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Rough Starting 40th AE 996

Nedster

New member
Joined
1 Oct 2014
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3
HI guys, I am posting from Canada, just trying to see if anybody has had the same issue like i have with their 996. I have a 2004 40th AE, and have had issues with it starting pretty rough lately.

Dealer I bought it from looked at it but couldn't find what is wrong with it. They want to wait for the engine light to come on before diagnosing :dont know: I got a little video that shows what's going on. This is as bad is at get's usually it doesn't hunt that long, but it is what happens every time the car sits for a day or two.

http://www.youtube.com/watch?v=Go6KYA4_otQ

Ones it settles at about 1100RPM it will sit there for a minute or two until it warms up, drop down to 750RPM and run like a charm after that. Pulls strong, and starts without any issues while at temperature. If you experienced this before or have seen it somewhere i could use some ideas as to what it might be. Dealer apparently checked for vacuum leaks and compression, it was all good. I did have a topic open a while back on Rennlist about it but without the actual video.

http://rennlist.com/forums/996-forum/761203-rough-idle-help-my-local-dealer.html

I also did a bit of data logging with Durametric software at startup, but it all at least, seems fine.
 

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Can you work out when the coil packs were changed?

You could have one or more that due to weathering/tiredness are effected by conditions. After some current has run through perhaps they behave themselves.
 
Yes, about 3 months ago i put in new plugs and coils. It was doing the same on the old ones as well.
 
I'm no expert but sounds like it's not getting correct amount of fuel or correct air/fuel mix to suit when its cold idling. Almost like not having the choke pulled out enough in one of my old classics (for those of you who remember such arcane things) If I leave my car to sit and warm up before driving off I know my engine note/revs etc changes as engine warms up - within the ECU system there are different modes (open and closed loops I think I remember hearing somewhere) which change as it senses temp rising - maybe something in there is amiss. Would suspect a local independent specialist would be able to plug it in an diagnose sensor failures etc, surely??

Just a fellow 40th AE owner trying to help but happy to admit not being any sort of expert. Hope you get it sorted.
 
It does seem like it's starting in a closed loop for some reason. The only thing that can trigger that is the faulty coolant temp sensor. If the car thinks it is a t temp and starts reading info from the O2 sensors which are cold and not working. I have a replacement temp. sensor on the way as it is only $26. The dealer apparently checked the compression and for vaccuum leaks and said it all checked out. Although i am not sure if i can trust them. They think my flywheel is causing this issue :roll:. The other theory some guys are throwing around is leaky injectors which could be very possible as there was already a 996 in the area that had the same issue resolved with new injectors.
 

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