996 starting problems! Help!!

I have had my 2002, 996 Carrera 4 for about a year now, not had any problems with the car at all, on Friday evening i travelled home from work as normal and parked the car in the drive. When going to use the car on Saturday morning it wouldn't start! The ignition key turns and it tries to fire up but once you let the key go it cuts out, even when applying the gas. Anyone got any ideas that may help me sort this problem out. Many thanks.

I noted Richard saying the ignition barrels can break up inside in another thread. I'm sure he'll be along in a minute but do you have a bunch of heavy keyrings on your keyfob? That is the normal cause for a failing ignition barel as they swing about as you drive.

Thanks, i do have fairly heavy keys on the fob! Something so small can cause that? I guess its a case of changing the barrel and see if that solves it! Otherwise could it be anything else? Many thanks

Liam! Is it cranking at normal speed? If so, it might not be the ignition switch. In the four years (or so) I owned my C2 I had a similar issue on two occasions, years apart, when it was like the engine had flooded. I had to crank it for ages before it would catch enough to continue running (or rather spluttering), and then it slowly cleared after about 15-20 seconds and burst into normal life. It didn't throw up any fault codes, nor did I ever find what was wrong. I recall just cranking it with a half-open throttle until it caught. Not much help, is it?

Thank you Richard. I basically turn the key, it fires, splutters like it is going to fire up and then dies! And will not go past that stage. [ ] It does not show any faults when run through the test.

Check the fuel pump is pumping the correct pressure. Had similar problem with my C2 a year ago and it proved to be a clogged fuel pump. New one fitted at OPC under warranty. Problem sorted.

coils????

Replaced the ignition switch, wasn't that! [ ] Fuel pump checked and seems fine, so probably not that [ ] No faults being shown on diagnosic test [ ] Had all new coils fitted 2 mths ago, as the previous ones had cracked. This all started when i had driven the car fairly hard on the way home and parked up. Then the next morning started having this problem.

Where can i find the fuel relay on the 996 C4? I can't find any data to show me which one of the relays it is! Can anyone point me in the right direction please?

The fuel pump relay is in position 13 on the relay board in the driver's footwell, above the fuse box. When you say 'checked fuel pump', can you hear it running constantly? When you turn the ignition on, you should hear it for a couple of seconds, and then it should go silent, as it is up to pressure. Was there any work done on the car in the preceeding 200 miles, which might have involved disconnecting the battery? If so, it might be that you have simply run out of fuel. Being a C4, if the battery is disconnected when it has less than 19 litres of fuel in the tank, when it is reconnected it will read higher than the actual fuel level. That being the case, try adding 5 litres of fuel.

Thanks Richard. The fuel pump does make a noise for a couple of seconds then goes silent, so not going constantly. The vehicle was filled with fuel a couple of days before it packed in and is registering over half a tank now. Also you can hear the fuel splashing about, was the first thing i ckecked so as not to make myself look a complete loon [ ]

Made a decision today, replaced fuel pump, ignition switch, fuel pump relay, still the same, won't start. So my love affair with Porsche is over and the car will be traded in for as much as they will give me. Had enough.

It hasnt taken much to put you off has it? Have you tried disconnecting the battery for a couple of mins with the key on the ignition setting (1st click before its turns over) it might reset any settings that are wrong.

It can be very annoying when a problem can't be solved but you need it working before you sell it unless you want to waste money, take it to a good specialist and I am sure the problem will be solved it could very simple. Good luck either way PJ

Chris, 2 weeks without a car has put me off!! I have tried everything people suggested and still nothing, battery has been disconnected today as was dead, new battery fitted and still nothing! Philippe i agree but seems like i am throwing good money after bad. The vehicle has been looked at by a good independant and he has given up as tried all he can, only option would be main dealer and can see that costing a small fortune that i dont have at the moment. Other suggestions are it could be the alarm/imb but have a feeling Porsche would have a field day with my bank account.

Find another indy. If it was the immobiliser, it wouldn't crank, the fuel pump wouldn't run, and there would be no spark at all.

Thats what i thought Richard, clutching at straws at the moment. Its pushing fuel through i can smell it after cranking for a while, but just doesnt want to give it that extra to start, its so frustrating!

If i take the fuel pump relay out it still does exactly the same as it does with it in position! Replaced it with a new one and makes no difference, does that sound right?

Odd. If you take out the fuel pump relay, I can't see how the pump can be running.

Telling me it's odd [ ] Just got it checked for faults again as i wasn't totally convinced by the first lot i was given, none!!! Codes showing are: P0103+ Mass air A circuit high input P0223+ Throttle position sensor B high P1120 ?? Cant read his writing P1138+ " " " " " " " " " P1190+ (could be P1140+, can't read his writing!) P2135+ Throttle position sensor switch A/B Anyone have any idea what my next step is? Or where the throttle position switch is located?

Is the throttle working? The butterfly will open when you press the throttle with the ignition switched on. Take off the inlet hose where it attaches to the throttle body, and you will see the butterfly. Drop me an email and I'll attach the diagnostic sheets to a reply. (In the morning).

Sorry to hear about this Liam. I am by no means no expert and Richard will probably tell you i am wrong but could it be anything to do with the variocam solenoid. ie Starting rough and then dying straight away. I had to replace this on my car as it turned over but wouldnt start. This is a real shot in the dark. Had to get an indie to do it though as it was a pig.

Would a faulty through up those codes?

The item common to almost all of those fault codes is the throttle position sensor on the pedal. Liam mailed me to say that the throttle isn't responding, but the AA man got it running temporarily by actuating the throttle by hand.

excellent news, keep the faith

Richard, where would i find the switch, and is it something i could replace myself or have to take to garage?

I sent you an email at 10 o'clock this morning with a diagram of the location of the throttle pedal potentiometer, and all the diagnostic sheets. Follow the cable from the top of the pedal, and you'll find it at the end, above the pedal box. As I said in my email, check the plug/socket connection first, as the potentiometers are mighty expensive (£450+VAT).

Ok thanks, Richard. I looked for email but couldnt find it, i will check again. Many thanks

Being picked up on a flatbed 2moro [ ],(always looks so wrong seeng such a beautful car on one of those!) then off to an Indy, will let you know the outcome. Thanks for all your help.

Hey Liam, Just read the full post. Good luck with everything. Let us know how you get on!!!!

It's at the indy and they don't know what's wrong! Either Throttle switch £60 or Sensor £450+ starting with the cheapest and working way through! I had to order the part mind you, thought the point of a garage was that they do the work to get the vehicle sorted then give me the bill, obviously not, i could have changed the throttle switch at home myself! This is crazy, how is it never simple!!

Sorry haven't read the full post as I am on my way out, but could be either fuel pressure, injectors not pulsing, incorrect timing / ignition relay, fuel relay / pump or TPS. The key is process of elimination - rule out fueling, rule out ignition you are left with electrics and visa versa. It will run and start with a faulty MAF, lambdas, crankshaft sensor, coil packs broken down (as not all will break down at the same time, will just run lumpy and fire on a few but still run), if your speed sensor is way out it won't fire up correcly. TPS won't pick up the throttle is open at all but should throw a fault, injectors probably won't throw a fault - I think the duty is measured through the ECU sending the signal not what they are actually doing. Anyway hope that helps......

What diagnostic equipment does this indy have? They should be able to read the throttle position sensor on the pedal. If it doesn't respond to pedal movement, it would indicate that the sensor isn't working, or there is a bad connection.

Not sure what they have, it is with Nick at Auto 2000 in Kempston, Beds.

Still without the car!!! Now been told it COULD be the throttle body! But they are not sure, only way to find out is to replace it, seems like another week without it min and still may not solve the problem. Wish i had gone to Porsche directly now, going nuts here. Not a happy bunny at all. [ ] Going round in @@@@@@@ circles.

Liam, Really feel for you at the moment. How much is a throttle body?

Honestly i really don't care how much it costs now, (£360.00 for throttle body apparently, and this may not solve the problem) just want it fixed and back on the road!!

Sorry I asked!!!! Hope you get it back quickly and you can start to enjoy it.

[ ] I have had Mercs, BM's etc, never been off the road for any period of time, first Porsche i have and its been a pain in the arse! [ ]

Sorry Liam its not good and I know how you feel. Don't let it put you off, you will fall back in love with it when you get her back, I promise. Porsche centres are great and they really know there onions. Wouldn't have anyone else look after mine. Ill say a prayer for you, good luckam sure it will all work out. Steve

potentiometers £450+ how can they get away with charging that for a large variable resistor?.

Not trying to justify Porsche's pricing structure, but it is a bit more involved than that. It is a two-channel encoder. It uses two channels to provide a degree of failsafe. Still bl**dy expensive though.

Id sooner fly by wire any day. Old skool for me. Anyone know if the 964 were still cable? Im guessing the 993's are not?.

964, 993, and early 996's were all cable throttle.

Thanks Richard for the info Im surprised at early 996. Up to what year? I maybe one of the lucky ones ?. @Liam any word yet?.

C2's up to MY2000 had cable throttle. Electronic throttle was necessary for PSM, so was introduced at the same time. All C4's have PSM, and are electronic throttle.

Guess that means most of us are slaves to binary geeks then in this modern society. DARN!.

Still no car, heard today that they have ruled out Throttle sensor and throttle body, also fuel pump and various other bits it could have been!! Now they think there is a wiring problem, one month on friday since i had my car!! [ ]

Right, wiring all ok. Problem is likely to be ECU! (or take a loan out as it's known!) Apparently they cost a few bob, and Porsche Germany and Uk have confirmd that it can't be repaired so a new one has to be found, only one in the country down in Reading! So they are going to use a donor and see if it is that, if so then they will have to get hold of the new one. [ ]

Update: It is not the DME, the donor vehicle was used and made no difference so that is a relief 'at the moment' financially. They now suspect there is a problem with the immobiliser, they have managed to get the car running by bypassing it and working it manually from the throttle but is running VERY rich and alot of fuel is coming through the exhaust! I wondered if this was because it has been cranked so many times without it actually starting and the fuel has been building up?

I don't see how it could be the immobiliser if it cranks, fires, and runs, albeit with manual throttle operation. If the throttle pedal sensor and throttle body have been ruled out it is sounding like it might be a wiring problem to me. I suspect you are right about unburned fuel in the exhaust.

Apparently the throttle sensor and body are ok, also wiring checked and ok! They are as confused as i am, they have never come across anything like it before and they have ruled most things out now. Very strange.

Might be some handy reading/ideas Here

Not all what it seems apparently! The wiring is now faulty, 4 wires going to the throttle body should show 5 volts? One is showing 9 1/2 volts, so they assume is faulty and are now stripping the wire ans tracing it back to reapir. This in turn has now damaged 'apparently' the ECU (DME)!! And this now needs to be repaired or replaced! Anyone know somewhere i can have the DME checked by and independant so i know they are being upfront with me. I am confused as they have said so many things, thursday it "Definately wasn't" the DME as the donor vehicles DME didnt work in my car either. Now the donor vehicle is failing to start when the put the DME back into it! And it is my car that has caused that DME to fail also. All i know it will be 6 weeks on friday since i had my car ans it's really F@@@@@@ me off.

Have you thought of taking it somewhere else? For an independant they don't seem to know what the problem is and they're just clutching at straws.

It's now been to three independents, local guy who works on Porsche, Auto 2000 Kempston & Templetons in Rushden the latter two are well known in the area for being able to deal with Porsche. I am now leaving it with them one last day and the it will be taken to Porsche at Towcester, expensive but i need the car running now to be able to sell it!

I thought you had already taken it to the OPC. From what you said on here and in emails and on the phone, I thought you had decided to do that. Judging by the changing diagnosis on a daily basis, I still think you should do that. If it is a wiring fault, as I suspect it might be, it is likely to be somewhere on the engine loom, between the throttle body and the main connectors on the right hand side of the engine compartment. From there they go to the DME internally, which are much easier to see, and much less likely to be damaged.

OPC towcester couldnt take it for a couple of weeks, then Templetons was recomended, Auto 200 coundnt fix it and i managed to get the car picked up from them and taken to Rushden where its been for the last ten days! They assured me they had all the systems in place to fix it, unfortunately it has taken longer than first thought. Porsche are now able to fit the vehicle in this week so if not fixed by 2moro then it should be with them by Wednesday. Once fixed i have a feeling it is time to move on and cut my losses, have a feeling this is jinxed [ ]

Right i need some advice please as i am being told one thing by Porsche and an ECU specialist and another by the garage. My ECU (DME) was taken out of my car and replaced with a donor ECU, this failed to solve the problem, then the donor vehicle failed to start when they put the ECU back in. They then purchased a second hand ECU for the Donor vehicle and this doesn't work! They are saying that my car has passed the fault to this donor vehicle! They told me this morning that they have the 'codes' for the ECU and it hasn't solved the problem and therefore proves my ECU is faulty and needs replacing although i have been told by Porsche and the ECU specialist that they would need to get them from Porsche themselves, as far as i can make out this hasn't been done. Porsche and the specialist also said that it is very very rare for the ECU to fail completely and need replacing. ECUS have said that from what i described it wasn't an ECU problem as have porsche but they both say now it could be as it will be confused and needs totally re programming. Although the original fault still needs to be found. The garaged have said that the fault in my car has 'spiked' my ECU and that of the donor vehicle! Is all this possible and who do i believe? Porsche have now confirmed that they can fit the vehicle in on Friday if need be and the garage that the car is at have said they will carry on working on it to try and fix the problem, he doesn't really want it going to Porsche as they haven't fixed the problem then how can they charge me, thats the impression i get. I know it will have to go to Porsche i just don't want to be lumbered with a bill from this garage IF they have done something wrong.

I understand that a fault in the wiring of your car could have damaged both your DME, and the DME of the donor vehicle when it was fitted to your car. However, I doubt that it could have damaged the wiring of the donor car when the DME was refitted. I would have thought it would blow a fuse rather than damage the wiring. So, I'm at a loss to see how the second hand DME fitted to the donor car could have failed. IMO, what needs doing is to check each of the 60+ wires connecting the DME to the engine sensors, actuators, and the throttle pedal, for a break or short to ground. It is likely to be a painstaking process, but the only way to find out where the problem lies before fitting a known good (or new) DME. Maybe re-programming your original DME might work in this case.

Fingers,legs, eyes crossed they may have found the problem! It seems the oxygen sensor attached to the exhaust has been damaged or "melted" and has fused together to create a live wire! the Ecu has been sent off for repair and they will begin to rewire the sensor and replace 2moro, and hopefully the ecu can be repaired in the meantime and i get my car back by the weekend...........If not i am going to find a very high bridge and push it off [ ]

Did they get the donor car running?

I understand your pain. I also Hate most Garages. If this were the case would your ecu not have been completely fried in the first place?. Rather than frying in there process of elimination by hardware swapping parts, until something works (or not). "that's not fault finding/diagnosis". None of the suggested faults they have found are remotely related (apart from throttle body & potentiometer) and they haven't succeeded in fixing anything. The bit about 5v at throttle body, I'm sorry but if this is fed from potentiometer surly that would be a variable voltage from 0-12v maybe Richard Knows the answer to this? I think there's probable cause for you to give them an invoice. I wish you all the best and hope your Car is well soon. Regards.

At last [ ] The car is repaired and ready for me to pick up on Monday, the wire from the Oxygen sensor had melted and spiked the ECU, sensor replaced and wire repaired, ECU was repairable so that's a godsend. Not been advised of cost yet but i'm beyond that now and just want my car back. Thankyou to everyone for the advice especially Richard.

What caused the wire to melt

Liam, So who were the 'stars' who finally diagnosed it correctly? Guess they're at least entitled to some forum publicity...... Glad it's finally sorted..... bar the costs! paul

Apparently the wire had been in contact with the exhaust and the heat had melted it! It was with Templetons at Rushden for over two weeks, finally they found the fault. I am happy it's be repaired and that they found it, time it took not so happy but i will have back in a few hours so.......[ ]

I know Dove House Motors used to use them to prep their cars but now have their own Service Dept, it may have taken longer than it should but congrats to them, hope the cost not too extortionate.....

£1220.01 [8|]

Ouch!! hope you keep it & enjoy.......

Likewise. Don't be too hasty to get rid. Try to put it behind you and start to enjoy it again.

Ditto Richard. Pleased it is fixed. Spend some time loving it. These things happen but why not visit cirnbury this Sunday? Get the polish out, promise you'll appreciate even more. Know I did when I got my boxster s back [ ]

Liam glad you got your Car back. Regards your invoice, Do you have a print out of the original Durametric fault codes?. DME was not dead when you first took the car to them so as far as fault finding goes it should have been the first thing they did. Surely that would have shown a code as the sensor would have had a complete short?.

Yes fault codes were pointing to Throttle sensor, air mass originally. They have given me the old Lambda sensor and you can see its burnt out. My only concern was the DME repair, i can't prove either way if this was damaged or not, i have to take their word for it. Still shes back and it felt good driving to work this morning, my better half said i was like a kid at Christmas the smile that was on my face when i picked it up [ ]

Cirnbury? Whats that?

I think they meant Cornbury

Yeah I did sorry. This blackberry, I dint know. Should have picked the I phone [ ]

Yeah Ill bet. I know that feeling.

Ah yes the mighty Iphone. Still, at least you can wait until your contract is due for renewal. The new one may even be out by then