C4

peter roberts

Well-known member
Joined
24 Aug 2015
Messages
47
Coming to the end of a resto of my Techart bodied C4 and it is up for sale.
Some months ago i had the mixture setting reset as it was running very rich. I was advised it needed a run of 20-30 miles for the ECU to "learn" the new setting and sure enough after a run it was obviously running smoother and was very economic. As I rarely use the car the battery has often going totally flat since then and i now find the mixture has reverted to being very rich with lots of black smoke which is likely to put off prospective purchasers.
Is it normal for it to default back to rich with the battery being flat or is there another likely cause.
 
I did not know the mixture could be set as its automatically done by sensors and the ECU. Cant see why a flat battery would cause it to change.

Has the car been mapped? If so, perhaps whoever mapped it can best guide you or anyone else with mapping experience?
 
There isnt a mixture control adjustment , its done via the Lambda sensors , they reset the adaptions by clearing a fault code hence they said give it 30 miles to adjust to normal wear and tear , presumably they replaced or fixed something .

You have a fault which may or may not be related to the previous work that was carryed out .. black smoke would indicate something like a leaking injector or an air mass fault .

You need to have the dme fault codes read out .
 
mixture setting

Thanks for the info, i have arranged for a diagnostic check this week. One suggestion is that the O2 sensors are faulty. Is there any way to check these with a meter?
 
You can use almost any half-decent fault code reader to see if your lamda sensors are working. If they are working then they should be switching voltage in a certain range (I forget what it is, but someone will let you know), and if they are not working there will be a 'not present' or 'implausible' reading from them.

It's absolutely the first place I would start as when the lamdas are faulty the car reverts to a safely rich setting. However, you don't want it running in that state for too long as any unburned fuel will tend to wash the oil off the bores.

Once you've discounted the lamdas then move on to the sensors in the inlet tract.
 
mixture on 996

\thanks for that. I hope my guy with the diagnostic tester can find out tomorrow. One other query. I stripped out the exhaust system 2 years ago and can only remember there being one sensor for each bank. Looking at pelican parts they state there are two. One pre cat and one after cat?
Is my memory that bad that i have forgotten there were four or does a year 2000 have only 2
 
mixture setting 996 C4

Just looked at my PETs list for the car. It shows 4. Before the cat is is 993 606 128 01 and 993 606 118 01 after the cat ?
 

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