misfire at 4000rpm

I've just bought a 1998 996 (3.4) from a leading independent specialist. It had a full inspection and service before I picked it up (and they did spend some money on it (new discs and pads, air con condensor etc). However: I've noticed that intermitently there's a stutter in performance, accelerating hard, just as it passes through 4000 revs. Is this just one of those things, or dirty petrol, or is it something I should get checked out?

I've had my 996 (3.4) C4 for 6 months and covered the full rev range. It has never been anything but smooth, no hesitation. I think you should have your car looked at. Do you have any warranty cover from the dealer ? Hope it's nothing serious. Will

Mike - regardless if you got a warranty or not - if you bought from ANY sort of car dealer you get a months full warranty - law I believe, so get them to sort it pronto.

Coil or air mass sensor -get the dealer to sort it..... Mel

Mike, No help I know but mine does the same ! I am waiting for porsche to sort it under warranty along with the cam cover gasket replacement on my 98 C2. Please post when you find out what the problem is for sure or call me on 07710 -960695 Many thanks Paul

I've got it booked in now for 24th May. I'll let you know what they say. Thanks.

Mine for the 26th .............

Typically over the last couple weeks the problem's faded, but it still seems to be having odd misfires and flat patches. I took it in today; the diagnostics hadn't logged any faults, there was a loose clip on one of the spark plugs, but this didn't seem to make much difference. The next stage is to try it with a new air mass sensor - but they didn't have one in today so I'll take it back probably next week.

Thanks Mike, mine goes in tommorow and no doubt they wont be able to sort it either or it wont do it, the car just seems so slugish after about 4000 rpm. Im not sure where the air mass sensor is, but if it is the lead that plugs in just before the inlet butterfly i did pull it off on Sunday cleaned it (only the lead) and put it back on again, seemed to make a difference but maybe I imagined it, sometimes you drive the car and think ... wow, and other times you wonder what all the fuss is about, like I say slugish. I have only driven a newer 3.6 01 996 to compare but it seemed so much quicker everywhere. Will let you know Regards Paul

I noticed in June's edition of Porsche Post that the 996 Registrar ( I think his name is McGirl ) seems to have bought a brand new 996 which comes with a switchable sports exhuast. Does anyone know anything about this type of exhuast ? Having put a deposit on it last week, I collect my new (to me) 996 Cab Tip this Friday. Can anyone tell me if the toolkit issued by Porsche when the car was new is likely to have any specific or unusual tools in it that might only be relevant to the 996, especially the Cab version. I ask this since my 964 Cab had a weird tool for raising and lowering the hood if the power failed. Steve.

Steve, the porsche sports exhaust is a factory option but can be retro fitted at aything up to £1500, the sound though is superb !! I am currently in the process of modifying the standard system to sport specification but this will not be switchable like the factory item, I am nearly ready to offer these on an exchange basis to other club members for sensible money, if your bored with the washing machine sound of your 996 give me a shout. Regards Paul

Thanks, Paul me old mate, for your offer on a sports exhaust, but as I understand it, my 996(which I have yet to collect) has one already. How can I be sure, do you think ? The other thing that puzzles me about the Sports exhaust on the new car bought by Mr.McGirl, is tha he describes it as being"switchable". Do you think that this means it can be on or off depending, say, if one is putting it in for an MOT, or whatever ! The other thing I'd like to check out is that my 996 is described as being an 'S' model 996 Cab Tip C2. Does anyone know what the **** an 'S' model is ? Cheers, Steve.

Paul - tell us more about what you have in mind. Steve - I think he means 'S' registration ....

Mike finnally found out what the problem with mine is, it's the variocam sender unit not working, hence it never really gets on the cam just goes flat at 4000 rpm instead of ballistic !! get them to check it out for you on the diagnostic machine and make surethey rev it to 5000 or it wont pick up the problem by just pluging it in. Course they havent cured it cos they havent got the bits in stock !! no suprise there eh, still they only had it 3 days !!!. Steve, the switschable system you refer to is as it says switchable, you have a switch on the centre console that opens and closes a valve in the exhaust so you can have it as open sports type system or zanussi washing machine replica like standard, it's superb mate, well done. S refers to Tiptronic S which means the controls for changing gear are on the steering wheel, It's not relevant anymore to my knowledge as they all have touch change on the wheel, it goes back to the 993 days when the early cars only had the tiptronic control via the gearstick. Tim can you call me on 07710-960 695 and I can explain, I dont want to post details here for a week or so but please call me. Regards Paul

Finally got to try it today with the new air mass sensor; I think it's sorted the problem [ ]. Taking it down to Brighton for a few days so will get a few good runs, but so far it seems much smoother - can never be sure with intermitent problems - time will tell.

Mike, It is six months of protection under the Sale of Goods Act in which the burden is on the dealer to prove the vehicle is fit for the use it was sold to you for and they, the dealer, has to either take back the vehicle or you can demand that the vehicle is repaired. Check out this link on the autotrader website http://www.autotrader.co.uk/CARS/buy/ba/ba-8.jsp

It gets better, the car went in last week Thursday and Friday, had a call from the service Manager to say all done and the car now goes like a rocket !! Finished work early picked the car up and pulling away from the dealership you could tell that the car was still not right, floored it to find the car would not pull beyond 4000 rpm, called the dealer to ask if they had done anything to the car as it was the same as it went in !! Took car in again today to find that the other variocam sender had failed on the other bank of cylinders, not in stock so have to wait another day for parts see what happens next ..........

What a saga! Hope it gets sorted. Mine seems basically sorted although I still think it stutters sometimes. It also seems inconsistent, sometimes pulling better than others. Fed up with it now though, I'll take it back if it worsens, cos I suspect I'm just been neurotic now. Got booked in for a trackday at Silverstone soon, so that hopefully will give a chance to test it against other 996s -- although I'm afraid everyone will be storming past me whatever. I have noticed that having now had it a couple months, it doesn't seem quick anymore, I've even been checking in gear acceleration times against road tests to reassure myself, but basically , despite the above, it seems in the right ball park, I guess you just acclimatise. Maybe I need to drive something "normal" to remind myself what that feels like, bloody slow probably. Hope it's not the beginning of a slippery slope - performance mods, GT3, Turbo, looking for that "oh my God ' feeling to come back. Still gives a major buzz round the bends though, the only limit is my courage - I guess Silverstone should be awesome.

Well they have had it 4 days so far .......... Theve now managed to stap off three of the exhaust manifold studs, can happen I suppose but now we need an engineering firm to remove them ! Should be back tuesday, another missed weekend. Sooner those SL55 prices drop the better ........................ Will let you know Paul

Tispkj You wouldn't want an SL55, too must power for you 996 boys...oh and then there's the quality and equipement......nappa leather comfort massaging and air conditioned seats etc...... lee Anyway I told you..get shot of the unreliable old nail and treat yourself to an appreciating asset...993 or a 964 RS...(blimey I sound like Des)

Yeah, and only 34k more ............. bargain ! I could buy an unrealiable 996 for work and an RS for the weekends.

Why not buy a jaguar xk8 or R ?. Todays times says jags are now better and more reliablke than Mercs.

Tiskev Now you've confirmed it for me ...You have lost... you've gone totally mad....Jaguar?...Get the pipe and slippers man... lee

Well, it's back and appears to have the full 300 horse's that it came with originally. Both variocam sensors have been replaced and the oil leak from the cam covers fixed. However they did forget to reset the engine management system so I now have the motor warning light on on the dash all the time, they promise to reset it tommorow for me. Regards Paul

At risk of this becoming the moaning and wingeing thread.... My problem now seems to have moved in the rev range. Whereas before, at its best, there was a noticable surge in power from 5000 revs, today above about 5500 the power is just fading away. it gets to the red line but feels really breathless. I guess it's got to go back ... just hope this then leads to a fix as at least it wasn't so intermittent , and that it isn't a new and unrelated problem. I wonder about the variocam sensor thing?

Continuing on the theme of this being the moaning and whingeing thread, those of you who asked me to update them after my horrendous experience at an OPC earlier this month when they threatened to call the police if I continued to complain about crap service- well, this is the latest development :- I received a letter this morning from their Dealer Principal. It complained a full apology which completely vindicates my complaint. They ask for nothing more than a chance to put the problem right and have agreed to waive ALL charges for whatever work is needed. Well, that's a start, ain't it ! Cheers, Steve.

Mike, sounds just like mine did but mine was at about 4000 ish, would suggest that you get them to test the variocam sensors and or the air mass sensor, I note that you bought it from an independant, have they got the testing equipment to test this out ? also I was lucky that mine was from an OPC so had a decent warranty, the cost of these was 1400 pounds !! not sure if this was for one or the pair so make sure they dont muck you about till the car is out of warranty .......... Took mine back to reset the management system today and it seemed ok, got home turned the car off for an hour or so and when starting it again the light come on !!! ........ back again next week I suppose, still when you only pay 90 quid an hour I suppose you shouldnt expect to much ........ Regards

My car also 'goes flat' at about 5600, unless I have the throttle on the floor (Sarah says, "how do you know there's a problem, then?"). This is only really a problem at 130 plus in top, solved by snicking down to 5th, and so I have not bothered my independent supplier. Yet. I thought I may be suffering from that good old, 'they all do that, guv' syndrome, but get the feeling this may not be the case. I am also suspicious that the exact RPM coincides with the 'resonance do-dah, thing-a-me-jig' doing its thang. Anyone else experienced this?

Back in yesterday so another 3 days without it !! ....... and the best thing is after pluging it in they cant find out what is wrong with it !!! Anyone got a cheap SL55 for sale ?? ............

Four days and counting this week so far ................. Latest diagnosis is that it is one of the variocam senders that they replaced last week. Still no answer on the good will claim for the RMS. Regards Paul

So then 2 weeks and we are down to over fueling in a big way !! had to get the settings from the factory to reset the ECU ......... They did that and now need the car cold so they can test cold start up as this is over fueling as well......... Sorted that but cant find out why its over fueling, possible faulty injectors, checked them, now waiting for more help from the factory ....... Oh and regarding the RMS goodwill claim, Sorry sir not coverd !!!, I am going to speak to Porsche UK customer care myself and see if I can persuade them otherwise, so far this year they seem to have the car more than me ........

I like the car but after 3 new boxsters with no problems what so ever I am begining to wonder if I havent dropped a major clanger !!! Only good side to this is that I am not paying for anyof it and only use the car at weekends, if it was my daily transport I think I would have gone mad by now !! Paul

Still no car they are replacing the ECU tommorow ..................... What do you think the chances are for the weekend ??? Paul

Guess what boys ................. They sent the wrong ECU today. another one coming in the morning !!!

No different to the old one ............ They are awaiting factory assistance / Porsche GB. Have today taken this issue and the refusal to replace the RMS under warranty to Porsche cars GB

Well another week bringing the total to 4 weeks tommorow that they have had the car. My OPC is unable to find the fault as of saturday morning and are now thinking in terms of either sending the car to PCGB in reading, or getting there top technician down for the day ...... Have again spoken to customer assistance who tell me they will look into the delay. Paul

STOP PRESS ............. They have found the problem, the camshaft timing has been out all this time, one tooth out of alignment on the sprocket, just enough to cause the overfueling on one cylinder bank. Should be ready for collection tommorow.

No idea why it took so long just a case of elimination I think. Anyway I got it back tonight and it seems very good,very smooth, and a fair bit quicker ! Porsche have agreed that because I was without the car for over a month they will replace the RMS even though it is not covered under the warranty I have so some good news at least. Anyone want to buy a well sorted 996 with all parts replaced ??? Not sure as you say what to do with my spare time now, still the internet bill should be a bit cheaper eh ........... Regards Paul