regrossman

First, the car has new spark plugs, 1 bar tune from Kevin at UMW, new 997 coil-packs, new O2 sensors, new MAF. Stock diverter valves, 52k miles.

1) When the engine is not up-to temp (180+), when shifting, there is a slight hesitation unless I shift a little slower then normal. This goes away completely when warmed up. I changed all the above in an attempt to fix this as recommended by Kevin but it continues. I have just been adjusting my shifting but would like to figure it out. Not sure if I can data-log anything with the Durametric during shifts ti find the problem.

2) When warmed up and I come to a stop, the voltage & idle will for an instant dip down to like mid 12s then bounce immediately back up-to high 13s where it stays. It only does this once of twice when driving over a course of maybe 30+ stops.

Boost holds a steady 1 bar and car runs great, no CEL or codes being tripped.

Macster

You have replaced the usual suspected hardware.

When did this behavior appear?

With no error codes, no other symptoms/behavior to go on that what you've observed/experienced and reported...

Have you had someone experienced with these cars give it a test drive to get his input? Maybe you are magnifying the degree of symptoms?

IOWs, maybe the behavior falls into the normal range of behavior? My cars get some idle time -- until the secondary air injection pump shuts down on the Boxster or until the Turbo's idle speed (elevated at cold start) drops to near normal idle speed -- before I drive them off because I have found the engines more tractable -- not that they are intractable when driven cold, without the behefit of this or really any meaningful warmup -- when given some time to build up a bit of heat.

The only other thing I can think of is the coolant temp sensor is reporting the temperature higher than it really is and the DME is not providing a rich enough mixture with the engine cold.

With an OBD2 code reader/data viewer you can look at the coolant temp prior to engine start, and compare it to the intake air temp, outside temp.

Then at engine start and thereafter you can watch it to see if the temp starts out ok but after a moment jumps or otherwise shows abnormal behavior.

Or you'll have to hook up the Durametric and have a friend drive the car while you drive the Durametric or you drive the car while the friend drives the Durametric and see what you can see.

Sincerely,

Macster.

Kevin

What are the RPM ranges that we are talking about. Please realize that you have two mechanical events that happen off idle. One being the low lift high lift camshaft/inlet tappet that will vary depending on your engine load request, temp and engien RPM. The second BUMP is the vario cam rotating and changing your camshaft timing> the module will rotate the camshaft to vary the advance depending on load request, temp and throttle position. The ECU want's to give you maximum torque, however it is restrained by engine operating temperatures. Think of it as a governor.

This engine platform is not as smooth as a fixed camshaft engine, however it is smoother vs other Variable camshaft engine manufactured by other makes.

regrossman

These 2 issues have happened for the past 10k miles (since I bought the car). Factory tune and Kevin's tune both had the same behavior. It happens at all RPMS when cold but seems worse if the RPMs are higher because the hesitation feels more violent from the revs dropping during the shift. The only way I can avoid it is to shift, then wait a half sec before giving the car gas. Once I hit 180, I drive it like normal. With no codes this is a pain to diagnose.

I haven't had anyone drive the car or get any other input. The car runs fine after warmed up but I figured maybe someone else might have had these issues and I could find an easy fix.