I don't have a way to really format the data nicely and make it available here but I checked a data log file I have from my Boxster and starting about around 73F the coolant temp climbs a deg. or 2 every few seconds while idling.

The only time the coolant temperature reads steady is once the engine has reached some level of warm. That is the engine has various levels of warm. Based on its load, small because it is just idling, and the ambient temperature (and starting temperature) the coolant temperature reaches some sort of temperature equilibrium, the coolant temperature flat lines a bit, for 10s of seconds.

The unchanging coolant temperature reading your data capture chart has looks wrong to me. Also, that after 2:08 of idling the engine coolant temperature is just 37.5 after starting out at 21.8 looks wrong too.

That the temperature reaches 96 is as I would expect. The engine is warmed up. In fact 204F warmed up.

The abnormal behavior you are asking about only occurs from a cold start and is not present once the engine is warm nor is it present upon a warm start.

Thus if you are going to capture data that helps you ID what is going on you should strive to capture data from the initial cold engine start and keep capturing until the behavior goes away if you can capture that much data.

 

A couple of new developments: on daily basis, total misfire on all 6, and my fuel consumption has gone up noticeably. I think my MAF may not be working properly. I have a new one on order as well as the eng. temp. switch.

 

Misfires on all 6 cylinders is certainly an interesting development. Fuel consumption gong up? Not so much. My guess is the fuel consumption is poor because of the way you have been driving the car.

I would take care of the misfires then take a close look at fuel consumption (or any abnormal behavior) once misfires are taken care of.

'course the question is what is at the root cause of the misfires? While I have come across at least one report of MAF caused misfires (and I believe the poster) this is a rare cause.

But you have ordered the new MAF so I hope it proves to be the cure.

 

If the misfires were constant on a couple of cylinders then i would think, like suggested before, that it is the leaky injectors, or if it's one bank it could be part of the variocam system, but Total Misfire and increased fuel consumption high probability MAF is either bad, or confused (vacuum leak). We'll see.

 

For all cylinders to be misfiring doesn't require all 6 injectors be bad. Just two, one per bank. The DME dials back the fuel to address an overly rich mixture due to a leaking injector and the cylinders with good injectors misfire because they are too lean along with the too rich cylinder with the bad injector.

There is the possibility that just one bank has a problem injector and the other bank is misfiring due to the other bank's troubles. A misfire just means the DME detected an under (or over) performing cylinder. The cylinder's power stroke does not spin the crank and flywheel hard enough, doesn't impart enough acceleration to the flywheel and if this happens too many times over a span of time the DME flags this as a misfire. If one bank of the engine is running poorly the other healthy bank might develop sympathetic misfires, well, misfires caused by the upset from the other bank. We know at some point cylinders can help one another -- that is the purpose for the resonance flap in the intake -- so there has to be circumstances abnormal to be sure, during which they can negatively affect one another.

There is also the possibility the misfires are due to a bad flywheel. This is a rather rare condition (about as rare as all cylinders misfiring due to a bad MAF) but it comes up once in a while. If the dual mass feature has failed enough this can allow the flywheel to have excessive and inappropriate movement. The DME can't distinguish between the lack or or the excess of acceleration imparted to the flywheel by a weak cylinder or by a flywheel that has play.

But see what the new MAF does. What you learn after you bolt this on will help you decide what your next move should be, if there is a next move. The new MAF might be the cure. I hope it is. The intake air temperature readings you posted some few posts back sort of makes me like the MAF for this.