Major vibration when idling

ANITA111

MEMBER
2009 AUDI A4
2.0L
4 CYL
TURBO
AUTOMATIC
98,000 MILES

I have been told that my car might only be running on 3 cylinders instead of 4 but without a diagnostics I won't know. The car seems to run great except when it is stationary then it judders quite bad almost like an old black cab, this is the best way I can describe it. Sometimes it's not too bad but then other times the whole front end of the car rattles.

5 Replies

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

It could be a misfire. By any chance, does the check engine light flash when you feel this? Also, does the check engine light stay on when the engine is running?

If it does, you need to have the computer scanned to identify diagnostic trouble codes related. Here is a quick video showing how it's done:

https://youtu.be/InIlnsjOVFA

I realize most people don't own a scanner. However, most parts stores will do it free of charge. This is where we need to start.

If possible, have that done, and let me know what codes are found.

I hope this helps. Let me know if you have other questions.

Take are and God Bless,

Joe

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Monday, February 22nd, 2021 AT 5:40 PM

ANITA111

MEMBER
3 POSTS

Hi Joe,

There is no warning lights on the dash at all. The ignition starts first time, I had this fixed last year at a cost of almost � 500. Unless it has been stood unused for a few days then it will take a few seconds longer to kick in. But definitely no warning lights at all.
Thanks, Anita

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Tuesday, February 23rd, 2021 AT 2:25 AM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Anita,

Do me a favor. When it is happening, pay attention to see if there is any black smoke from the exhaust or odd smells from it. Also, what was done last year that cost nearly $500.00?

Joe

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Tuesday, February 23rd, 2021 AT 2:29 PM

ANITA111

MEMBER
3 POSTS

Hi Joe,

Sorry that � 500 GBP I had the starter motor replaced. And definitely no smoke or smell from the exhaust.

Thanks, Anita

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Tuesday, February 23rd, 2021 AT 3:49 PM

JACOBANDNICKOLAS

MECHANIC
109,885 POSTS

Hi,

Since there is no check engine light or codes, then we need to start checking different things one at a time. Oftentimes, a rough idle is caused by engine vacuum leaks. A rubber vacuum hose could be damaged or removed, a gasket can be leaking, and so on. So, let's check for that first. Here is a link that explains how it's done. When following the procedure, avoid spraying around the exhaust manifold. If it very hot when running and the spray is flammable.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

I do have one other question. Does the check engine light turn on when you turn the key from off to the run position?

Try that and let me know what you find.

Joe