Cleaning FSI Throttle Body

I've decided to clean the throttle body on my FSI to prevent failure and have been following the excellent guide in the How To section.

It looks like this after 61k miles so definitely could do with a clean:



When cleaning however, is it safe to move the plate without risking damage to the actuator mechanism?

Also, are there any special precautions required to prevent the carb cleaner getting into the electronics on the side and causing damage? (e.g. clean it with the black plastic side upwards so the cleaner cannot run into the electronics?)
I've heard of a throttle body being broken during cleaning, although I don't know the procedure used - it could have been soaked!

warm regards

Andrew

ajsellors said:

I've decided to clean the throttle body on my FSI to prevent failure and have been following the excellent guide in the How To section.

It looks like this after 61k miles so definitely could do with a clean:

View attachment 14057

When cleaning however, is it safe to move the plate without risking damage to the actuator mechanism?

Also, are there any special precautions required to prevent the carb cleaner getting into the electronics on the side and causing damage? (e.g. clean it with the black plastic side upwards so the cleaner cannot run into the electronics?)
I've heard of a throttle body being broken during cleaning, although I don't know the procedure used - it could have been soaked!

warm regards

Andrew

Click to expand...

I cleaned mine by moving the throttle plate manually. It doesn't seem to have done any harm. It cleaned up nicely but I haven't noticed any difference.

Cheshire Cat said:

I cleaned mine by moving the throttle plate manually. It doesn't seem to have done any harm. It cleaned up nicely but I haven't noticed any difference.

Click to expand...

Thanks.

I cleaned it two nights ago and refitted last night. I left it in the house for 24 hours in the warmth so that the cleaner could evaporate if it had got somewhere it shouldn't be.

I found that I could not move the place on mine, at least it would not move with the force that I was willing to apply. That did make it a bit harder to clean but I used a stiff artist's size brush to remove the deposits on the edge of the plates and the small gap that was left between the plate and inside tube.

During cleaning I tried to keep the side with plastic panel where the actuator is on the top to reduce the likelihood of the cleaner getting in. I am happy to report that it still works!

I cleaned it mostly as a precaution to prevent future failure. I also changed the rear emissions (NOX) sensor and MAF at the same time and during last night's test drive the power delivery across the rev range was good and the hesitation which it was previously doing mid way has gone. The emissions sensor was previously throwing up an error code in the ECU and I changed the MAF because it was the original fitment and my experience is that they degrade in performance over time.

Cleaned throttle:



Sadly its not all good news, the test drive (and fault logs) reveal that the heat control flap is now stuck on full heating. I hope I haven't discovered where the A pillar window trim locking pin went....

regards

Andrew

By rear emissions sensor do you mean post cat? I am getting an intermittent loss of signal code for that one. It doesn't seem to affect performance though. How much is a replacement MAF? I don't think mine is faulty. I had one die on a BMW diesel and it made the car very lethargic.

Andy

Cheshire Cat said:

By rear emissions sensor do you mean post cat? I am getting an intermittent loss of signal code for that one. It doesn't seem to affect performance though. How much is a replacement MAF? I don't think mine is faulty. I had one die on a BMW diesel and it made the car very lethargic.

Andy

Click to expand...

Hi,

yes, the emissions sensor is post cat. If the ECU thinks a sensor isn't working properly it can cause it to revert to the default engine mapping rather than tune things to how the engine is actually performing. Although the engine will run fine, it would probably run better if everything was OK.
The emissions sensor was £139.74 + VAT from Audi. Its simple to change but access is a but awkward as its under the car. The wire runs under a plastic cover and into the front passenger foot well floor space where the control unit is. With anything attached to the exhaust, they don't always want to come off. I had to saw off the end of my old sensor and use a proper socket with a long bar to undo it.

The MAF sensor was £161.83 + VAT from Audi but you get a rebate if you return the old one as long as it is a genuine part as they recycle the tube part with a new sensor. I believe that's £45 + VAT back.

regards

Andrew

ajsellors said:

If the ECU thinks a sensor isn't working properly it can cause it to revert to the default engine mapping rather than tune things to how the engine is actually performing.

Click to expand...

That's rather for the pre-cat lambda probe... If the oxygen readings (before cat) are not reliable, than the injection is defined according to a map (depending on different parameters) instead of taking into account the remaining oxygen in the exhaust gases.
The post-cat probe has 2 functions : measure oxygen (like the other lambda) to detect a faulty cat, and measure NOx level to determine when a "regeneration" has to performed to empty the "NOx trap". If the sensor is malfuntionning on the latter readings, then the engine only works in stoechiometric mode instead of working also in the 2 lean burn modes (whic produce much more NOx).
So the performance will not be harmed, like you said. But fuel consumption won't be as good as it shoud.

fbi said:

That's rather for the pre-cat lambda probe... If the oxygen readings (before cat) are not reliable, than the injection is defined according to a map (depending on different parameters) instead of taking into account the remaining oxygen in the exhaust gases.
The post-cat probe has 2 functions : measure oxygen (like the other lambda) to detect a faulty cat, and measure NOx level to determine when a "regeneration" has to performed to empty the "NOx trap". If the sensor is malfuntionning on the latter readings, then the engine only works in stoechiometric mode instead of working also in the 2 lean burn modes (whic produce much more NOx).
So the performance will not be harmed, like you said. But fuel consumption won't be as good as it should.

Click to expand...

Thanks for that. Cruising fuel consumption on the motorway is good but other roads give less impressive mpg. Perhaps I'll have a look at the second sensor over the holidays.

The pre-cat sensor came off fairly easily. I've got a lambda socket which helped a lot.

If the MAF is failing does it throw up error codes? Nothing is appearing on VCDS.

Andy

I thought a malfunctionning MAF would throw up an error code. So does the NOx sensor. (be aware, it's approx twice the price of the pre-cat lambda probe)

fbi said:

I thought a malfunctionning MAF would throw up an error code. So does the NOx sensor. (be aware, it's approx twice the price of the pre-cat lambda probe)

Click to expand...

Hi,

the car was recording a fault on the NOx sensor. You could also tell something really wasn't right with the engine when driving it. It was sluggish (and my usual A2 is a 1.4 petrol) and there was a "flat spot" in the acceleration when going from low to high revs where the power appeared to dip.

As long as the MAF is doing something moderately sensible its difficult for the ECU to know whether its OK or not. It is possible to check if the readout of the MAF at idle is within an expected range of values but I haven't been able find out what that should be for the A2. My experience of MAFs in other cars is that over time they degrade with the reading drifting off true. After 4 years my Dad's A6 V6 TDI was hardly doing anything when pressing the accelerator. Changing the MAF restored the power. My TT's MAF was replaced after 6 years although in that case the effect didn't seem as great on the petrol engine as on the diesel. Given that the A2's MAF was the original (now approaching 9 years) I thought that as I was taking it off anyway to clean the throttle body I would treat the car to a new MAF.

After this the engine has been transformed. No flat spot and power is definitely up. On a two hour round trip to pick up a set of leather seats where I was treating the car to some brisk acceleration and fast motorway driving to give it a work out and make sure everything was OK. I was impressed at how it performed and the DIS reported an average of 40MPG even though I was trying to drive as uneconomically as possible!

regards

Andrew

Hmmm. I have a flat spot too. Perhaps I'll replace the MAF first. I was under the impression that failure was exclusive to the diesel engine although logically on reflection I can't see why. It's a bit easier to replace than the bottom sensor too.

Andy

ajsellors said:

Hi,

the car was recording a fault on the NOx sensor. You could also tell something really wasn't right with the engine when driving it. It was sluggish (and my usual A2 is a 1.4 petrol) and there was a "flat spot" in the acceleration when going from low to high revs where the power appeared to dip.

As long as the MAF is doing something moderately sensible its difficult for the ECU to know whether its OK or not. It is possible to check if the readout of the MAF at idle is within an expected range of values but I haven't been able find out what that should be for the A2. My experience of MAFs in other cars is that over time they degrade with the reading drifting off true. After 4 years my Dad's A6 V6 TDI was hardly doing anything when pressing the accelerator. Changing the MAF restored the power. My TT's MAF was replaced after 6 years although in that case the effect didn't seem as great on the petrol engine as on the diesel. Given that the A2's MAF was the original (now approaching 9 years) I thought that as I was taking it off anyway to clean the throttle body I would treat the car to a new MAF.

After this the engine has been transformed. No flat spot and power is definitely up. On a two hour round trip to pick up a set of leather seats where I was treating the car to some brisk acceleration and fast motorway driving to give it a work out and make sure everything was OK. I was impressed at how it performed and the DIS reported an average of 40MPG even though I was trying to drive as uneconomically as possible!

regards

Andrew

Click to expand...

I might try a MAF sensor replacement...
When my engine is cold (thus the ECU orders a richer air/fuel mix), it's always pulling way better than when hot.
My MAF may under-read the air flow ?

I'm back from a "long" trip to the French Alps ; my first long one in 6 years A2 motoring !! Before that, the A2 was OUR 3rd or 2nd car. Now it's MY main car. So I never went more than 200km far from Liege before...
Anyway, I was pleased with the fuel consumption, it was 6,5L/100km overall (43.5 MPG), what included motorways, B-roads, mountain roads...
First time ever that I managed to reach 700km (or even 600km) with one tank
But all the 110bhp were not along with me for the trip. It felt like I left at least 30 or 40 of them at home

The EML still comes on... The code scanner says the cat is below efficiency, the manifold flap doesn't reach its setpoint (and once a problem of communication with the aircon ECU ??)
The manifold flap problem can't be related to unaccurate MAF readings, but the O2 post-cat readings can be affected by this. The cat doesn't seem to be blocked ; at least the engine can reach the redline. Maybe mot "jump" to the redline, but not sure that the FSI is supposed to behave like this...

If the manifold flap isn't reaching the setpoint this sounds like the carbon deposits may be staring to stop them reaching the end of their travel properly and this is being picked up by the position sensor. The car in which I cleaned the throttle body that started this thread had the manifold replaced a year before I bought it for the same reason. I don't have the diagnosis, only the bill so the actuator plastic rod may have snapped as a result as the vacuum unit was replaced as well.

If the actuator is still OK in your car its possible to remove and clean the manifold out, although it's a much bigger job to take it off and put it back than when cleaning the throttle body.

regards

Andrew

I could try sea foam or similar cleaner in the intake air...

Is Sea Foam available somewhere in Europe (or is it possible to ship it from US)? Does it actually have other benefits compared to other carburetor cleaning sprays, than that U-shaped pipe/nozzle? It looks like a really cool feature, though I'm not sure how convenient would using it with A2 FSI be.

Here is my experience from today:
My A2's FSI has run about 133 000km and the problem was engine stalling rather easily (roundabouts, parking halls, ..) when not very careful. For long I thought it was a difficult/broken/worn clutch, but after reading stuff about this subject I decided to try throttle body cleaning. My plan first was to detach the throttle body and follow the PDF cleaning guide. However, when I saw throttle body MAF side was completely clean and remembered some horrible FSI head intake port/valve pictures I had seen, I decided it could be a better idea to inject my carburetor cleaning spray to the throttle body while the engine is running. This way it would have some change of cleaning also intake valves, etc. So, I reattached the MAF electric connector (and stored the MAF it a bit further!), got my dad to press gas pedal to prevent the car from stalling, and started spraying carburetor cleaner at the throttle flap.

I wouldn't recommend this method to anyone, but I had a spare-car at hand if something would have gone horribly wrong. Nothing bad seemed to happen, no flames from intake to my hands, no check engine lights (I don't have vag-com, so no idea about error codes). There should be some revs when doing this, because at idle throttle flap isn't really open and air flow is pretty modest. I should have shut down climate control before this operation (some spray vapors got sucked into the cabin unnecessarily). From exhaust came out some very black stuff and some liquid. I probably didn't inject even half of the spray bottle. No idea if I should have used more of this. A Sea Foam spray style U-shaped nozzle/pipe would have been awesome, as then MAF could have been connected still, and all spray would have gone into the engine. Now I was careful, and injected the stuff pretty far away. However, MAF being not on "air path" did not seem to cause any severe side-effects while doing this cleaning.

Now the engine does not seem to stall so easily when taking off at low revs! I am pretty amazed actually. Of course this could be just placebo, I wish so much I could measure this effect somehow. The engine also worked great on my last trip. DIS showed fuel consumption of about 4.8l/100km (on approximately a 50km drive, no air conditioning on, a warm engine to start with) which seemed very reasonable.