Best way to test maf - Alfa Romeo Forum
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(Post Link) post #1 of 9 Old 08-09-13 Thread Starter
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Best way to test maf

I have a hesitation on full throttle in 3rd gear @ approx 4k rpm. 2nd is ok. I would like to check the maf and have licensed copy of multiecuscan. What are the parameters to measure which will help check maf is working correctly? Im thinking desired and actual air quantity but being a novice im not 100%. Car is 159 2.0jtdm with dpf/egr removed by reputable tuner
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The easiest way is to disconnect it and try ... if the hesitation goes, the maf needs replacing.
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great tip gazza. i'll try disconnecting and test
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If you have multiecuscan just log the data.

Select parameters: Engine speed, Intake air quantity, Boost pressure.
Go to Graph and start logging the data.

Then accelerate from 1500rpm to 4000rpm on full throttle in 4th gear.

Save the graph data and post it here...
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Quote:
Originally Posted by TribesMan View Post
If you have multiecuscan just log the data.

Select parameters: Engine speed, Intake air quantity, Boost pressure.
Go to Graph and start logging the data.

Then accelerate from 1500rpm to 4000rpm on full throttle in 4th gear.

Save the graph data and post it here...
Cheers TM. ill log the data and post up tomorrow
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so i ran the test with multiscanecu with / without maf. I am getting dtc p0402 which seems to relate to high air flow quantity. Could this be a by product of the egr being disabled? Interestingly the desired air quantity value remains constant @ 1499... could this be the cause of dtc p0402?

I cleared the fault and had a run with MAF in place and the car didnt stutter but unfortunately i didnt capture the data for the run.
When the error returned i suffered the same hesitation with / without maf. Attached are the stats from the MAF connected run and hesitation was experienced.
Attached Images
File Type: png P0402 dtc.png (46.2 KB, 52 views)
Attached Files
File Type: xls 3rd gear run.xls (23.5 KB, 39 views)

Last edited by 159_kid; 10-09-13 at 14:57.
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If you are getting P0402 with and without the MAF connected then I'd guess it was faulty. Problem with the maf is that it rarely gives an error until it has completely died.

But you shouldn't get the hesitation or lack of revs without it connected ... at least that's what happens on a petrol.

You have checked for splits/cracks in the intake pipe work?
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The fault indicated is airflow related and due to maf disconnection. Just drive the car to feel for hesitation and if it is gone then the maf will be the problem. If it is still there then the maf will be ok and some other fault will be present. Yhe engine responds to direct conditions instantaneously so if the maf gives a false reading and fueling is reduced it is seen as a normal funcrion and no fault will be indicated.
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(Post Link) post #9 of 9 Old 16-09-13 Thread Starter
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The code was received wen MAF was connected... i cleared the code and it returned. I have given the MAF a clean but the hesitation is still there in 3rd gear @ approx 3750rpm. I find it strange how its only in 3rd gear?
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