A4 B5 naturally aspirated Throttle body and hoses clean up
 

OK, so I've had severe issues with my car, rough idle, car would lose power, it wouldn't keep the idle at all and shutdown, while driving the car would tend to accelerate by itself, etc.

So, after doing some real research and talking to my mechanic we performed the procedure explained below and it completely cleared all the issues and the only parts we replaced were the sparks just because I thought I would.
And, so I found a lot of information about this procedure for newer cars but nothing for the B5 naturally aspirate, everything out there is for the turbo versions, and I wanted to put it in pictures here for those who might find it useful. So in brief the whole process:

-Remove Throttle body, vacuum hoses and complete air intake and manifold.
-Clean everything from grease, oil and dirt.
-Clean MAF sensor and the air temperature sensor attached to the intake manifold
-Replace old o-rings from the throttle and injectors.
-Assemble everything back.
-Clear VAG codes that came from this procedure, perform TPS adaption, turn off and on the engine and test.

The steps:

-Start by removing the intake hose that comes from the air filter (I have the K&N cone filter so it will look different in the pic)

-Almost everything is attached by clamps, so you'll need a slotted screwdriver, the intake hose has 2 clamps, one in the middle and the other one attached to the throttle.

-Remove the accelerator pedal cable attached to the throttle body, removing it is like removing it from the brakes on a bike

-Disconnect as many hoses as you can from the throttle, again all clamped, just remember their location.
Be careful with the big ones on the back of the throttle as those are for coolant and you can create a big mess of water, use something to seal the hoses and stop the leak.

-Remove the 4 screws that are holding the throttle attached to the intake manifold, these are long screws and will come out with an allen type number 10 driver.

-You can now remove the throttle and the cave will look like this>


-At first we thought we'd check the PVC valve, also called bleeder valve in different models, but to our surprise we found that this car doesn't have any of these valves, instead it uses something called suction pump/vent pump and it seats on top of the intake manifold, it connects to the buster and to the vacuum lines, so you can clean its holes using carb cleaner, not the part that connects to the buster though. To my criteria it works as a PCV valve as well.


-Once the throttle is removed you can clean it carefully with carb cleaner and maybe a tooth brush, remove as much oil and grease as you can, careful not to leave any scraps, mine shined like brand new after cleaning, although the second pic below doesn't show it very well, but you can tell the difference:


-Now you can clean the intake hoses, the one that attached to the throttle was real dirty, the connections below it would almost not let any air in and out, carb cleaner did the trick here, also the oring was cranked:


-You can also do some cleaning on the intake manifold but only use a soft clothe, dont put carb cleaner in there or it will be very difficult to remove from the inside.

-Time to clean the MAF sensor and the air intake temperature sensor that is attached to the intake manifol, you know where the MAF is, use allen security screwdriver for the MAF and regular number 10 allen for the air temperature, use MAF cleaner, about 10 doses for complete oil removal. The difference is sight noticeable.


-During the process we noticed a leak of oil right below the intake manifold that was coming from one of the vacuum hoses, apparently the clamp wasn't properly tighten, of course we removed the hose and cleaned up everything with carb cleaner, one less leakage for the car :)


-Here is the whole thing with the intake completely removed


-Later that morning I wanted to see the physical state of the TPS (throttle position sensor right behind the throttle body), so we removed the allen screws and this is what it looked like:


It had some dust from the plastic gear normal friction, but it looked very good in general, you can see the 2 potentiometers that will tell the ECU the current opening angle of the throttle plate and the small motor that would automatically accelerate if needed, with all this system ready you'd think why this car doesn't have the cruise control, but hey it doesn't, such things in life...

-Well thats it, now re-build your engine's intake and make sure everything fits as is supposed to, tighten well all clamps and screws, put some new coolant liquid on your reservoir or water by default to replace the lost liquid. This is what it looks like on mine:


-And this is it with the air filter mounted:


-Finally we replaced the o-rings on every injector and mounted new iridium spark plugs.

-Now let the ECU get used to the assembly and detect any faults by just putting your car's key in the ignition position, don't turn it on at this stage, leave it there for a couple of minutes, you will hear the throttle, the fuel pump and maybe the coolant motor working for a while.

-Later on we started the engine just to make sure we re-assembled it right, it started with no problems, just had to push the accelerator a bit, immediately we noticed it would now maintain the idle but it was too high, at about 1200rpm. So we let it there for few minutes more before turning it off.

-We got the VAG-COM ready and at connection it threw about 10 different codes, all talking about the throttle, the camshaft sensor, the MAF low, etc.
Mech erased all those codes, did the throttle adaption via VAG and then let the ECU by itself.
Finally the ECU learned from its current state and threw no more codes at all. Yeii!! So yes, everything cleared up by erasing codes and doing the adaption.

We drove the car for a while and now idle was back to normal at around 9krpm, no more rough idle by the way, no more unexpected shutdowns from the engine, no more weird automatic accelerations while driving Everything perfect!

These are the tools I used:


By the way, during my research in forums and so some people were asking if the barometric sensor could be defective, this is supposed to be right next to the ECU in the ECU box which is to the right side of the water reservoir, but guess what, the blank space is there and in fact we found the part number and everything in ETKA but found out that this car just doesn't use the baro sensor as it is expected in the regular turbo version. This being naturally aspirated doesn't seem to need it. So don't look for it if you have the same engine as mine.

Anyway, hope you find it useful, although I'm not a mechanic neither a natural English speaker hence if you want to make me technical corrections please go ahead, I wanted to make it as clear as possible.
If anyone need part numbers I can give them to you, I just don't have them handy right now.

Merry almost Christmas!

Vacuum hose - where does it plug in ?
 

Hello,

Please excuse me if I am not posting correctly. I am new here.
I was looking at your post and I though you may be able to help me. I have an A4 1997 Quattro V6 2.6 naturally aspirated. There is a vacuum line that I have identified that is not connected currently to anything. It is in the location of one of the photographs that you have taken here, so I thought you may know where the loose end is supposed to terminate. In the picture it is attached to one part of the motor, and the other end that I have drawn the arrow toward is just dangling loose. I have a very rough idle. And looking around for vacuum leaks I found this hose. Its sucking air thru the open end that I have plugged with a nail for the time being. Which helped the idle. I am not a mechanic and do not know the terminology to well but do some of my own repairs. Just replaced the Ignition control module because it would not start. Now I'm trying to cure this very erratic idle.

Thanks,

Kumar

Nice writeup! I'll move this to the DIY subforum to keep it permanently close at hand.