Hey there again.

Info:
-6n2 Polo
-AHW Engine (1.4L 16v)
-Automatic transmission

Problems:
-Very slowly accelerates towards 1500rpm.
-Everytime I press or release the brake it goes to 2200+ rpm.
-Everytime I change gears (R or D) the car kinda "hits".

 

Story/What I have done:

Part 1.
Ok so at home there is this 6n2 Polo since 2002. Everything was fine until 10+ years ago when it started to show a problem: the transmission would hit hard every time you changed gears (as seen in this video: https://youtu.be/Xvj2W9wDnS4). We called a mechanic but he didn't solve the problem. For that reason, the car was "abandoned" and remained stopped until a year ago when we started fixing the car by ourselves.

 

Part 2: The return to the proyect.
Recently, we decided that we will fix the car again. Short story, we changed the oil, the oil filter, the fuel pump and the fuel filter. We put in some coolant and started the car. We had to put in some steering fluid because the car was making noises when you turned the steering wheel (the steering fluid solved that problem).

 

The car started, but there was one problem: It would start at 1100+ rpm and gradually rise the rpm until it got up to 2200 - 2500rpm. We did research and cleaned the throttle body with carb cleaner, that solved nothing. Did some more research and disconnected the MAP sensor. The car started at a lower rpm but still increase quickly over time (so it didn't solve the problem). 

 

From the beginning I suspected that there is a vaccum leak, for that reason we started looking for it. We found a thick hose connected to a black circular tank (brake booster / brake servo I think) that was deteriorated. For that reason we replaced the hose with another one (not oem, but similar in diameter and installed it with some hose clamps). That solved part of the problem, we started the car and now it won't rise to 2500rpm, but to 1500rpm. Then, we found a hose connected to the fuel pressure regulator that was disconnected and deteriorated at the other end. We replaced it with and connected it in both ends (I asked where to connect it in this same forum days ago). We started the car and it started at 800rpm but still very slowly rises up to 1500rpm, as seen in this video: (https://youtu.be/MzpoO_Gt2q8). Once it got to 1500rpm it would very slowly go back and foward with the rpm, as shown in this video (I had not noticed it until I watched the video at 10x the speed): (https://youtu.be/a--R1xSziKk). Other problem that we noticed is that when we press or release the brake pedal, the car revs up to 2200rpm for a very short period, also the car changes rpm as you move the steering wheel.

 

So recapping: 
-The (automatic) transmission of the car "hits" every gear change (https://youtu.be/Xvj2W9wDnS4)
-The car starts at 800rpm and very slowly rises up to 1500rpm (https://youtu.be/MzpoO_Gt2q8)
-At 1500rpm, the car would very slowly go back and foward with the rpm (https://youtu.be/a--R1xSziKk)
-Finally, when you press or release the brake pedal, the car revs up to 2200rpm for a very short period.

 

Extra: Engine sound (https://youtu.be/UM4zdmN2EX0)

Help.

Edited 27 October, 20205 yr by fganthony16
Links fix

Update: I lifted the front part of the car and there is a lot of grease/oil under the car, what do you think about it?

Also you can reply with any of your theories, it would help a lot.

Edited 28 October, 20205 yr by fganthony16

I'm afraid I haven't had heaps of experience with automatic transmissions having only owned a Volvo 240 with one years ago but I have to say that 'thump' when you put it into D seems rather violent! Again, no experience with polo auto units but that seems to me like the torque converter is to blame. Worth checking the engine and transmission mounts as well - it looks like something is moving with enough force to visibly make the car lurch. The noise could be the transmission whacking against its mounts perhaps? My hunch would be a knackered torque converter not allowing a smooth enough transmission of crankshaft torque to the gearbox and the whole unit lurches as a response. I can imagine the same thing happening with degraded mounts on a manual unit and raising the clutch quickly.

 

Can't see the image above but oil only comes out of a leak - either placing a load of cardboard under the car to see where the leak 'paints' or degreasing and cleaning and seeing where is oily afterwards will help you find where the leaks are coming from.

 

As for the engine speed behaviour I can't help much as I've only got a mk2f myself.

With most Autoboxes, if the oil level is too low you will get all sorts of problems and these can also have an effect on the engine performance as well, so I would start by draining the gearbox and replace the filter pack inside the gearbox, then refill with the correct grade and quantity of ATF fluid