Welcome to 911UK
The only place for Porsche, 911uk is the definitive enthusiast and resource site for the Porsche 911.
Registration is fast, simple and absolutely free, so join up today for full access to the site and benefit from latest member offers.

Porsche Classifieds
Sell Your Porsche on 911uk
Create a Free Classified Advert
Search Ads
Classified Adverts FAQ
Trade Classified Information
Buyer & Seller Fraud Protection
Consumer Rights Act
Pre Purchase Inspection (PPI)
Porsche Car Sourcing
Porsche Cars Wanted
Official Porsche Centre Reviews
Model
Stock
Porsche 911
992 : 2019- 1
991 : 2011-2019 0
997 : 2004-2012 1
996 : 1997-2005 31
993 : 1993-1998 5
964 : 1989-1993 2
Carrera 3.2 : 1983-1989 3
Carrera SC : 1977-1983 1
930 Turbo : 1975-1989 0
Early 911 : 1964-1977 0
Porsche Other Models
Classic : 1950-1965 0
Boxster : 1997- 22
Cayman : 2005- 14
Cayenne : 2003- 2
Macan : 2014- 2
Panamera : 2009- 1
912-914-924-928-944-968 1
959 - CarreraGT - RaceCar 0
Car Parts For Sale & Wanted
Other Items For Sale & Wanted
Wheels Tyres For Sale & Wanted
Number Plates For Sale Wanted

Porsche Services
Porsche Body Shop Repair
Paint Protection & Wrapping
Porsche Classic Insurance
Porsche Classic Parts
Porsche Classic Restoration
Porsche Design Collection
Porsche Engine Gearbox Rebuild
Porsche Heritage & History
Porsche News
Porsche Picture Gallery
Win a New Porsche 911

Porsche Parts
Body Parts, Body Styling
Brakes, Clearance
Electrical, Exhausts
Engine Cooling, Engine Electrical
Engine Rebuild, Heating Cooling
Interior Incar, Lighting
Rubber Seals, Service Parts
Steering, Suspension
Transmission, Workshop Tools
Early 911, 911 - 930, 928 - 968
964 - 993, 996 - 997, Boxster
Cayman, Cayenne, Panamera

Porsche Model Range
911 [992] 2018-Current
Porsche 911 [992]
911 [991] 2011-2019
Porsche 911 [991]
911 [997] 2004-2012
Porsche 911 [997]
911 [GT] GT1-GT2-GT3
Porsche 911 [GT]
911 [996] 1997-2005
Porsche 911 [996]
911 [993] 1993-1998
Porsche 911 [993]
911 [RS] RS-RSR
Porsche 911 [RS]
911 [964] 1989-1993
Porsche 911 [964]
911 3.2 1983-1989
Porsche 911 3.2 Carrera
911 SC 1977-1983
Porsche 911 SC
911 [Early] 1964-1977
Porsche 911 [Early]
Boxster & Cayman
Porsche Boxster & Cayman
Cayenne & Panamera
Porsche Cayenne & Panamera

911uk Site Partners

Post new topic   Reply to topic
Author Message
Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16543
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Wed Jun 08, 2016 3:31 pm    Post subject: Reply with quote

Normal service has been resumed Sad


So - this is the script (any advice welcome):

Yesterday I had some spare time so I thought I'd have a look at where the knock sensors are, with the intention to change them if they were the guilty parts.

Here's the sequence of operations to help me understand what's going on:

1. Car up on ramps (just so I'm not bent over all the time).
2. MAF disconnected & airbox removed.
3. Throttle body disconnected and removed.
4. Vac pipes disconnected from rubber plenum sleeves, plenum and each rubber sleeve removed.
5. Knock sensors located and disconnected.
6. Oil sensor disconnected and electrical connector to vac pipe block above the alternator also disconnected to enable me to move wires around and help with access to knock sensors.
7. Both knock sensors removed, inspected for any cracks, etc. and mating faces cleaned up with some emery paper.
8. Knock sensors replaced the opposite way round (L on R & R on L).
9. Everything else reconnected, plenum cleaned out and refit, throttle body refit and airbox. Reconnect MAF, throttle body, etc.
10. Turned over and fired up perfectly.
11. Went for a 5 mile spin, engine ticking over beautifully - plugged code reader in and watched live data - all stable figures and left/right banks identical.
12. Had my Tea, went for a 12 mile spin, got home, car still ticking over great.
13. Went to work this morning, tickover on arrival degrading.
14. Came home this afternoon and running lumpy again. Plugged code reader in again - live data show fluctuating fuel trims and left bank in minus figures whilst right bank in positive figures.

So - what's the verdict?

Here's a few ideas from me:

(ps. car was running beautifully last night when I went for a spin)


1. One of the (or both) knock sensors is playing up and causing the problem. Taking them off, giving them a shake and refitting them temporarily sprung them back in action.

2. Disconnecting one of the other components for a couple of hours and reconnecting it has reset something and after a few miles of driving has tuned it back to how it was.

3. Oil getting in through the vac pipes into the plenum and cleaning it out yesterday made it run fine, until more oil got back in again. Evidence of oil in the plenum when removed was only light coating on the lower inside faces of it .

4. The plenum was fit incorrectly and causing a vac leak. refitting it stopped the leak until it's gone through the motion of getting hot/cold/hot/cold.

Dont know


I'm in the position of:

1. Buy two new knock sensors, fit them and see if it cures it.

2. Remover the airbox, throttle body & plenum AGAIN, clean out and see if the car temporarily runs ok.

3. Torch the F*!£ker!!!!!!! Gun Fire


frustrated


Any ideas guys??????????


Oh - and to top all this off, my right back box sounds like it's started blowing like crazy, even though it's a 2 year old Dansk and no signs of any leaks in the hole system.

This car is starting to get to me nooo
_________________
2000 Manual 996 C4 Arctic Silver Convertible


 
  
View user's profile Send private message
   
deMort
Dijon


Joined: 21 Mar 2015
Posts: 7008
Location: Brighton


PostPosted: Wed Jun 08, 2016 7:13 pm    Post subject: Reply with quote

Some info on knock sensors ..

http://vems.hu/vt/help/v3/v3_knock_control.html

I think its unlikely the knock sensors are faulty .. possible but very unusual and with out a fault code ? hmm ...

Only way to prove is to scope them im afraid.

I take it you tightened them up to 20nm , they are pressure sensitive so over tightening them will break them , and you can see from the link what they do and how they work so ill not repeat that.

i didnt read all the posts so can you confirm for me this is an idle problem ?

Can you post the adaption figures you have .. which must be a few days driveing since you cleared any fault codes as this will reset the adaption figures.

Atm it sounds like 1 bank is rich and the other is weak .. thats into the lambda sensor / maf sensor fault area or exhaust fault .. blocked cat etc , air leak near lambda sensor .. that sort of thing.

If we are talking idle then can you see the throttle pedal values and throttle position values ?

If so post them and also watch them as you depress the throttle slowly .. tell me at what figure the revs increase and also with the air con on if you can maintain 1500 rpm .. im hopeing you can as if you have basically 1k or 2k with a/c on and cant maintain inbetween with engine hot then its similar to a fault i had recently .. that was a DME .. but that did show random throttle valve fault codes.

Ill look at the data and check my fuel sheets at work ( different ones for different models and i havent memorised them Smile ) i can also chat with the guys and see if we can think of anything ..

Please bear in mind .. its a hell of a lot easier to fault find when i can work on the car than here but ill do my best.

Post here or PM .. either is good.
 
  
View user's profile Send private message
   
Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16543
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Wed Jun 08, 2016 7:25 pm    Post subject: Reply with quote

I can't save data on my code reader. I've read a couple of other posts/threads that suggest a faulty knock sensor can play havoc with the tickover.

What I can't understand is I take them off, have 20 miles of perfect driving (with identical readings off both banks sensors and stable timing reading) and then it starts to deteriorate back to where it was.

I could really do with plugging a duramteric in, but I'm not local to any specialists - nearest is Colne at 16 miles away + the fact I'm broke at the moment.
_________________
2000 Manual 996 C4 Arctic Silver Convertible


 
  
View user's profile Send private message
   
Endex
Monza


Joined: 10 Jan 2016
Posts: 209
Location: Preston, Lancashire


PostPosted: Wed Jun 08, 2016 7:59 pm    Post subject: Reply with quote

alex yates wrote:
[size=18]Normal service has been resumed

I'm in the position of:

1. Buy two new knock sensors, fit them and see if it cures it.

2. Remover the airbox, throttle body & plenum AGAIN, clean out and see if the car temporarily runs ok.

3. Torch the F*!£ker!!!!!!! Gun Fire


frustrated


Any ideas guys??????????


Oh - and to top all this off, my right back box sounds like it's started blowing like crazy, even though it's a 2 year old Dansk and no signs of any leaks in the hole system.

This car is starting to get to me nooo

Alex - option 3 is the cheapest Surprised But.................
You'll have to walk to the Pub and we'd miss your wit, charm and charisma so man up and get option 1 and 2 done and cross your fingers!
Good luck Cool
_________________
Porsche 997.1 C4S, Manual
 
  
View user's profile Send private message
   
deMort
Dijon


Joined: 21 Mar 2015
Posts: 7008
Location: Brighton


PostPosted: Wed Jun 08, 2016 8:00 pm    Post subject: Reply with quote

With your code reader can you see the above values and write them down to post or is it just basic fault codes ?

Knock sensors are possible .. its just that its a pretty rare thing and for 2 to go at the same time .. only times ive ever changed them is due to rodent damage .

Im thinking cost atm .. replaceing something without knowing if its the fault kinda goes against what i do.

trouble is you need to scope them to prove and even then the signal pattern looks pretty much like junk .. its just an ac wave pattern.

Im interested in the adaption values .. they tend to tell us a fair bit about long term running .. depending on how far out they are gives a clue as to what might be wrong.

Also the trouble with intermitant faults is they are just that .. always a bitch to find .. you have to gather every clue you can as the the fault is never there when you test it.

I was thinking of tank venting as well .. car has to be hot for that to start .. but really any fault on that would affect both banks.

Have you replaced the MAF sensor in the last few years ? i wont go into details but that is a possible.


Btw intermitant faults have a habbit of not comeing back if you have touched something ..always for me at least its never related when i finally find whats wrong .. so .. touching something is no gauarentee that that is the problem im afraid.

Im not sure if my link said how knock sensors work but they are basically a crystal thats gives off a small electric charge when under pressure .. ( same as your lighter if you smoke ) .. so a pressure wave ( a knock ) would generate a voltage that the dme can respond to and alter the timing accordingly , as such i would expect them to work or not work .. hence im not sure thats the fault .. and hence i dont want you spending money without more tests .. if you follow me Smile
 
  
View user's profile Send private message
   
Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16543
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Wed Jun 08, 2016 8:12 pm    Post subject: Reply with quote

At the moment its gone from intermittent fault to intermittent running well.

Think I'll strip the plenum down, clean it out again and see if it runs well. If it's still lumpy, then get a couple on knock sensors. Good chance if it is a knock sensor, it's only one, but may as well do both whilst I'm in there.


Checked my spark plugs the other day and they all look perfect and identical on both banks. Next time I hear someone on here bitch about changing plugs or coil packs I'm gonna show them my hands and arms after taking those knock sensors off (with the engine hot!!!!!!) Grin

Now they are a swine of a job - especially when you drop a 12mm socket on top of one bank!!
_________________
2000 Manual 996 C4 Arctic Silver Convertible


 
  
View user's profile Send private message
   
deMort
Dijon


Joined: 21 Mar 2015
Posts: 7008
Location: Brighton


PostPosted: Wed Jun 08, 2016 8:18 pm    Post subject: Reply with quote

You have my sympathys .. hot engine plus that kind of job .. its not pleasent .

Take a few pictures as you go please , vacumn pipes , amount of oil in throttle .. that sort of thing .. anything helps me atm to be honest Smile
 
  
View user's profile Send private message
   
mzmini
Barcelona


Joined: 30 Jan 2015
Posts: 1438
Location: Somerset


PostPosted: Wed Jun 08, 2016 8:21 pm    Post subject: Reply with quote

I feel for you Alex good luck with it hope you can get to the bottom of it soon Thumb
_________________
997 3.8 C2S
987 Boxster 3.4S
Disco 3
2012 VW Polo

1964 1071 Cooper S
1964 1071 Cooper S 1991 Pirelli Classic winner
1971 1275 Cooper S as new time warp
1996 106 Peugeot van (pride of the fleet)
 
  
View user's profile Send private message
   
Griffter
Spa-Francorchamps


Joined: 22 May 2016
Posts: 335



PostPosted: Thu Jun 09, 2016 6:39 am    Post subject: Reply with quote

Re step 14 in your sequence, I'm not familiar with the specific set up but in my experience, differences left to right indicate a fault on one side or the other, not with a common component (such as the maf, plenum or throttle body). More likely a vacuum / manifold leak or o2 sensor on one side imo.

Good luck.
 
  
View user's profile Send private message
   
ELA
Barcelona


Joined: 30 Aug 2011
Posts: 1295
Location: Nurburgring Doorstep


PostPosted: Thu Jun 09, 2016 8:45 am    Post subject: Reply with quote

Demort wrote:
Some info on knock sensors ..

http://vems.hu/vt/help/v3/v3_knock_control.html

I think its unlikely the knock sensors are faulty .. possible but very unusual and with out a fault code ? hmm ...

Only way to prove is to scope them im afraid.

I take it you tightened them up to 20nm , they are pressure sensitive so over tightening them will break them , and you can see from the link what they do and how they work so ill not repeat that.

i didnt read all the posts so can you confirm for me this is an idle problem ?

Can you post the adaption figures you have .. which must be a few days driveing since you cleared any fault codes as this will reset the adaption figures.

Atm it sounds like 1 bank is rich and the other is weak .. thats into the lambda sensor / maf sensor fault area or exhaust fault .. blocked cat etc , air leak near lambda sensor .. that sort of thing.

If we are talking idle then can you see the throttle pedal values and throttle position values ?

If so post them and also watch them as you depress the throttle slowly .. tell me at what figure the revs increase and also with the air con on if you can maintain 1500 rpm .. im hopeing you can as if you have basically 1k or 2k with a/c on and cant maintain inbetween with engine hot then its similar to a fault i had recently .. that was a DME .. but that did show random throttle valve fault codes.

Ill look at the data and check my fuel sheets at work ( different ones for different models and i havent memorised them Smile ) i can also chat with the guys and see if we can think of anything ..

Please bear in mind .. its a hell of a lot easier to fault find when i can work on the car than here but ill do my best.

Post here or PM .. either is good.


Demort, I have read a few posts you have written now on this forum and would like to say what an asset you are for everyone here. Thank you for the support, the likes of which you have shown here worship
Alex, the last comment by Grifter above concurs with my thoughts. I wish you the best of luck with finally getting to the bottom of this issue Thumb
_________________
CLR996 1086kg bespoke design
 
  
View user's profile Send private message Visit poster's website
   
digby
Trainee


Joined: 10 Dec 2010
Posts: 91



PostPosted: Thu Jun 09, 2016 1:01 pm    Post subject: Reply with quote

Hi Alex
been following this with interest

I am intrigued by the difference in fuel trims between banks - i think you need to understand why there is a difference

It could be the O2 sensors (need to swap them round maybe or scope them)
or it could be some sort of leak (vacuum or fuel depending on rich or lean)

If you can show that the O2 sensors are working ok then you can systematically search for leaks with quick start / propane gas)

I recently spent some hours watching youtube videos from a guy called schrodingers box - quite interesting
 
  
View user's profile Send private message
   
Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16543
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Thu Jun 09, 2016 1:52 pm    Post subject: Reply with quote

digby wrote:
Hi Alex
been following this with interest

I am intrigued by the difference in fuel trims between banks - i think you need to understand why there is a difference

It could be the O2 sensors (need to swap them round maybe or scope them)
or it could be some sort of leak (vacuum or fuel depending on rich or lean)

If you can show that the O2 sensors are working ok then you can systematically search for leaks with quick start / propane gas)

I recently spent some hours watching youtube videos from a guy called schrodingers box - quite interesting


If the fault was intermittent, then there most of the time, then disappears when I swap the knock sensors, remove the plenum , cleanout and refit, then return the day after, how can you explain any of the above?

Previously checked for leaks with easy start about 4 pages back.

Confused
_________________
2000 Manual 996 C4 Arctic Silver Convertible


 
  
View user's profile Send private message
   
digby
Trainee


Joined: 10 Dec 2010
Posts: 91



PostPosted: Thu Jun 09, 2016 2:06 pm    Post subject: Reply with quote

Hi Alex

intermittent symptoms are (i guess) generally caused by intermittent problems like a bad electrical connection or a leak that only happens under certain circumstances.

these are of course the worst problems to track down .....

you have clues though - the difference between banks 1 and 2 should help a lot

if you make the fuel trim problem change banks by swapping something then you are in business

watch the videos this guy has made and if your diagnostics can do short and long term fuel trims and actual graph the O2 sensor outputs then you are in business

good luck

p.s. when my 996.1 had a bad idle it needed (had) a new camshaft solenoid thing
 
  
View user's profile Send private message
   
deMort
Dijon


Joined: 21 Mar 2015
Posts: 7008
Location: Brighton


PostPosted: Thu Jun 09, 2016 7:00 pm    Post subject: Reply with quote

[/quote]

Demort, I have read a few posts you have written now on this forum and would like to say what an asset you are for everyone here. Thank you for the support, the likes of which you have shown here worship
[/quote]

Very decent of you to say so sir .. just trying to help though Smile

Maf sensor i mentioned .. it was for a reason .. rich / lean on opposite banks .. say we have an air leak on bank 1 .. not good but the car will adapt by injecting more fuel and so run fine .. but a faulty maf can over and under fuel .. the maf is not obvious as the adaptions point to something else but trust me it is possible ..

You can also get a misfire on say 4,5 and 6 which points to a vario cam fault .. again it can be the maf .. been there seen it and got caught out .. hence i mentioned it.

Also im looking for difficult to find faults .. something unusual because im dam sure Alex knows what hes doing so pointing out the obvious is in my way of thinking a bit insulting to him .

Anyways just pointing out why may be disconnecting the maf and driveing is a possible if unlikely fault .. or if its been replaced in the last few years then it can be eliminated.

Im going to read the entire post and see what i can come up with .. back in 20 mins or so i guess .. its a long post !
 
  
View user's profile Send private message
   
deMort
Dijon


Joined: 21 Mar 2015
Posts: 7008
Location: Brighton


PostPosted: Thu Jun 09, 2016 7:28 pm    Post subject: Reply with quote

ragpicker wrote:
My friend (who is my Indy) had this issue on a car he had in a few weeks ago.
He spent literally days trying to figure it out - changing lambdas, crank sensor, throttle sensor, plugs, packs, earth points, engine out looking for air leaks etc. I'm not joking he spent 3 straight days on it (this is the reason my car took so long to get in to have my problem sorted).

He has also got a 3.4 carrera. In the end he took his ECU and loom from his car and put it into the car with the problem. Bingo! Problem of rough idle sorted instantly. Symptoms were exactly the same as you have described.

When he plugged the faulty cars ECU into his car - the problem was there again.

This is the 3rd time he has seen this problem apparently.

Fortunately ECU's with keys can be found on eBay for about £100 but it must be the same engine model number as yours. There was a bit of an ECU changeover at the end of the 3.4 production run apparently.

Give Nelson Porsche a ring (stockton on tees) - say Ragpicker sent you Wink


I got as far as this then stopped reading .. its also what i was thinking and i posted before reading this which makes it even worse im afraid as 2 of us have come to the same conclusion independantly.

Mine was a bitch of a problem to find as well but i did have thottle body codes , random ones but a pointer at least.

Heres what i tryed to try and prove it , which i want you to try please ..

You know where the dme is .. it gets hot .. very hot , stupid place to put it if you ask me .. remove the carpet , remove the bracket and have the dme face up , so hopefully it stays cooler , then try a drive and see if any difference.

A reprogram is a possible but my one we just replaced it to fix it.

Couple of other things you may want to consider , i made some notes as i was reading from the beginning ..

Tank venting , happens at operating temp , need to find a way of blocking the pipe , vent pipe left open i think would be safest and seeing if that makes any diff .. not sure the best way to do it .. but you know what i mean.

Lambdas .. they work from about 1 min after cold .. fault would be there before operating temp i feel.

Vario cam is a possible , it will affect idle .. but ive always seen rough running or misfires with that fault , it wont stop the car from starting either .. possible but im unsure .

Erm the pict of the AOS .. thats an earth lead there next to it .. might be an idear to clean it or at least check its a good contact as it doesnt look like it lol ... not sure off hand what its for but it will be sensor related .. probably nothing to do with the fault .. but even so Smile

The fault itself .. dme monitors crank sensor and so rpm , if it drops below 700 it will increase the throttle to raise the rpm .. this is a constant thing so it will continually alter the throttle to maintain idle.

Your car is not reacting untill it drops almost to stall then bangs open the throttle to catch it .. over reving to a point and then repeating .. crank sensor is main input .. dme is in charge , throttle pedal position and throttle position all have inputs to decide idle .. hence i wondered if you could see any of these values ..

Pedal can cause something like this .. its yet another possible .. but im also back at the DME as well ..

Very hard without spending a fair bit of time on the car to help .. but hopefully something ive posted will be usefull .. please keep posting though of what you do / decide .

As i say to some of the guys with a bitch of a problem .. Good Hunting .


EDIT one other thing i did think of which you may already have tryed is check the fuel pressure at the rail .. low pressure wont give fault codes and can cause varying faults.
 
  
View user's profile Send private message
   
Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16543
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Fri Jan 18, 2019 3:53 pm    Post subject: Reply with quote

systemmeister wrote:
Is it lumpy as a cement mixer?

I had similar symptoms but mine was vario cam solenoid.


Problem now sorted. Was variocam solenoid on Bank 1. Embarassed

Shoulda listened to you Jon in the 1st place bonk
_________________
2000 Manual 996 C4 Arctic Silver Convertible


 
  
View user's profile Send private message
   
Luddite
Nürburgring


Joined: 18 Dec 2018
Posts: 412
Location: Scotland


PostPosted: Fri Jan 18, 2019 4:14 pm    Post subject: Reply with quote

All a bit late in the day and would not have solved your issue Alex... When trying to detect air leaks I use a length of hose one end to my ear the other used to move around the areas of interest...

Showing my age again, I also used that system for balancing carburettor air flow in twin/multiple carb set-ups.. Simple cheap and no need for a fire extinguisher.. Question
 
  
View user's profile Send private message
   
Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16543
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Mon Feb 04, 2019 7:31 pm    Post subject: Reply with quote

Over 2 weeks of perfect running now. I'm convinced now the problem is resolved. Spent 2 weeks waiting to fire it up when hot and the tickover be lumpy.

Alex is a happy man. Smile
_________________
2000 Manual 996 C4 Arctic Silver Convertible


 
  
View user's profile Send private message
   
Display posts from previous:   
Post new topic   Reply to topic   All times are GMT - 12 Hours
Goto page Previous  1, 2, 3, 4, 5, 6
Page 6 of 6

 
Jump to:  

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You can attach files in this forum
You can download files in this forum
You cannot post calendar events in this forum