Hey guys. Besides my 99 Audi A4 1.8T, I also own a 2003 PT Cruiser Turbo with 31,000 miles on it. Even though my questions are concerning the PT Cruiser, I think it's a general situation that can possibly happen to my Audi. And more importantly, I know a lot of you guys are very mechanically inclined and I would really value your input on this.

About a week ago I noticed the PT was vibrating at idle (haven't noticed it when driving).

I took the car to the dealer yesterday and they recommended an engine decarbonization to remove carbon buildup and as a result of that procedure, the spark plugs would need to be replaced as well. Cost of repair: $464.

Or they also recommended a more complete tune up for $550. I told them I'd think about it and got my car out of there. The cost seems excesive to me and it doesn't look like they were sure that this would fix the problem.

My questions are:

1. Any idea what could be causing this vibration?
2. Has anyone gotten this engine decarbonization procedure done?
3. Would carbon buildup cause this type of vibration and if so, how?

I searched the forums for this topic but couldn't find anything that offered answers to my questions.
Thank you in advance guys for your help.

 

I think you may want to search for the word "seafoam". This is the stuff people put through their engines to remove buildup and crap. I personally have never used it though.

You can also try cleaning you MAF and Throttle Body... that worked for me.

 

yeah scroll down (might be on second page) thread about seafoam theres a link to a DIY to suck the stuff into the manifold... you can also dump it into your gas tank and into your oil a few miles before an oil change... I'm planning on doing it one day but I think you do need to replace some stuff after you do it... spark plugs? check it out... it was on here yesterday.

 

The service the dealer recomended should also include an oil change. The seafoam treatment would require the same. Ive seen the engine decarbs fix the problem you describe quite a few times.

 

Sea foam? OK. Let me research that.

In the meantime, it'd be great to hear from people who have used it to decarb the engine. Like if it's safe or if it would void the warranty in any way if something goes wrong, since my car is still under warranty.

Thanks again for the tip. I'm gonna go look it up.

 

Here is one good post I had bookmarked:

https://www.audiforums.com/m_174311/tm.htm