996 Starting problem

I recently bought a 2002 996 and it runs great but the other day after stalling it it did not want to start. When I turned the key it just fired for a second or so roughly then died again. I called the RAC but by the time they came I went to it and it started fine and the car had no fault codes stored. He reckons it could have been flooded....could this be??? And on the way home yesterday after work it started fine and ran fine but I stopped off at a shop for about a minute and when I went to start it again it was the same, just fired up like on 3 or 4 cylinders then died. I left it for half an hour then I got it going. Does anyone have any ideas before I put it in the garage as it's strange as it starts first time from cold and only does this intermitently. Thanks Matt

Sounds like 'monday morning syndrome' to me- for reasons I can't recall (something to do with Lambda sensors whatever they are overcompensating and causing the engine to flood) you should make sure that when you start your car from cold, you get some heat into it before switching off again. i.e. leave it idling for a bit til there's a reasonable reading on the water temp. Called 'monday morning syndrome' because of when one starts the car, reverses it out of the garage to wash it on sunday, then find it won't start on monday morning! If it happens again, try this- floor the accelerator, and keep it floored while you are cranking the engine over on the starter. You will hear the engine begin to catch after a bit, but keep it floored until it starts. Then its up to you to back off again to not over-rev the cold engine, but not too much or it stalls and you are back to square one!

Thanks, hopefully I won't need to do it and it will be fine, if it does it again I'll try it.

....just went out in it again and it started perfectly from cold but when I stopped and restarted it after 5 mins it fired then spluttered then died. Did what you said, floored it and then cranked her and she went with a mighty roar! Do I need a new Lamba sensor then??????

Hmmm. How long had you driven the car before you switched off? If you'd been driving it for 5 mins before you switched off I'd get it booked in to the dealer as it should be quite warm by then.

been driving it about 10 mins I guess...........

Sounds odd then- get it looked at, could be the MAF or coils on the way out, usual 996 suspects. Or just maybe some dodgy fuel- I had this once with a Jag XKR- once the fuel had gone and I got a fresh tank of super, it was fine.

Agree with Robert. My first thought was MAF or coil packs. The coil packs can corrode after a period of time and become quite unpredictable.

Might be wrong here but methinks no mfr uses a Lambda sensor on startup, rather they start engines open loop. Reasons.... The Lambda sensor is about useless until it gets up to 600 or 700F. Normally, Lambdas start reading at 800F. Secondly, so much extra fuel is needed for cold start that a narrow band O-2 would be overrange. Even a wideband would be out of it's range and probably rendered useless from raw fuel droplets. The problem definitely sounds like a lean startup mixture. What you're describing is a classic lean condition. Not likely that it's coilpacks or anything ignition, based on your description that it fires briefly than stalls. Could be a dirty MAF. Less than actual air sensed can trick the computer into trimming the fuel. Flooring it would give more air and thus, enough fuel to keep running it's first (and most critical) few seconds.

At last I know what a lambda sensor does!

If it is a case of cleaning the MAF, I have heard it said that it is worth stripping everything from the inlet manifolds back to the air filter and cleaning all of the bits with carb cleaner. When you think about it, it does make sense.