MAP sensor not plugged in to anything?!?! MK4 GTI, 1.8T, SMIC,

[kendog]

Hi All!

I'm really hoping someone can shed light on this 'issue' I found..

Basically, I have MK4 Golf GTI, with 1.8T AGU engine. I have an APR Stage 1 map, but the rest of the engine is stock.

I was looking in my engine bay, on the drivers side, down between the window washer bottle and the back of the drivers side headlight, to where I can see the top of the ****ty SMIC... and what I noticed is what appears to be the MAP sensor plug, but with nothing plugged into it... and for the life of me, I can't see any spare wiring that isn't plugged in to anything ...?!?!?!

I do not have my VCDS set up at the moment (I had to reformat my mac), so cannot check for errors, but I had previously been checking every couple of months after the 1.8T engine conversion, with no error codes (except for the drivers side heated mirror which isn't heated).

Can anyone shed any light on this? If it's been like this since the engine install, why there were no engine fault codes? Could this be why I seem to get 'heat soak' issues easily on a warm day? (although I do live in the middle of Sydney, with lots of traffic and only have a SMIC)

Many thanks in advance for any help!

[h100vw]

It doesn't do anything on an AGU. I reckon as Australia got sent all the leftover AGU engines in mk4 GTIs after they stopped selling them in Europe. They ran out of SMICs without the hole, so had to fit MAP sensors to plug them.

*this might not be the whole truth

Gavin

[kendog]

haha, well, I definitely hope it's that simple..

So, if I were looking at a better FMIC, I could look at ones without a MAP sensor in the piping?

[h100vw]

Yep.

Gavin

[adammm]

Hang on

so if that is the 'map sensor' and its not plugged in with any of the AGU's in mk4 gti's, then why does my car still run without my Air Flow Meter plugged in ?

maybe im getting somewhat confused between MAF, MAP blah blah blah?

:|

[JustCruisn]

Hang on

so if that is the 'map sensor' and its not plugged in with any of the AGU's in mk4 gti's, then why does my car still run without my Air Flow Meter plugged in ?

maybe im getting somewhat confused between MAF, MAP blah blah blah?

:|

MAP <> MAF
MAF - Measures the mass of the air flowing into the engine. Located just after the air filter.
MAP - Manifold Absolute Pressure, measures the pressure in the system.

So techinlally only one or the other would really be needed. But AGU does not use the MAP on the IC.

If you have a look around you may also see a plug behind the driver side headlight that does exactly nothing also. I wonder if these 2 go together ?

[adammm]

So techinlally only one or the other would really be needed. But AGU does not use the MAP on the IC.
?

so in other words, our cars can run without the air flow meter plugged in?

[Stan]

so in other words, our cars can run without the air flow meter plugged in?

MAF is mass air flow, the plug immediately after the air filter, it in fact connects to its housing - car wont run well without that plugged in

[JustCruisn]

so in other words, our cars can run without the air flow meter plugged in?

No no. The engine managment is programmed to use the MAF. They could have designed it to use the MAP instead, with no MAF at all.
For the AGU VW probably choose MAF as it provides a more accurate reading, and therefore use less fuel. Some engines use both.

MAP Sensor VS. Maf Sensor | Tuning MAP sensors | Evo Maf

[adammm]

Sorry for the late replies, been having MAF sensor dramas :|

On another note, my car DEFINATELY runs without my MAF plugged in, will happily run on full throttle at 4.5psi, anymore and it spits the dummy!

AGU engine here aswell

[tmh983]

dragging out this old thread.

So can anyone answer the question that how does the ecu sense load if the maf is not plugged in?
My agu runs fine without the maf, boost is lower, but apart from that you would be hard pressed to notice a difference in responsiveness and general running of the engine. So it must have some method of sensing the load??? I can't find a map sensor anywhere on the manifold and there is no map pressure readout in VCDS, so it can't be using speed-density mapping, does this mean it simply uses throttle position as its only measure of load?

[Transporter]

No it doesn't have to. It just uses the back up program for this situation (when the sensor(s) fails).

[tmh983]

No it doesn't have to. It just uses the back up program for this situation (when the sensor(s) fails).

No it doesn't have to what? The ecu back up program still needs a method of sensing the engine load. It can't just guess at the correct injection and ignition timing...
Most other ecus i've seen run static injection timing on primary load sensor failure, this dictates that you can't run the engine under high load or rpm, it injects just enough fuel to keep the engine running and thats all, hence the term limp home mode. The agu ecu MUST have a method of calculatinginjection and ignition timing when the maf fails, and to do that, it must have a method of sensing engine load.

[aprr32]

How about throttle position V engine speed?

[tmh983]

throttle position mapping doesn't work too well in turbo cars because the air flow rate is not predictable enough. If u plant ur foot, initially there is no boost until the turbo responds, so the air flow is low, as the boost pressure rises, so does the airflow and therefore fuel requirement. but the throttle is still in the same position - so throttle position alone is not really enough information to accurately calculate fuel requirement (it can be made to work on non-turbo cars, but isn't used often as it is too sensitive to environmental changes ie. heat, humidity, changing the flow rate for a given throttle position).