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)
ALEV8

Weird starting idle drop and difficulties AGAIN

Recommended Posts

I have now changed everything but starter, injectors and motor mounts. You name it, I've replaced it. Vacuum lines, plugs/coils, the entire fuel delivery system.....and we are back to square one of start the car, if it starts on the first try, and there's a massive RPM drop immediately after the engine busts off like the thing is going to die, accompanied by a huge shiver of the motor, then smoothing out of idle. Replacing my torque arm mount initially mitigated this, and each subsequent ignition change really helped. But, just in time for Halloween, the ghost has returned.

Now what? The only thing I can think of is break down and buy a Durametric and laptop and start looking for more vacuum leaks at the intakes and throttle body, etc......so frustrating. My mechanic is saying I need a new starter. He also seems to only want 8+ hour jobs from me......bad sign.

Edited by ALEV8

Share this post


Link to post
Share on other sites
    You can remove these ads by becoming a Contributing Member.

It would have seemed prudent to buy the Durametic before purchasing what was undoubtably hundreds of dollars of parts..  Just a thought. Diagnostics usually saves money in the long run over throwing parts at a problem.  And your mechanic sounds like someone to keep the P!G away from. Look for a new mechanic.

Edited by deilenberger

Share this post


Link to post
Share on other sites

Hey man! Certainly would have but that's no fun. I wouldn't rebuild my Carrera 4 '89 chassis back into a usable state (bought it w/o engine) if I wasn't willing to spend money and fiddle with things. it's more a function of having a reliable mechanic become unreliable. I need to get back to my BMW days and self-diagnose more, Hence purchasing a high-quality diagnostic tool. regardless, I felt I had gone in the right direction and the feel of the vehicle was positive, now I'm not so much.

I'm still voting for vacuum leaks.

Edited by ALEV8

Share this post


Link to post
Share on other sites

Realistically everything you've replaced probably should be replaced with the age of your CTT. My experience on my first CTT (03 new to over 175K Miles) was that issues like you are describing are often caused by several issues that are occurring concurrently. Really the only way to accurately diagnose in my case was using a Durametric tool and the latest software. Also, do yourself a favor and replace the motor mounts. In my local club I haven't seen one 03, 04 or 05 that didn't need new ones. Also your starter is probably a couple months from starting to sound like a kazoo, don't forget the transmission mount as well.

 

Good on you on the 89 rebuild. 

 

Cheers! 

Edited by Pkscheldt

Share this post


Link to post
Share on other sites

First thing I would do, are motor mounts. They are hydraulic and they collapse with age.

Share this post


Link to post
Share on other sites

For sure mounts are next but my understanding is that the process is lengthy and onerous.

Share this post


Link to post
Share on other sites

It is, but It most likely is causing the idle drop. It did on mine as a matter of fact every rubber bushing on your PIG is suspect.

Share this post


Link to post
Share on other sites

I wish this was something I could tackle as I have access to everything via a friend's shop. Is there a TSB or Porsche guide here for engine or tranny mounts? I've downloaded all I find relevant. The subframe must drop and engine raise to replace the mounts....the idle drop while coming to a stop is one thing but at startup?

Share this post


Link to post
Share on other sites

The engine must be removed on the Cayenne Turbo (M48/50) → 100119 Removing and installing V8 4.5 l engine - section on "Removing". The turbochargers are removed next. → 213021 Removing turbocharger - section on "Removing" [9PAAF1 9PAAJ1]→ 213021 21 Removing turbocharger - section on

"Removing" [9PAAE1 9PAAE7

Share this post


Link to post
Share on other sites

It's unfortunate that the issues we live with on these cars don't always line up with easy cheap fixes.... I pulled the invoice on mine, I paid 7 hours to have the mounts replaced and then a bit more to have the 02 sensors replaced while they were at it. It worked in my case. The ultimate fix for all the wonky issues I was having though with my aged CTT was replacing it with a new one.

 

Cheers!

Share this post


Link to post
Share on other sites

I do not share your sentiments regarding replacement. Why spend way more money when all I would likely buy is a CTTS later production date. Far cheaper to be happy with what I have and fix as necessary. Two project cars and two drivers are enough. Being able to do it myself is fun and if it's near impossible without serious intervention, well that's zero fun! I do want that durametric though.

I do love the 2010 CTTS just not worth spending on it now with a toddler in private school, etc. What for? I love this car, and it's fast as hell plus looks great. I can and have hunted from it and wheeled it.

Edited by ALEV8

Share this post


Link to post
Share on other sites

I agree on the 2010 CTT, I purchased a 2013 CTT much better lines etc. for my taste.

I purchased my 2003 CTT new and loved it for over 10 years, but lived with many issues and completed dozens of DIY projects some of which were electronic and were never resolved even after module replacements re-flashes etc.

I'll add this though, you are posting on this forum asking for help/suggestions, some of the resolution you are and will be seeking on your CTT will prove to be insanely expensive, but that's part of your journey. Do yourself a huge favor and buy the Durametric asap, It will help you with nearly all of the issues you've played though including your fuel pumps, idle etc.

Edited by Pkscheldt

Share this post


Link to post
Share on other sites

Can someone explain how a failed engine mount can cause an idle issue/surge? Have you smoke tested the system for leaks? Throttle body issue?

Share this post


Link to post
Share on other sites

Supposedly was smoke tested and I am getting the durametric asap. See above comment by Wv as I'm seeking to understand not just repair. These are tough 4x4s and should be in service well past 125k mi as I have on mine. Just want a bit nicer idle.

Share this post


Link to post
Share on other sites

If you had the Duramteric or PIWIS you could pull codes for the throttle body and values for the MAFs.  All of which need a good cleaning if they haven't been at 125K. 

 

It is well documented (read through many posts here and with the VW's) that bad motor mounts/transmission mount on Gen I V8's have caused rough idle. They did on mine, PNA is who recommended the fix. I went through everything from fuel pump, new throttle body (I have an extra if you'd like it) MAF's, fuel system, to all vacuum lines, plugs and coils (6 total set for 175K miles)  At 140K all mounts including the transmission mount had completely failed, they were between 15 and 20mm shorter than the replacements on mine. The 02 sensors being replaced helped a bit as well. If you reference an early comment of mine I mentioned that often my issues with the 03 CTT were caused by a few issues happening at the same time. But to find any logic in the cause of the many of the issues I had was a fools errand... Examples: explain why an extremely minor volt drop in the battery on my previous cayenne could cause a PSM failure warning and shut down the air suspension and put the car in limp mode or a can bus system failure or randomly the nav and head unit, but they did for me and for many others. The fact is while the Gen I is a great car and is physically tough, it's wonky as hell when it comes to "electronic" issues such as idle PSM and eventual can bus issues. The Durametric tool was invaluable for clearing these random codes providing a reset. Go to your local P dealer walk into service and have a chat with a tech, they'll tell you, they'll also tell you they've worked through most of the issues in the subsequent gen's. I found that I loved the 03 enough to overlook some of these quirks. When I started running into multi thousand dollar repairs the last year I bailed. Do a quick search on this forum for  "2003 Cayenne Turbo Won't Start" and you'll see the reason she and I parted ways. Back when that happened folks such as Wv suggested that I replace the battery, which by the way should always be where you start, unfortunately it ended up being a little more involved in my pocket book.... Right before that I replaced the Trans valve box and control module  - that was actually a fun project but a little pricey.

 

Cheers!

Edited by Pkscheldt
  • Upvote 1

Share this post


Link to post
Share on other sites

Understood! Durametric will be enroute. I'll also order the mounts. If my fixes start running into quad-zero range I'll consider another vehicle to be certain. I'm fantasizing that the C4 964 will suffice. I'll add that as a stay at home dad I'm not a commuter and thankfully don't live in the car. I don't want to get stuck somewhere either! The durametric should have happened long ago. I have never touched my MAFs or TB ever!

Share this post


Link to post
Share on other sites

Mounts will not cause a rough idle, only transmit engine harmonics to chassis when the mounts collapse and they will not cause a idle surge condition. Mounts can sometimes cause separation of air intake plumbing and such if they allow too much engine movement under load. I just think there should be a proper clarification in description of the symptoms and the solutions.

Share this post


Link to post
Share on other sites

Ok, was at the P shop yesterday for service on the new CTT and the Master tech was working on my car. This is what he told me re this issue and I hope it helps:

 

There are many reason's why the first gen CTT has a rough idle in general, and then as the vehicle ages certain parts can contribute to a worsening of the issue. TB, MAFS, Fuel Pumps, 02 Sensors, Coils/Plugs etc. He mentioned with emphasis that quite a few of the aftermarket coils that are out there are suspect. He also said that because the maintenance $$$ are so high on these and the secondary market value of the vehicle is so low he really sees very few that are over 5 years old in the shop and when he does they typically have quite a few stored codes because of lack of maintenance and in general the "system" on first gen Cayenne's don't handle multiple fault/stored codes well - he said it can have the similar effect that a failing battery can have. (this made me laugh quite a bit) Where the motor and trans mount(s) contribute to the issue is in the "seat of your pants feel" through the chassis. Once the Hydraulic motor mounts start to and all eventually fail they are no longer masking the poor idle and you then feel it. He said it's like night and day.

Share this post


Link to post
Share on other sites

Service TB & new/ clean MAFs plus new 02 sensors are on my replace list anyway with 125k on the clock and mounts will be last. I promise Surametric will also be purchased - but I've covered the few of his list.

Share this post


Link to post
Share on other sites

Or shall I clean MAFs?

 

The MAFs are not needed for starting or idle. You can disconnect them and the car will start and idle fine (you will get a fault code though).

Share this post


Link to post
Share on other sites

For sure tho the 02s should get replaced by now and clean the throttle body?

Share this post


Link to post
Share on other sites

I recently (3 weeks ago) purchased a 955 Cayenne Turbo and had the same idle drop issue. After purchasing, I discovered the water pump was leaking which seemed like a good DIY project that would allow me to get familiar with the vehicle. The first water pump I purchased and installed was an aftermarket Laso and in less than a week it began making a groaning noise. During the replacement I pulled and cleaned the throttle body and after putting everything back together it made no difference with the idle drop even after performing the throttle position relearn sequence.

 

Last week it was unusually cold here and when going over speed bumps the front of the vehicle was making a noticeable scrubbing/squeaking noise. I purchased some spray silicone approved for plastics and bushings then sprayed everything on the front end down. I decided to open the hood and empty the can on the engine for some added protection on the hoses. While spraying I discovered a couple of hose leaks. One was on the purge solenoid inlet hose that sits to the right of the throttle body and the other was on the small line that hooks in under the intake "T" pipe. The one under the intake surprised me because I thought I had pushed it up within an inch of its life but you really have to fully seat it onto the nipple so it doesn't leak. Fixing those two leaks made a huge difference and the idle drop was almost gone.

 

Last Saturday morning I took everything back apart and installed another new water pump but this time used one from the Porsche dealership. While everything was torn down I replaced some of the older hose clamps and made extra sure every hose was on and secure with no leaks. When putting the "T" pipe back on I finally got the nipple lined up perfectly with the fitting and saw how much further it actually seats together. Before starting the vehicle I performed another throttle position relearn. Knock on wood I have driven over 300 miles since then with no idle drop issues! It's made a huge difference in the way the Cayenne performs. I couldn't be more thrilled. Oddly enough my starter was grinding after almost every start and it has not done it since. I'm assuming maybe the auto start feature was keeping the vehicle starter engaged because the engine was not starting with enough rpms for it to sense to disengage the starter. Whatever the case may be I no longer am having the idle drop.

 

One more thing to note is there is a huge difference in how steady the temperature is after replacing the water pump with the Porsche part. With the original water pump that was worn out and the new Laso I had temperature fluctuates for the few weeks I was able to drive the car while they were installed. With the Porsche water pump I am at a steady 180 while driving and at idle. There is also a difference in the pitch of the impeller vanes between the Porsche and Laso. The Porsche impeller seems to have more pitch on the vanes. Maybe it moves more fluid? Not sure but, again, I am thrilled with how smooth the Cayenne is running as of this writing. The final 2 repairs I have to make are the tensioner pulley and the drive shaft. I will update about the idle to confirm if it remains smooth over time.

Share this post


Link to post
Share on other sites

Motor mounts are the remaining culprit. I do have Durametric now is there something specific I can test on the MAFs and 02s? All new fuel delivery system, vacuum lines, starter, water pump and thermostat, plugs and coils, front lower control arms, expansion talk and lines.....

The idle is pretty much fine except when you first start the CTT. I think I want to do air intakes and the fabspeed pipes now just for S&Gs.

Edited by ALEV8

Share this post


Link to post
Share on other sites

I had my motor mounts replaced 1 month ago as I was getting vibrations through the chassis especially when the idle dipped briefly coming to a stop.

Am happy to report that although the idle dip is still observed on the tacho, no vibration can be felt through the chassis anymore.

It is smooth as silk.

Changing the mounts will mask the vibration, but not cure it.

Still worth doing for vibe free performance.

Share this post


Link to post
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.