Start up problem ?

[geather]

1999 Boxster 2.5 Tiptronic. My understanding is that on start up (especially when cold) there should be a brief (1-2 seconds) period of high engine revolutions to ? quickly raise oil pressure. This then settles down to the usual cold idle at about 1200 RPM. My 1999 Boxster does not do this. It starts easily but the initial idle is rough at about 600 RPM for a second or so before it runs smoothly at 1200 RPM. The car otherwise performs flawlessly. Is this a fault or is this normal for the 1999 model year.

Geoff

[986Jim]

My 99 5spd does jump up at start then settle down as you described. I don't know how the tip works when it starts up but should be the same from that standpoint. I would wager to guess something is off.

Generally when there are problems like that it's because the computer is getting a funny reading from something like the IAT (intake air temperature) or MAF (Mass air flow) sensor which is combined on our cars. There are other reasons for variation thats just an example...

I'm sure somebody here has experienced this before and can chime in with some possibilities? Loren???

[Loren]

Your Boxster should idle at 750 RPM (Tiptronic - with AC off) and 800 RPM with the AC on. If your car idles higher chances are your Idle Control Valve is sticking and/or your throttle butterfly has a carbon buildup that needs to be cleaned.

My understanding is that on start up (especially when cold) there should be a brief (1-2 seconds) period of high engine revolutions to ? quickly raise oil pressure.

Not to my knowledge.

[geather]

Your Boxster should idle at 750 RPM (Tiptronic - with AC off) and 800 RPM with the AC on. If your car idles higher chances are your Idle Control Valve is sticking and/or your throttle butterfly has a carbon buildup that needs to be cleaned.

My understanding is that on start up (especially when cold) there should be a brief (1-2 seconds) period of high engine revolutions to ? quickly raise oil pressure.

Not to my knowledge.

Thanks for the info,

Cleaned the MAF, throttle body and idle valve. No change. The car idles at the corect RPM when hot or cold and when the AC is engaged. The 'problem' only occurs for that brief few seconds after start up. The jump in RPM does not occur before the car settles down to its normal idle

Any further thoughts?

ge

[Loren]

I would replace the Idle Control Valve.