Hello everyone,
I am chasing misfire (pending codes) on my 997 C2 (110,000km).
Only on cold start (car not driven for a few days), pending codes for misfire (P0300, P0301, P0302 & P0306). If I cut the engine when it is warm and start it again after 2 minutes (still warm), the pending codes disappear. No Cel. The Cel only appear when I drive the car (which has sat for a few days) only once and don't start it again for a few days. 3 cycles like this and the Cel usually appear (but not flashing). The car runs fine, nothing wrong.
I have changed coils, spark plugs, made vaccum leaks tests, injectors cleaned (by pression not removed).
What could be next? Variocam solenoid bracket?
Thanks a lot in advance!

 

Sounds like it's only an issue at cold start so I think you need to limit your investigating to temp related items. The DME takes it's intake air temp reading from the MAF so I would disconnect that and start the car cold to see if it behaves any differently when it's running in the default generic map. If the MAF isn't communicating temp info to the DME then it won't enrich the mixture for cold start, which could result in misfires, like when a carbureted car without a choke coughs, pops, and sputters until it's warmed up. Also, when you start the car ate you getting the higher 1,100-1,200 rpm Dorcas bit until it drops to the warmed up 600 rpm idle speed. If not, this can point to the MAF also. Do you run an oiled air filter like a k&n - if so, get done MAF specific cleaner and follow the directions on the can. A coating of oil on the MAF wore will effect the readings to the DME. Also, the DME takes temperature input from the cooling system temp sensor to control a lot of things, like fuel trims, etc. I'd also look at that.

 

Thank you so much for your response. Yes, I get the higher 1,100-1,200 rpm until it drops to the warmed up 600 rpm idle speed. I already cleaned the MAF, could it be the MAF sensor? I'll try to disconnect it as you wrote. No K&N air filter. Where is located the cooling temp sensor and how can I test it?
Again, thank you!

 

Attached is a useful document I downloaded from Pelican Parts that shows all the sensor locations for the M96 & M97 motors.