23 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCH996 running rough as an old goat
Leading reported evidence
Install ecu is not an exact match
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed
From what you said, it appears that the currently installed ECU is not an exact match for your car.
Leading evidence: 'Install ecu is not an exact match' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, the most frequently mentioned possible cause is 'valve' (1 discussions; 0 report identifying it and 1 suggest it). The most frequently discussed action is 'Check serpentine belt and all the accessories and things' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
Air tested which rules that out .most things have been ruled out , im no mechanic but I am an engineer so understand how things work .
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause · Original poster
Then came the issues , the car would not start or infact do anything basically the immobiliser would not let anything happen , new immobiliser same problem so they changed the ecu , done problem solved everything as it should apart from it was running lumpy Occasionally , turned out to be a valve under the rocker cover (excuse my ignorance ) that was changed .
Check serpentine belt and all the accessories and things
Suggestion or failed attempt
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion
You checked the serpentine belt and all the accessories and things that run off it?
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
Discussions that contain suggestions
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
Then came the issues , the car would not start or infact do anything basically the immobiliser would not let anything happen , new immobiliser same problem so they changed the ecu , done problem solved everything as it should apart from it was running lumpy Occasionally , turned out to be a valve under the rocker cover (excuse my ignorance ) that was changed .
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
Then came the issues , the car would not start or infact do anything basically the immobiliser would not let anything happen , new immobiliser same problem so they changed the ecu , done problem solved everything as it should apart from it was running lumpy Occasionally , turned out to be a valve under the rocker cover (excuse my ignorance ) that was changed .
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
Car has had full plugs coil packs oil change , smoke tests , fuel pump test everything has come back correct , starts ok but as soon as it gets warm it runs like it has had diesel poured into it, my mechanic now believes that the ecu we fitted is possibly from a 996 with 4 exhaust sensors not 2 like mine !!!!
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suggestion · Original poster
Then came the issues , the car would not start or infact do anything basically the immobiliser would not let anything happen , new immobiliser same problem so they changed the ecu , done problem solved everything as it should apart from it was running lumpy Occasionally , turned out to be a valve under the rocker cover (excuse my ignorance ) that was changed .
These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.
valve
No successful repair reported for this finding.
0
Identified cause
1
Suspected cause
0
Reported fixes
Read evidence and context
Discussions that suspect a cause
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Suspected cause · Original poster
Then came the issues , the car would not start or infact do anything basically the immobiliser would not let anything happen , new immobiliser same problem so they changed the ecu , done problem solved everything as it should apart from it was running lumpy Occasionally , turned out to be a valve under the rocker cover (excuse my ignorance ) that was changed .
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
23 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261027T035758Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Evening all, desperate for help with my 1998 996 c4 cab,,ok so the car has been in a garage for 5 months , started with ims change That was completed ! Then came the issues , the car would not start or infact do anything basically the immobiliser would not let anything happen , new immobiliser same problem so they changed the ecu , done problem solved everything as it should apart from it was running lumpy Occasionally , turned out to be a valve under the rocker cover (excuse my ignorance ) that was changed . Car has had full plugs coil packs oil change , smoke tests , fuel pump test everything has come back correct , starts ok but as soon as it gets warm it runs like it has had diesel poured into it, my mechanic now believes that the ecu we fitted is possibly from a 996 with 4 exhaust sensors not 2 like mine !!!! Can anyone confirm this would cause this ???? Please desperate just want my car back for the summer , thanks in advance .. den
Yes they have done a good few previous to mine !! Starts and sounds nice runs smooth , and then as soon as it gets even a bit warm bogs down . No smoke , no strange noises , no lights
From what you said, it appears that the currently installed ECU is not an exact match for your car. I would start my diagnosis there. Do you still have the old ECU? I would compare model numbers on the ECUs and do some searching on the web to figure out what you currently have installed. If the new ECU is looking for four O2 sensor inputs and there are only two, it may be in a default "limp mode".
This is what he is thinking , but on research they all seem to have the same part numbers on a few different kinds as it�s an early 1998 I think they updated every 2 years , my mech has spoke with another couple of Porsche specialists that he has had ties with in the past and no one seems to be able to confirm . Also called a few specialist breakers and they were unaware there was a difference
Sorry I did reply not sure where it disappeared to !!! It seems most Porsche mechs or breakers didn�t seem to know if there was a difference between the ecus but it seems there were a fair few !! And it seems the chances of getting the exact one we need gurenteed from somebody is a bit hit and hope ! With all this said and done , with new coil packs, new plugs, new (egr valve I think) , new idle control valve, new plug tubes as was a air leak, now smoke tested , no codes , what else could cause such drastic engine bogging down and hunting when mechanically things seem ok, as I said previous no smoke or lights , just bogging down once warm
I think you need to be more methodical in figuring out what the problem is, don't throw parts at the car unless you have a reason to.
Good idea to start with a code reader, and measuring things like crankcase vacuum, fuel pressure etc.
Also search this forum for ideas etc.
Fuel pressure is fine and the coil packs were split so needed changing , plugs were due also . The valve was also failing , and immobiliser had a random not starting issue , all these things were due to be changed to be fair as the car had been sat for a couple of years . From what my mech is saying it�s occasional and will sit sometimes and run smooth as ,then out of the blue bog down
You checked the serpentine belt and all the accessories and things that run off it? maybe one of the items has a problem and is dragging the idle down?
I�ll mention it to him tomorrow. He also mentioned that it was hunting when I last spoke to him ! I�m just hoping for a quick fix to be honest I�d pay anything at the moment to get it back healthy , driving me insane and him I believe
Are you in the UK? Your terminology makes me think British. Maybe someone can chime in with some reputable independent Porsche garages who can render a second opinion?
Yes bill uk ?? That obvious ha ha . Just seems so many dead ends and so many possibility�s which is difficult when not throwing any codes or cel lights . Air tested which rules that out .most things have been ruled out , im no mechanic but I am an engineer so understand how things work . But baffled by this as is my mech
I lived in East Molesey (worked in Woking) for a while
Do you have a Duramatric tool? Or, does your mechanic have access to a Porsche reader? Even without codes access to a good tool can tell you a lot while the engine is running.
Once again I�ll get on him tomorrow about it bill he is a Porsche specialist among others not exclusively Porsche but they deal with loads of them , so it�s not a random garage , so I�m hoping he will have all that is nessacery I know he has a relationship with our local porsche dealers aswell so I�m hoping he comes up with the answer soon if no one does on here
Denny, since you note you have a C4, your car should have received a Motronic 7.2 DME which is an early upgrade from the Motronic 5.2 which went in other early cars. This may be what your mechanic is referring with the exhaust sensors comment. Can you confirm which Motronic unit you received?
No, not much more elaboration. The information is coming from "The Definitive Guide"
Link to guide for your reference
Link to guide for your reference
The exact verbiage is:
"The Carrera 4 was also launched in the 99MY and while utilizing the same engine, the 4 had the benefit of the more sophisticated Motronic 7.2 engine management system. This allowed use of a new electronic throttle for improved engine control, also allowing the introduction of the superb Porsche Stability Management (PSM) stability system."
It is noted earlier in the chapter that 98 & 99 C2's got the 5.2, and MY2000 & after got the 7.8.
Think that what he was saying as he told me that at 2000 it changed !! So he thinks we possibly fitted a later one , which I understand would not work ! But when he is trying to find the correct one , no one seems to be able to help find the one we need as they all have the same part number and the breakers we have spoke to didn�t realise there was a difference so what I really need is a positive difference between the 2 . so hopefully your info will Help . So if anyone out there can tell me any number code difference that would be great , thanks all so far much appreciated
Ok so all good on which one is correct now thanks good stuff , next conundrum, is there a way of re programming the ecu we have ? I believe there is and by all accounts it�s only a 3 digit code we need to change to make it work , but finding the correct code is our problem , any help or ideas would be great
Hey Denny, I know you're UK based so forgive me for only being aware of USA based companies. There's a company on our side of the pond called ECU doctors. If nothing else, give them a shout and see what they can do for you. Lucky our big world gets smaller by the day and you'd definitely be able to mail your ECU over if this ends up being your only option.
http://www.ecudoctors.com/
