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New997buyer
Fuji


Joined: 17 Oct 2010
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PostPosted: Fri Jul 31, 2015 11:38 pm    Post subject: Reply with quote

Laughing
 
  
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Alex
Le Mans
Le Mans


Joined: 06 Mar 2014
Posts: 16529
Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Sat Aug 01, 2015 5:17 pm    Post subject: Reply with quote

So, 24 hours after the car running sweet as a nut on several occasions, it's now gone back to this!

At least now I know it is definitely ECU related and not an air leak or dodgy coil pack. At a guess, I'd say after the ECU reset, it's trying to retune itself and doing it wrong????? Confused Confused Confused

In the video I'm just firing it up, no throttle or anything - all the cars doing.


Open Youtube Page

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Alex
Le Mans
Le Mans


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Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Tue Aug 25, 2015 7:12 pm    Post subject: Reply with quote

****UPDATE****

So last Wednesday I treated the old motor to a set of Bosch coil packs (knowing that it could quite possibly be the reason for the rough idle) as it was getting due looking at the state of them and no history in the receipts of them being done.

Once done, give the ECU a reset so that everything was fresh with a clean sheet.

Car carried on as normal with a poor tickover.
Going on holiday next Tuesday in it to the South of France so want it running right.

Anyhow, had it in with my mechanic tonight, taking with me all the DME specs at tickover so we can compare with what the car's actually reading and hopefully identify where the issue is.
Get down there and car is running sweet as. All the readings are fine and now I can't getting running bad!!!

frustrated frustrated frustrated frustrated frustrated frustrated frustrated frustrated
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Alex
Le Mans
Le Mans


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Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Thu Aug 27, 2015 9:14 am    Post subject: Reply with quote

Quick update and hopefully some help.

Last night spent a good couple of hours with the live data being read as it was running poo.

Looks like bank 1 is running leaner than bank 2 (as the o2 sensor readings were consistently showing lower voltage on 1 than 2) and also the STFT - short term fuel trim percentage was in minus figures on bank 1 and positive on 2???????????

Any ideas guys on what's wrong?

Dont know Confused nooo Neutral
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Airborne9
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PostPosted: Thu Aug 27, 2015 11:11 am    Post subject: Reply with quote

apologise if this has already been mentioned, but have you changed your knock sensor?
 
  
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Alex
Le Mans
Le Mans


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

2000 Porsche 996 Carrera 4

PostPosted: Thu Aug 27, 2015 11:13 am    Post subject: Reply with quote

No. Isn't there 2 of them on mine? (M96.04 engine)

I was asking my mechanic last night if this could be the culprit.
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Chris_in_the_UK
Estoril


Joined: 19 Mar 2014
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PostPosted: Thu Aug 27, 2015 11:16 am    Post subject: Reply with quote

Have you read this Alex?

http://www.obd-codes.com/faq/fuel-trims.php
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Airborne9
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PostPosted: Thu Aug 27, 2015 11:17 am    Post subject: Reply with quote

I would put quite a bit of money on it being the knock sensor mate. im unsure whether you have two or not.
 
  
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Harv
Suzuka


Joined: 18 Sep 2014
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PostPosted: Thu Aug 27, 2015 11:17 am    Post subject: Reply with quote

Hi Alex

Sounds like this is giving some grief.
Have you now ruled out that this is an ECU intermittent fault?

Since you mention there's a difference in the richness between banks I would be inclined to suspect an O2 sensor problem. I'm not sure which of the pre or post cat sensors control mixture but would certainly be tempted to try swap the sensors over side for side and see if the lean issue presents itself on the opposite bank.

I did have a ticking over issue on mine after I had the engine in bits and that turned out to be O2 sensors plugged into the wrong sockets on the loom. They are located next to the back of the airbox (4 plugs in total).

I'm assuming you don't have any logged faults (interestingly I didn't get any when I had them plugged incorrectly either)..


Thumb
 
  
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Alex
Le Mans
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Joined: 06 Mar 2014
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Location: The Ribble Valley, Lancashire

2000 Porsche 996 Carrera 4

PostPosted: Thu Aug 27, 2015 11:31 am    Post subject: Reply with quote

Cheers Chris, read something similar this morning. Will have a good read of this too.

Just gonna have some lunch then get it up on ramps and have a look round the sensors as well as reading live data again. Was thinking of swapping o2 sensors but a bit scared of breaking them whilst trying to undo them. Do they come out easy enough?

Haven't ruled out the DME being faulty yet (ECU)

My mechanic is convinced I've got an injector problem.

Seems worse at times than others though so looks like an intermittent faulty sensor reading to me.
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Harv
Suzuka


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PostPosted: Thu Aug 27, 2015 11:44 am    Post subject: Reply with quote

The O2 sensors will be a pain in the ass to remove and you may need oxy and cold water to get them out.


The plug the wires and looms maybe be long enough to allow over crossing the left & right sides in the engine bay and so you will fool the ECU with readings off the opposite bank if you have the piwis or durametric for live data
 
  
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Alex
Le Mans
Le Mans


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

2000 Porsche 996 Carrera 4

PostPosted: Thu Aug 27, 2015 11:45 am    Post subject: Reply with quote

Harv wrote:

The plug the wires and looms maybe be long enough to allow over crossing the left & right sides in the engine bay


nooo they're not.
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nickd
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Joined: 10 Jun 2015
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PostPosted: Thu Aug 27, 2015 11:52 am    Post subject: Reply with quote

Does it only run badly on tickover? Is it rough on WOT too? It will likely be running closed loop on tickover, so using the O2s, but generally won't use the O2s on WOT so might help with diagnosis.
 
  
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Alex
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PostPosted: Thu Aug 27, 2015 12:36 pm    Post subject: Reply with quote

only on tickover
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Airborne9
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PostPosted: Thu Aug 27, 2015 1:02 pm    Post subject: Reply with quote

on idle, give it a tiny amount of gas and let it drop, does it almost stall or stall completely?
 
  
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Harv
Suzuka


Joined: 18 Sep 2014
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PostPosted: Thu Aug 27, 2015 1:15 pm    Post subject: Reply with quote

Darn, back bumper off then may make access easier.

Have you had a quote from a specialist breaker for an ecu? You might get a sale or return from one of them if you explain the issue.

This thread has jogged my memory that I had an O2 sensor fault on a mk2 TT and that turned out to be a broken wire in the loom which took 12v to the sensor, sometimes it was fine and then it would start playing up. I'd given up until one day I spotted a chaffed loom.

Id say it's time to get busy swapping some sensors or the ECU Thumb

Last edited by Harv on Thu Aug 27, 2015 1:30 pm; edited 1 time in total
 
  
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Harv
Suzuka


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PostPosted: Thu Aug 27, 2015 1:26 pm    Post subject: Reply with quote

Double post PC
 
  
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Alex
Le Mans
Le Mans


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

2000 Porsche 996 Carrera 4

PostPosted: Thu Aug 27, 2015 1:44 pm    Post subject: Reply with quote

Airborne9 wrote:
on idle, give it a tiny amount of gas and let it drop, does it almost stall or stall completely?


Yeah some of the time. In fact it has stalled a couple of times.
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Airborne9
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PostPosted: Thu Aug 27, 2015 2:28 pm    Post subject: Reply with quote

its all sounding like a knock sensor to me! ive had this before
 
  
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Alex
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2000 Porsche 996 Carrera 4

PostPosted: Thu Aug 27, 2015 2:31 pm    Post subject: Reply with quote

So if it is, if I put 95 ron in, it should run fine???? Dont know
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