Audi A6C5 1.8t - Wavy revs after firing, sudden drop in revs after braking

Question

Hello, my problem is described on various forums but so far I have not found a solution. Namely, I have an audi a6c5 1.8 t. Multitronic, for some time I have been struggling with the problem of undulating revolutions after firing, idling and a sudden drop in revs after decelerating the car to 0.

mkubol · Answer

First of all, all leaks at the inlet and before and after the turbo. Check the vacuum pump, oil level in the box.

Daniel198632 · Answer

Hoses checked, chest after regeneration, throttle replaced, flow meter, head after regeneration, new temperature sensors, stop sensor ... hands and wallet are falling

mkubol · Answer

Replaced the throttle and the adaptation carried out? Vacuum pump? Hard brake pedal? Haven't you felt less braking? And when did this fault occur?
After regeneration of the box or head. Were all these repairs due to the rippling turnover. Little data, you would have to describe everything in turn with photographic documentation what was done and why, including the dynamic test on the computer.

Daniel198632 · Answer

This sudden drop in revs when decelerating the car accompanies me from buying this car, the gearbox was regenerated due to jerking when starting. The head was completely regenerated after it turned out that the gasket was gone. All these activities did not eliminate the drop in RPM, the new throttle, of course, with the adaptation and the flow. With smooth braking, the revs drop as they should, it is also strange that this happens in the first phase of the journey, about 20 km. I will try to provide more data but I cannot access the computer.

mkubol · Answer

I propose to check all vacuum hoses and their seals, the invisible cracks of such hoses are quite common. There was also a hardened servo seal several times. Vacuum tank, check valve and all solenoid valves together with the end actuators. The boost is vacuum-controlled and probably the EGR valve and that should be looked at too. It may close with a delay or let it pass, and for diagnostic purposes it may be blinded.

Daniel198632 · Answer

Thanks very much, I will check everything and I will write what the effect was.

Daniel198632 · Answer

Maybe you have information on some overwhelmed mechanic near Poznań?

mkubol · Answer

Inowrocław #http: //brk-tuning.pl# if it's not too far.

Daniel198632 · Answer

Hello, and I come back to the topic again. Vacuum checked, pneumothorax clean, the alternator after regeneration because the charging was already quite low and the revolutions still drop when braking. There was also the domain of oil for the box and no reaction so it's probably not a box.

mkubol · Answer

Buddy, please check the vacuum pump with a pressure gauge or other device measuring the vacuum. Up to 100 miles Bar, the pump is functional, after the above something wrong with the pump or (if you connect to the entire system and not the pump itself) leakage on the vacuum hoses.

Daniel198632 · Answer

Okay, I'll check it out myself. Thanks for the tips.

mkubol · Answer

I also suggest checking the vacuum accumulator (such a tank connected to the vacuum system). It eliminates sudden fluctuations in the system. To make a test :
-Engine is idling
- vacuum pressure gauge connected to the entire system
-pump with the brake and watch the pressure gauge

Vacuum drops above 300 milliBar are the faulty battery and clogged kinked hoses leading to it.
There are still check valves worth checking out.

Daniel198632 · Answer

Thank you very much for your support, although the mechanic told me something like that, and I quote ... We measure the vacuum pressure with a vacuum gauge, then petrol pump vacu is not here (it's not diesel) the vacuum is sucked from the collector vacuum drop to such an extent would reveal a problem with the brake. The problem is in a certain temperature range, the loss of vacuum, whether hot or cold would be the same.

mkubol · Answer

Everything is correct, gas pumps do not have a vacuum pump, but slow suction pumps, they do! , the drop in the vacuum may affect the undulating rotation and not necessarily the brake to that degree. A brake problem is a hard brake pedal and a lot more force to brake.
As he snobie would call a vacuum gauge his case.
I suggest asking the mechanic to show where in the intake manifold (in the turbine engine) is the vacuum used by the servo and other components.

Daniel198632 · Answer

After plugging in the simplest tester, such an error appeared

mkubol · Answer

As I wrote before! Accurate diagnostics of the vacuum system, including servo. Link

Daniel198632 · Answer

I would have a friend far from you

mkubol · Answer

Probably yes. Germany near Frankfurt am Main But you just need to visit a normal mechanic who, although he knows that turbo-charged cars have a vacuum pump.

Audi A6C5 1.8t - Wavy revs after firing, sudden drop in revs after braking

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