RPM flactuates on cold start ups, hissing sound (with video)
04-08-2014, 07:52 AM
#1
AudiWorld Newcomer
Thread Starter
Join Date: Apr 2014
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
RPM flactuates on cold start ups, hissing sound (with video)
Hi guys,
I have a 2006 Audi A6 2.4 v6. Every morning when I start my car the rpm fluctuates. It usually happens for about 5 mins and after the engine is hot, it goes away. When the rpm drops, the speedometer lights will also get dimmer. I opened the bonnet and I noticed that there is a hissing sound (i am not sure how to describe it, but pls refer this youtube video). The RPM drops when the sound can be heard. I initially thought it was a vacuum leak, but my mechanic checked and he said there is no leak. There is also no error codes. My mechanic is stumped, and so am I! I was thinking it could be the MAF, but if it were, there should be an error message rite?? Thanks in advanced
YOUTUBE VIDEO
I have a 2006 Audi A6 2.4 v6. Every morning when I start my car the rpm fluctuates. It usually happens for about 5 mins and after the engine is hot, it goes away. When the rpm drops, the speedometer lights will also get dimmer. I opened the bonnet and I noticed that there is a hissing sound (i am not sure how to describe it, but pls refer this youtube video). The RPM drops when the sound can be heard. I initially thought it was a vacuum leak, but my mechanic checked and he said there is no leak. There is also no error codes. My mechanic is stumped, and so am I! I was thinking it could be the MAF, but if it were, there should be an error message rite?? Thanks in advanced
YOUTUBE VIDEO
04-08-2014, 10:10 AM
#3
Audiworld Junior Member
Join Date: Apr 2011
Posts: 84
Likes: 0
Received 0 Likes
on
0 Posts
Hi guys,
I have a 2006 Audi A6 2.4 v6. Every morning when I start my car the rpm fluctuates. It usually happens for about 5 mins and after the engine is hot, it goes away. When the rpm drops, the speedometer lights will also get dimmer. I opened the bonnet and I noticed that there is a hissing sound (i am not sure how to describe it, but pls refer this youtube video). The RPM drops when the sound can be heard. I initially thought it was a vacuum leak, but my mechanic checked and he said there is no leak. There is also no error codes. My mechanic is stumped, and so am I! I was thinking it could be the MAF, but if it were, there should be an error message rite?? Thanks in advanced
YOUTUBE VIDEO
I have a 2006 Audi A6 2.4 v6. Every morning when I start my car the rpm fluctuates. It usually happens for about 5 mins and after the engine is hot, it goes away. When the rpm drops, the speedometer lights will also get dimmer. I opened the bonnet and I noticed that there is a hissing sound (i am not sure how to describe it, but pls refer this youtube video). The RPM drops when the sound can be heard. I initially thought it was a vacuum leak, but my mechanic checked and he said there is no leak. There is also no error codes. My mechanic is stumped, and so am I! I was thinking it could be the MAF, but if it were, there should be an error message rite?? Thanks in advanced
YOUTUBE VIDEO
could not just guess what is going on in there, have it scanned with VCDS
04-08-2014, 03:25 PM
#4
AudiWorld Super User
Are you sure that the mechanic really checked all of the vacuum lines? I have a 2005 4.2 and it is my understanding that you need to remove the manifold to get to some of the vacuum lines. I had the hissing noise you described a few months ago and after removing the manifold determined that it was one of the vacuum lines. After replacing the vacuum lines the hiss noise went away.
04-09-2014, 07:22 AM
#6
AudiWorld Newcomer
Thread Starter
Join Date: Apr 2014
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
i actually changed the intake manifold 2 months back. i will ask him to check tomorrow. Tq According to my mechanic, he suspects that it has something to do with a sensor.
According to my mechanic, he suspects that it has something to do with a sensor.Are you sure that the mechanic really checked all of the vacuum lines? I have a 2005 4.2 and it is my understanding that you need to remove the manifold to get to some of the vacuum lines. I had the hissing noise you described a few months ago and after removing the manifold determined that it was one of the vacuum lines. After replacing the vacuum lines the hiss noise went away.
04-09-2014, 08:26 AM
#7
But agree with Kevin that vacuum leaks are pretty common and a relatively easy fix. Do a smoke test if unsure and you will find the culprit. Also, that engine seems to be 'ticking' quite a bit...
Trending Topics
04-10-2014, 06:05 PM
#8
AudiWorld Newcomer
Thread Starter
Join Date: Apr 2014
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
no the engine is no ticking. the video makes it sounds worse than it really is. also it was a cold start, once it warmed up, the sound is reduced.
back to the hissing sound, my mechanic has checked all of the hoses, and there is no leak. its a real pain to diagnose as it only happens during cold start.
back to the hissing sound, my mechanic has checked all of the hoses, and there is no leak. its a real pain to diagnose as it only happens during cold start.
04-10-2014, 06:06 PM
#9
AudiWorld Newcomer
Thread Starter
Join Date: Apr 2014
Posts: 6
Likes: 0
Received 0 Likes
on
0 Posts
btw what is a smoking test?
no the engine is no ticking. the video makes it sounds worse than it really is. also it was a cold start, once it warmed up, the sound is reduced.
back to the hissing sound, my mechanic has checked all of the hoses, and there is no leak. its a real pain to diagnose as it only happens during cold start.
back to the hissing sound, my mechanic has checked all of the hoses, and there is no leak. its a real pain to diagnose as it only happens during cold start.