Disconnect MAF impact on LTFT and other warning lights?

[MrBigglesworth]

Disconnected my MAF and ran the car for a short while and noticed the following:
- TMPS warning came on
- ESP/ESC light came on
- in MAF reading was around 363g/s
- the on throttle (i.e. mult) LTFT rose from c.10% to c.18%

Is this all normal behavior?

Don't suppose anyone would be able to do the same and check the MAF reading and LTFT impact of driving for 30 mins with the MAF disconnected?

Cheers

[Van Black]

May I ask why you chose to do this?

[Audiian24]

Esp light is normal. Did u do this to boost more? Lol


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[Charles.waite]

WHen you unplug the MAF your ECU goes into default mode or whatever you want to call it and the dash generally lights up like a christmas tree.

[MrBigglesworth]

May I ask why you chose to do this?

I was trying to chase down a slightly high throttle mult ltft, person I want to remap suggested I try this (also changed maf, o2 sensor, hp sensor, fuel filter, n80 recently, no leak in TIP and the idle/adap ltft is spot on). Car actually boosts fine but before start putting extra load on car, I wanted to see if I could get everything nicely in spec.

[MrBigglesworth]

WHen you unplug the MAF your ECU goes into default mode or whatever you want to call it and the dash generally lights up like a christmas tree.

Ah ok, I thought the lights on might be normal.

Anyone able to add their own observations on the LTFT - or even better anyone willing to try this and add their findings?

[Van Black]

I was trying to chase down a slightly high throttle mult ltft, person I want to remap suggested I try this (also changed maf, o2 sensor, hp sensor, fuel filter, n80 recently, no leak in TIP and the idle/adap ltft is spot on). Car actually boosts fine but before start putting extra load on car, I wanted to see if I could get everything nicely in spec.

You can reset the throttle body adaptation, if that's what you're looking into. Can't help with VAGCOM info since I don't have one, but Charles is right, when you unplug a sensor the ECU goes into failure mode and automatically sets a default value for said sensor, so unplugging the MAF won't do much. I think you're better of recording what all the sensors read during normal drive and check against target values.

[MrBigglesworth]

You can reset the throttle body adaptation, if that's what you're looking into. Can't help with VAGCOM info since I don't have one, but Charles is right, when you unplug a sensor the ECU goes into failure mode and automatically sets a default value for said sensor, so unplugging the MAF won't do much. I think you're better of recording what all the sensors read during normal drive and check against target values.

Done throttle body adaptation and logging during normal driving. Just looking for a refernce point for the ltft change when MAF disconnected.

[Van Black]

Done throttle body adaptation and logging during normal driving. Just looking for a refernce point for the ltft change when MAF disconnected.

Could you explain what you mean by LTFT? I don't know this abbreviation

[p0isin]

Long term fuel trim

[Van Black]

Okay then, 10% on the LTFT seems a bit high...I've been looking into this and apparently the ECU doesn't shoot an error until it reaches 25% +/-.
Also, the tech say it should be around 0% -> +/- 3%.
Did you check your O2 sensors? Also check for leaks on the intake side, PCV valve and intercoolers. A small leak could cause the system to read
too lean and add fuel to compensate.

[MrBigglesworth]

Okay then, 10% on the LTFT seems a bit high...I've been looking into this and apparently the ECU doesn't shoot an error until it reaches 25% +/-.
Also, the tech say it should be around 0% -> +/- 3%.
Did you check your O2 sensors? Also check for leaks on the intake side, PCV valve and intercoolers. A small leak could cause the system to read
too lean and add fuel to compensate.

You are right, it is slightly out of spec, nothing catastrophic, but that's why I am trying to see if it can be rectified.

Mentioned earlier that I've changed the O2 sensor and tested the turbo intake pipe alreadyfor leaks. Way I see it, leak after the turbo would cause a boost leak and it would run rich not lean.

Forgot to mention that PCV was also changed last year, and rocker cover gasket too.

I'm curious about the result I got on disconnecting the MAF. I expected it to not really change or actually go rich as I had read that the default ecu maps were meant to run slightly rich for safety. It getting more lean made me wonder if something else is still inputting and that causes it go leaner. Not sure what this. From some reading today I am wondering if the MAP sensor could be doing it?

[Charles.waite]

Why would you care about the LTFT while the MAF is unplugged though?

[MrBigglesworth]

Why would you care about the LTFT while the MAF is unplugged though?

I just thought it was a strange result and may give me some useful information about the underlying issue - which is why I was hoping I could get a reference from someone else who has done this/can do this to see if it is actually normal or not.

[Van Black]

I've got a shot intercooler and the error I get it AFR too lean at idle. It doesn't seem to affect the load too much. It's worth
giving it a look, rocks tend to fly in the air intake for the IC.

[MrBigglesworth]

I've got a shot intercooler and the error I get it AFR too lean at idle. It doesn't seem to affect the load too much. It's worth
giving it a look, rocks tend to fly in the air intake for the IC.

Thanks, but the way I see it is that if you had an intercooler with some kind of leak then it would suck in air under vacuum (hence lean at idle), but it would be losing air when under boost (or rich under throttle) . I have very in spec idle performance (LTFT is 0% +/- 1%), but lean on throttle performance - so the symptoms don't match your cause - although I may not be understanding everything correctly!

[Van Black]

Thanks, but the way I see it is that if you had an intercooler with some kind of leak then it would suck in air under vacuum (hence lean at idle), but it would be losing air when under boost (or rich under throttle) . I have very in spec idle performance (LTFT is 0% +/- 1%), but lean on throttle performance - so the symptoms don't match your cause - although I may not be understanding everything correctly!

You're right, in you're case it looks more like a fuel system problem, like injectors not closing properly or fast enough.
I doubt the HPFP or regulator valve could cause this, I believe the ECU would be able to trim a too high pressure in the rail.

[MrBigglesworth]

You're right, in you're case it looks more like a fuel system problem, like injectors not closing properly or fast enough.
I doubt the HPFP or regulator valve could cause this, I believe the ECU would be able to trim a too high pressure in the rail.

Yeah - injectors are on my watch list - need to get them scoped or something!

[Van Black]

Can't think of anything else.
Maybe keep us posted on the progress.

Best of luck!

[p310b]

Disconnected my MAF and ran the car for a short while and noticed the following:
- TMPS warning came on
- ESP/ESC light came on
- in MAF reading was around 363g/s
- the on throttle (i.e. mult) LTFT rose from c.10% to c.18%

Is this all normal behavior?

Don't suppose anyone would be able to do the same and check the MAF reading and LTFT impact of driving for 30 mins with the MAF disconnected?

Cheers

So if I might be able to help you, I will just pop off my MAF sensor then log while drive it for 30mins? May I know under which block do you want me to log it for you?


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[MrBigglesworth]

So if I might be able to help you, I will just pop off my MAF sensor then log while drive it for 30mins? May I know under which block do you want me to log it for you?


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That would be great and yes - its basically popping the lead off the MAF sensor and then driving for 20-30 mins (normal/slightly easier than normal driving I would say) and seeing what block 32 measuring block values were before and after you did this.

Also is you 2.0T stock? With the MAF connected as normal, can you please let me know what you get on block 2 measuring block values for the MAF (in g/s) under a wide open throttle run (peak value doing a saved data log).

Cheers

[p310b]

That would be great and yes - its basically popping the lead off the MAF sensor and then driving for 20-30 mins (normal/slightly easier than normal driving I would say) and seeing what block 32 measuring block values were before and after you did this.

Also is you 2.0T stock? With the MAF connected as normal, can you please let me know what you get on block 2 measuring block values for the MAF (in g/s) under a wide open throttle run (peak value doing a saved data log).

Cheers

Hi, i did the log, do you have email for me to send?


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[MrBigglesworth]

Hi, i did the log, do you have email for me to send?


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I've messaged you. Big thanks!