vibration when accelerating

Randy_31 · 03-19-2012, 06:13 PM

I have a 2009 P+ 6MT sport with 39M miles. I just started to notice that when I accelerate I get a vibration. The harder the acceleration the more vibration. Does not vibrate when coasting or not accelerating. I just got new summer tires put on about 500 miles ago, but would not expect to only happen when accelerating and I did not notice this until now. Its almost as if it is missing. No CEL showing. I do have a vagcom but I assume if there is no CEL it will not tell me anything, correct? Any ideas on what is going on before I take it into the shop?

snagitseven · 03-19-2012, 07:59 PM

Could be one of these (been there on all of these at some point in my life):

A rear tire wasn't balanced properly,
defective tire,
bent wheel,
lug nut(s) not torqued correctly,
drive train or rear suspension issue or
chassis or axle bolt loose;
doesn't sound like an engine issue.
Most likely one of the first three.

Randy_31 · 04-26-2012, 03:48 PM

Thought I would leave a follow up post on what the issue was. Eventually I ended up getting a CEL that indicated a misfire in cylinder 2. which turned out to be a bad injector. The dealer replaced all 4 while in there (still under warrenty) but seemed as if it was only the one. The dealer thinks it was probably defective. This also fixed the vibration issue. I noticed the vibrations before as I noted in my original post but did not realize how poorly the engine had been running in general. Guess it degraded slowly. With the new injectors there is a big difference in performance, especially starting from a stop.

jfo · 04-26-2012, 04:54 PM

Glad you got it sorted, and also under warranty. I'm no expert, but I believe a VagCom scan would have noted the misfires, even though it didn't set a CEL initially.

Randy_31 · 04-26-2012, 05:20 PM

I did run a scan before the CEL and did not show the misfire

av_audi · 04-26-2012, 05:31 PM

The frequency of injector problems seems to be non-trivial enough to be noticed.

Tagger150 · 05-01-2012, 03:46 AM

the fuel injector issue does seem to be a frequent issue.

See thread "EPC and CEL + power loss and shake".
http://forums.audiworld.com/showthread.php?t=2822230

av_audi · 05-01-2012, 11:24 AM

Quote:

Originally Posted by Tagger150

the fuel injector issue does seem to be a frequent issue.

I wonder whether there is something inherent to the injectors or whether the failures are caused by peripheral components such as a bad fuel filtering system, bad pressure regulator, etc. The failures could even be caused by fuel lines or fuel tanks degrading and dumping tiny particles into the fuel that damage the injectors.

03-19-2012, 07:59 PM	#2
snagitseven AudiWorld Super User 2013 Audi A6 Join Date: Jul 2001 Location: MA Posts: 3,990	Could be one of these (been there on all of these at some point in my life): A rear tire wasn't balanced properly, defective tire, bent wheel, lug nut(s) not torqued correctly, drive train or rear suspension issue or chassis or axle bolt loose; doesn't sound like an engine issue. Most likely one of the first three. __________________ - 2013 A6 3.0t Prestige, Quartz Gray/Black, 19" Sport, Driver Assist, LED headlights,Cold Weather and B&O; Bridgestone RE970AS tires; X-Pel Ultimate full front, mirrors and rocker panels - 2009 A4 3.2 Prestige w/Nav (sold at 48K mi) - 2002 allroad 2.7t - 48K mi after 12 years (and still like new) - 2001 A6 2.7t (sold at 98K mi)

04-26-2012, 04:54 PM	#4
jfo AudiWorld Member Garage is empty, add now Join Date: Nov 2010 Location: North of Whistler- British Columbia Posts: 113	Glad you got it sorted, and also under warranty. I'm no expert, but I believe a VagCom scan would have noted the misfires, even though it didn't set a CEL initially. __________________ Jim 2011 A4 Avant

05-01-2012, 03:46 AM	#7
Tagger150 Audiworld Junior Member Garage is empty, add now Join Date: Oct 2009 Location: Bethesda, MD Posts: 18	the fuel injector issue does seem to be a frequent issue. See thread "EPC and CEL + power loss and shake". http://forums.audiworld.com/showthread.php?t=2822230 __________________ Current: 2010 A4 Avant S Line, Driver Assist Quartz Gray/Black 2006 Range Rover HSE Black/Gray Previously Owned: 2003 Audi A4 Cabriolet 3.0 Black/Black

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04-26-2012, 03:48 PM	#3
Randy_31 Audiworld Junior Member Garage is empty, add now Join Date: Aug 2008 Posts: 26	Thought I would leave a follow up post on what the issue was. Eventually I ended up getting a CEL that indicated a misfire in cylinder 2. which turned out to be a bad injector. The dealer replaced all 4 while in there (still under warrenty) but seemed as if it was only the one. The dealer thinks it was probably defective. This also fixed the vibration issue. I noticed the vibrations before as I noted in my original post but did not realize how poorly the engine had been running in general. Guess it degraded slowly. With the new injectors there is a big difference in performance, especially starting from a stop.

04-26-2012, 05:20 PM	#5
Randy_31 Audiworld Junior Member Garage is empty, add now Join Date: Aug 2008 Posts: 26	I did run a scan before the CEL and did not show the misfire

04-26-2012, 05:31 PM	#6
av_audi AudiWorld Senior Member Garage is empty, add now Join Date: Apr 2000 Posts: 1,979	The frequency of injector problems seems to be non-trivial enough to be noticed.

05-01-2012, 11:24 AM
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