plumbum

Recently my 1989 S2 starts idles rough and often stalls. I have owned the car for 7 years and never has this issue. If I give it a little gas it settles perfect. I have no other drivability issues, no smoke on start up and this only happens on the first start of the day.

Any common issues or ideas where I can start to look?

MAGK944

If it only happens on start up at idle and goes away when it’s warmed up or you give it gas then it’s classic Idle Control Valve (ICV) symptoms. You can test it to confirm by bypassing and the replacement instructions are <here>.

plumbum

That procedure doesn’t cover the S2 but I will look up on testing the ICV or system.

My old 951 had a bad ICV which caused a rough idle until warm. My idle is fine after a couple of seconds if I give it a little gas on start up.

dr914

fuel injection temp sensor, intake leak, idle control valve. sometimes an engine mount that is going bad causes vibration at lower rpms as well

thomasmryan

how's your battery voltage during the process? does the car 'wake up' when the alternator kicks in?

Jfrahm

could also be a stuck fuel injector.

plumbum

Mounts are less than a year old (factory Porsche) I would think an intake leak would cause issues all the time. Defiantly could be a temp sensor but it is dad’s that it only does it for such a short period?

plumbum

Battery is strong and alternator is less than 2 years old

plumbum

I was wondering about that however would it not cause some smoke?

jimbo1111

Have you checked your fuel pressure. Maybe some fuel related parts are going. Like filter, FPR. Sounds like maybe the system isn't producing enough fuel quickly enough.

Jfrahm

Injectors can stick closed as well as open.

No Lag

Try the fuel damper. I didn’t think it smoked on start up, but after someone else was starting the car I did see some smoke. Too rich. Damper had failed and was dumping too much fuel directly into the intake. After a 20 sec rough start it ran fine.
easy check. Unplug the vacuum line and see if any fuel drips out. Mine did. I temporary plugged it and the car started right away.
in the picture you can see gas dripping.