MAF readings too high?

[kp7722]

Hi all,

I've had my (unmod'd) '58 1.9TDI Leon for 18 months and have always had a problem whereby when the outside temperature is above 9/10 degrees then I get a hesitation when the turbo kicks in at about 1800rpm. It doesn't always do it but it's just annoying.

Last week I unplugged the MAF for a few days and the problem went away. Plugged it back in and the problem came back. Performance-wise the car didn't feel any different. This all lead my to believe the MAF was at fault.

On Monday I bought a "new" Bosch one from Eurocarparts, fitted it and it ran fine for the next two journeys (about 50 miles in total). Next morning, hesitation is back.

Using torque I thought I'd take some readings of the MAF:

Idle when cold: ~7.5g/s at 900rpm
Idle when warm: ~6.5g/s at 900rpm
2nd gear, WOT: 106-113g/s at ~4300rpm

The car is spec'd at 103bhp which means that the bottom value should be ~82g/s at the most. A reading of 113g/s equates to 141bhp. When idling I thought the value should be around 2.5-3.5g/s?

Thoughts anyone? Another dodgy MAF? Or could it be something else contributing to these high values? Dodgy MAFs normally give low readings, don't they?

Cheers,
Paul.

 

[mike0105]

Sure it's not been mapped? 141bhp is about right from a 1.9TDI stage 1.

 

[kp7722]

I'm presuming not! It was a company car before I bought it from AvailableCar in December 2012. Is there anyway I can tell it's been mapped without access to VAG-COM?

I used torque this morning to give the BHP ("Horsepower at the wheels" reading) and i got it to read 100bhp, flooring it in 2nd. Not sure how accurate this is, or how it's calculated.

 

[Dopedpanda]

Hi all,

I've had my (unmod'd) '58 1.9TDI Leon for 18 months and have always had a problem whereby when the outside temperature is above 9/10 degrees then I get a hesitation when the turbo kicks in at about 1800rpm. It doesn't always do it but it's just annoying.

Last week I unplugged the MAF for a few days and the problem went away. Plugged it back in and the problem came back. Performance-wise the car didn't feel any different. This all lead my to believe the MAF was at fault.

On Monday I bought a "new" Bosch one from Eurocarparts, fitted it and it ran fine for the next two journeys (about 50 miles in total). Next morning, hesitation is back.

Using torque I thought I'd take some readings of the MAF:

Idle when cold: ~7.5g/s at 900rpm
Idle when warm: ~6.5g/s at 900rpm
2nd gear, WOT: 106-113g/s at ~4300rpm

The car is spec'd at 103bhp which means that the bottom value should be ~82g/s at the most. A reading of 113g/s equates to 141bhp. When idling I thought the value should be around 2.5-3.5g/s?

Thoughts anyone? Another dodgy MAF? Or could it be something else contributing to these high values? Dodgy MAFs normally give low readings, don't they?

Cheers,
Paul.

Have seen those loads of times, its most likely the VNT arms in the turbo that is not moving freely.

Have you tried to give it some turbo cleaner?

 

[kp7722]

I haven't. What's the best product/way to do this? I've seen demos of Mr Muscle being used, but is there something a little more "professional" I should be looking at?

Thanks, all, for your responses.

 

[mike0105]

I'm presuming not! It was a company car before I bought it from AvailableCar in December 2012. Is there anyway I can tell it's been mapped without access to VAG-COM?

I used torque this morning to give the BHP ("Horsepower at the wheels" reading) and i got it to read 100bhp, flooring it in 2nd. Not sure how accurate this is, or how it's calculated.

It's not very accurate, more of a guide really. You have to set the weight right and drive on a level road. Probably better in a higher gear as well. By the way. 100whp is roughly 115-117bhp.

Try another run in 4th gear (on a private road of course ) and check the settings on the app, especially car weight and calibrate the accelerometer.

Can you try another 1.9TDI and see if yours is night and day faster?

 

[kp7722]

That's a good point about the weight of the car, etc. I haven't put these values in to Torque. Will do that for my journey home.

I don't know of anyone else with a 1.9TDI so I can't do the comparison. However, if I try to get a more accurate reading of the WHP then this may point to it being mapped. If it's been mapped badly then I suppose this could cause the hesitation as well as the high MAF readings?

 

[kp7722]

Okay, set the weight in Torque, drove home, got 125whp. Something strange going on here. Does this suggest it's been mapped? If so, could this be the reason for the high MAF readings and the hesitation?