engine light on and engine cuts out

new problem with my 2001 996. 3.4 had the codes read, p0410 & p1411. both to do with secondary air system. seems to happen when warm after approx 15 miles, light on engine cuts out. allow to cool and restarts again. anyone shed any light on where to start? help appreciated

You could start with this: https://www.youtube.com/watch?time_continue=28&v=go34DJAuPyg Its for a boxtser, but mechanically they are extremely close to a 996. It sounds like your problem is related to something to do with the cold start system. Despite the codes, I would also not discount the crank position sensor. Can you be more descriptive about the symptoms? Does it cut out when you come off the throttle when it is warm or does it cut out even at driving revs (say 3000+)? How long does it need to cool down before it will start again? Have you tried restarting it when it's still hot but with the throttle open? Do you have an Egas throttle or a cable throttle?

hi, starts perfectly ok when cold, once its completely hot, roughly about 15 miles, starts to jerk a bit, when you come off the throttle just cuts out. will not start, just turns over. leave for approx 1 hour and it will start ok and run until it gets hot again. tried starting with the throttle wide open, turns over but does not fire at all, when the symptom is present. not sure what throttle set up i have. is there an easy way to tell? thanks for your info cheers george

Have a look at the throttle body where the big black rubber inlet trunk goes in. On the right hand side you will see a metal cable wrapping around a black doobry that you can rotate by hand. If you don't have that, you have an Egas car, which is essentially and electronic throttle rather than a mechanical one. Are there any other codes? If it weren't for the codes you've mentioned already, based on the symptoms alone I would be suspecting the crankshaft position sensor.

Also, the reason I asked if it will start with the throttle partly open, is that a car with an air leak in the inlet manifold is much less sensitive to that leak if the throttle is open, whereas a car with a duff crankshaft position sensor won't run at all no matter what the throttle position if the sensor has gone into it's duff mode. - i.e. one of the failure modes of the sensor is they heat up and then give a voltage reading to the ECU that is outside the expected range, and so for safety's sake the ECU cuts the ignition to the engine.

It certainly does sound very similar to a heat soak issue on a dodgy crank sensor - for some reason they often don't throw codes either. On the positive side they are relatively cheap and easy to swap as long as they aren't seized in.

hi. thanks for the reply's, yes there was 2 other codes, but the tester chap told me to ignore them. P1579 REFERENCE MARK SENSOR SIGNAL IMPLAUSIBLE P0336 RPM INPUT CIRCUIT NO SIGNAL Hope that makes more sense. any advice on where to get a replacement. or where abouts it is on the engine, as i dont have a clue. anyway, i'm of to have a look thanks again george

Definitely the crankshaft position sensor then. Part number 98660611202 Get a Bosch one rather than a Porsche one. Its half the money for the same part. Design911 sell them. https://www.design911.co.uk/fu/pt25...L-1997-08-01/Speed---Reference-Knock-Sensors/ You'll find it on the front left hand side(passenger side) of the engine about half way up. Do some googling and you'll find some pictures of where it's located. It measures the speed of the flywheel.

Also, if you're handy enough with the spanners to do things like change your own brake pads, then you're handy enough to change the sensor. If you're not then a garage shouldn't take longer than 30 minutes to do it for you, it's really very simple and there isn't much that can go wrong.

ok, thanks i have ordered one and will have a go. update you when hopefully sorted. thanks very much george

Hi Martin, I agree with everything you say on this as I had a Position Sensor fail on me a few years ago. I went for a Bosch part and has been fine ever since. Being pedantic I don't agree that the sensor measures the speed of the flywheel only. In this case, the position of the flywheel is important to deduce piston position and hence the timing of the spark and I believe the fuel injection (though I could be wrong on the FI issue!) As you say, the pulses per minute will register RPM. To replace the sensor, I gave it a good dose of penetrating oil on a few occasions the days before to help release it. Also, you need small hands to connect the multi-plug!!

Thanks, yes I was dumbing down a little. To be precise, it measures not only the position but also the speed. Position being necessary for ignition timing and speed being necessary for a host of other things such as input to the injection map, rpm guage, variocam cutin/cutout. There's probably more to the list as well.

Yes, pretty fundamental for the car to run!! :thumb:

CPS measures speed of rotation which is essential for misfire recognition and the flywheel has a missing tooth at TDC so the CPS then knows the TDC position. Cam sensor / sensors then work out TDC on No.1. Poor hot start .. or many spins over before fireing are usually CPS or on early cars Cam sensor .. later cars have x2 cam sensors so its unlikely for both to fail as Bank 2 whilst its purpose is camshaft vario cam monitoring can also be used as a backup for TDC recognition if bank 1 cam sensor fails .

Update on this Received a new bosch sensor. fitted Monday. totally agree, very tricky to fit but got there in the end. Have done about 100 miles since and all seems fine. A big thanks for all your help, much appreciated Regards George