Jump to content

Welcome to RennTech.org Community, Guest

There are many great features available to you once you register at RennTech.org
You are free to view posts here, but you must log in to reply to existing posts, or to start your own new topic. Like most online communities, there are costs involved to maintain a site like this - so we encourage our members to donate. All donations go to the costs operating and maintaining this site. We prefer that guests take part in our community and we offer a lot in return to those willing to join our corner of the Porsche world. This site is 99 percent member supported (less than 1 percent comes from advertising) - so please consider an annual donation to keep this site running.

Here are some of the features available - once you register at RennTech.org

  • View Classified Ads
  • DIY Tutorials
  • Porsche TSB Listings (limited)
  • VIN Decoder
  • Special Offers
  • OBD II P-Codes
  • Paint Codes
  • Registry
  • Videos System
  • View Reviews
  • and get rid of this welcome message

It takes just a few minutes to register, and it's FREE

Contributing Members also get these additional benefits:
(you become a Contributing Member by donating money to the operation of this site)

  • No ads - advertisements are removed
  • Access the Contributors Only Forum
  • Contributing Members Only Downloads
  • Send attachments with PMs
  • All image/file storage limits are substantially increased for all Contributing Members
  • Option Codes Lookup
  • VIN Option Lookups (limited)

RPM Dip at Idle on '05 CS


Recommended Posts

I have a phenomenon that occurs under all conditions but is worse when cold on my 2005 CS.When coming to a stop at a speed faster than a crawl, the engine RPMs dip to 400 rpm on the tach and then recovers back to normal speed of about 500.I can hear the engine lug down a bit when it hits 400 but quickly recovers.This issue occurred a few years ago but was "fixed" at the dealer by cleaning the throttle plate.Before digging into the intake, I wanted to see if there was a definitive fix to this issue.Anybody else seen this?

Link to comment
Share on other sites

Thanks Loren! I'm not sure if this is the case but i will check the DME fault codes and see if anything is stored.

The TSB is not crystal clear but it seems the MAFs may not be outputting proper voltage and cause rough idle. This would explain why it would exhibit rough idle on fairly stiff off-throttle and not from a crawl.

Edited by Scott C
Link to comment
Share on other sites

Hi. As i know its a very common issue inside the cayenne community. I had / have the same.

The drop of rpm is a secret issue for me.

We have 2 cayenne s. One has this issue again and again, the other car never had it. This is a miracle for me. We changed coils and plugs, filters. New MAF's and finally in the last weeks a new throttle body. And what you think?! The idle dropping story still continues. So all what i can say, cleaning the throttle body can help you but as you can see in my case, even a new part didnt solve the problem.

Link to comment
Share on other sites

Thanks for sharing your experience. It is not re-assuring that the issue is not easily identified.

I will follow with TSB and see if 1.1V is present so I can rule out MAF.

The throttle plate cleaning appeared to help in my situation in the past so I may pursue that route.

The only other thing I can imagine is a vacuum leak causing this to occur...... Especially when cold.

Good luck!

Link to comment
Share on other sites

I went already to porsche explaining the problem but looks like here in the forum guys have more knowledge about this car than all this so called specialists. Last story: i asked to change fuel pump and fuel filter. Answer from shop: cayenne dont have a fuel filter. So far about know how of porsche specialists:-(

Link to comment
Share on other sites

Thanks for sharing your experience. It is not re-assuring that the issue is not easily identified.

I will follow with TSB and see if 1.1V is present so I can rule out MAF.

The throttle plate cleaning appeared to help in my situation in the past so I may pursue that route.

The only other thing I can imagine is a vacuum leak causing this to occur...... Especially when cold.

Good luck!

Oh wonder oh wonder, the problem is solved!

What i can say, i had the truck in the shop to replace the fuel pumps. Not because of this idle problem but because of some strange behaviour during full speed driving.

And guess what, THE IDLE DIP PROBLEM IS GONE!!! I am so happy.

What i learned from this, idle dip problems could be caused by fuel pressure problems.

Merry Xmas

Link to comment
Share on other sites

You may be onto something here. Recently the rear fuel pump has started whining rather loudly where it didn't do this in the past.

Certainly fuel pressure has an affect on idle.

I'll look into this and see if the connections are loose like yours.

Link to comment
Share on other sites

You may be onto something here. Recently the rear fuel pump has started whining rather loudly where it didn't do this in the past. Certainly fuel pressure has an affect on idle. I'll look into this and see if the connections are loose like yours.

Was the same with me. Right side noisy . They changed this one and found out, that the main pump on the left was not working.Noise come From right one just because thisOne had to work much more. My advice, check all cable connections or if neccessary change pumps.Dont do it by yourself please.
Link to comment
Share on other sites

  • 7 years later...
On 12/19/2012 at 2:04 AM, ekstroemtj said:

Hi. As i know its a very common issue inside the cayenne community. I had / have the same.

The drop of rpm is a secret issue for me.

We have 2 cayenne s. One has this issue again and again, the other car never had it. This is a miracle for me. We changed coils and plugs, filters. New MAF's and finally in the last weeks a new throttle body. And what you think?! The idle dropping story still continues. So all what i can say, cleaning the throttle body can help you but as you can see in my case, even a new part didnt solve the problem.

 

Hello,

 

Have you found the issue for the drop rpm issue? I have changed everything can think about but still with low rpm stall.  Thanks,

Link to comment
Share on other sites

9 minutes ago, ekstroemtj said:

You have changed both pumps?

Yes both fuel pumps have changed!  The vehicle start in cold no problem and no hesitation, only when in warm up then the RPM drops much like low to 440 and then stalls eventually. 

Edited by paulwu
Link to comment
Share on other sites

I am not a professional but o guess there is a leak somewhere. Many times with higher temperatures it feels more  and more. To find a leak is difficult. But before hunting for leak take a look at the MAF . If possible Clean them

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.