How to test if you have a bad MAF sensor
Discussion
I think I have finally defined, by statistical analysis, what is a good MAF and what is a bad MAF
Its all down to how much variation there is in the MAF output in comparison to the engine speed.
In summary a bad MAF gives much more variability at any specific engine speed.
The attached chart shows this quite dramatically. I ran my engine at idle using two MAF's, one which gave me very poor MPG (14 ish) and the other gives good MPG (21 ish)
As you can see the Good MAF has much tighter data distribution vs the Bad MAF.
So what use can be made of this data. If anyone has a suspect MAF all you need do is run the engine up to temperature then once its all stable collect Rover Gauge data for 10 minutes then perform the analysis, Bivariate fit of MAF vs Engine RPM, and see what distribution it gives.
PS If its any use to you, drop me a pm and we can arrange for me to analyse your RG data for you.
Its all down to how much variation there is in the MAF output in comparison to the engine speed.
In summary a bad MAF gives much more variability at any specific engine speed.
The attached chart shows this quite dramatically. I ran my engine at idle using two MAF's, one which gave me very poor MPG (14 ish) and the other gives good MPG (21 ish)
As you can see the Good MAF has much tighter data distribution vs the Bad MAF.
So what use can be made of this data. If anyone has a suspect MAF all you need do is run the engine up to temperature then once its all stable collect Rover Gauge data for 10 minutes then perform the analysis, Bivariate fit of MAF vs Engine RPM, and see what distribution it gives.
PS If its any use to you, drop me a pm and we can arrange for me to analyse your RG data for you.
Great analysis !
Was the only symptom the mpg performance or were there other issues with the faulty maf ?
I recently had to change my maf as the car would only just idle and would not accelerate.
Were you running with cats and lambdas in closed loop for this - it looks like engine speed is between 700 and 1100 rpm?
Was the only symptom the mpg performance or were there other issues with the faulty maf ?
I recently had to change my maf as the car would only just idle and would not accelerate.
Were you running with cats and lambdas in closed loop for this - it looks like engine speed is between 700 and 1100 rpm?
Full decat but with lambdas cnbtrolling trim.
I could not set the base idle as the adjuster screw had little effect on rpm. Also throttle response was unpredictable at times. Revs also dropped to almost stalling approaching junctions.
All those issues now gone.
Software is a bit niche called "jmp" by SAS. Its for statisticians (I was a six sigma black belt so used it a lot)
I could not set the base idle as the adjuster screw had little effect on rpm. Also throttle response was unpredictable at times. Revs also dropped to almost stalling approaching junctions.
All those issues now gone.
Software is a bit niche called "jmp" by SAS. Its for statisticians (I was a six sigma black belt so used it a lot)
I did clean the hotwire with MAF cleaner, made no difference.
So I believe the fault is electronic, ie fried components and thus not repairable, by me anyway.
I would be grateful if you could send me yourr Rover Gauge log file when you can so I can analyse it and compate it to my data.
So I believe the fault is electronic, ie fried components and thus not repairable, by me anyway.
I would be grateful if you could send me yourr Rover Gauge log file when you can so I can analyse it and compate it to my data.
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