Engine hesitations

4.2 V8 32v Naturally Aspirated - 414 bhp
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dump
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Engine hesitations

Post by dump » Fri Mar 31, 2023 12:24 am

Hello guys,

My Rs4 b7 makes me crazy :cry:

For several months, she has engine hesitations between 2000 to 3000 rpm as soon as the engine start eating. Before 50°C, it runs perfectly. No hesitation, engine revs perfectly from 0 to 8000rpm+

When the engine is at 90°C, I can feel hesitation. Sound exhaust is also changing with strange high sound noise like a whistle :roll:

Car smell gasoline at the exhaust, she seems to run rich, black smoke sometimes at high rpm

https://youtu.be/dyxVM08fRzU

After 3500rpm, she’s running perfectly until 8250rpm.

Here is what I already changed:

Spark plugs x8
Ignition coils x8
Lambda sensor x2 (before kat)
Mass airflow sensor
Carbon cleaning
PCV valve
Air filter
Gasoline filter

-Zero defaults on the VCDS
-No misfire even by driving between 2/3000rpm when hesitations are there.
-Flaps are still there and working well, no game, they move easily. No chip tuning, no modification.
-Fuel pressure seems to be ok

Pleaaaaaase Heeeeelp, I’m lost… :(

dan32v
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Re: Engine hesitations

Post by dan32v » Fri Mar 31, 2023 11:31 am

dump wrote:
Fri Mar 31, 2023 12:24 am
....with strange high sound noise like a whistle :roll:
Be careful, sometimes it is the membrane of the oil separator (or PVC) that is pierced...

dump
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Re: Engine hesitations

Post by dump » Fri Mar 31, 2023 11:51 am

dan32v wrote:
Fri Mar 31, 2023 11:31 am
dump wrote:
Fri Mar 31, 2023 12:24 am
....with strange high sound noise like a whistle :roll:
Be careful, sometimes it is the membrane of the oil separator (or PVC) that is pierced...
I know, but the sound is coming from the left exhaust, no noise close to the engine

dan32v
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Re: Engine hesitations

Post by dan32v » Sat Apr 01, 2023 9:53 am

Exhaust manifold leak ? :cry:

dump
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Re: Engine hesitations

Post by dump » Sat Apr 01, 2023 2:20 pm

Nope, hissing is coming from the muffler

Check my video on my first message :wink:

My first idea was injectors, but unfortunately there is no way to test them even with the VCDS. I don’t want to disassemble them and spend 1.5k€ for nothing

dan32v
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Re: Engine hesitations

Post by dan32v » Sun Apr 02, 2023 10:36 am

OK.

I think it turns like a potato. :bash:

It sounds like a valve leak... :bowdown:

dump
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Re: Engine hesitations

Post by dump » Sun Apr 02, 2023 11:07 pm

I know…

Engine is running perfectly until it starting to heat.

It’s worst when outside temperature are high.

I did a diag with my VCDS yesterday, and still no fault code :bash:

dan32v
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Re: Engine hesitations

Post by dan32v » Mon Apr 03, 2023 9:52 am

Indeed, it will not be easy to find the cause or the faulty sensor without a defect report except a stroke

of luck...

In any case, there is a sensor that changes state or gives wrong information depending on the

temperature. :x

dan32v
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Re: Engine hesitations

Post by dan32v » Mon Apr 03, 2023 10:07 am

:?:

Variable Valve Timing Failure – Audi 4.2 V8

Audi’s V8 engines use variable valve timing technology, commonly referred to as VVT or Vanos. The system variable alters the position of the camshaft, allowing for more precise intake and exhaust valve timing.

The system uses a VVT Solenoid which is actuated via oil pressures to control the camshaft timing. These solenoids frequently get clogged or gunked up which can cause them to fail and lead to performance and timing related engine issues.

https://www.ecstuning.com/b-genuine-vol ... utm_term=1


Image

dump
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Re: Engine hesitations

Post by dump » Wed Apr 05, 2023 9:53 pm

dan32v wrote:
Mon Apr 03, 2023 9:52 am
Indeed, it will not be easy to find the cause or the faulty sensor without a defect report except a stroke

of luck...

In any case, there is a sensor that changes state or gives wrong information depending on the

temperature. :x
That’s true and I know that it will be not easy to find which one… :bash:

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