TravisB

Could be with thermal expansion/contraction there's a leak that flies under the radar except at extreme cold temperatures. FWIW though, mine does (did?) this too though, but not every time, and not quite as long as that..

Cactus

I was thinking about replacing the O2 sensor anyway so I will also clean the MAF.

993/907

Very normal in my opinion.
My 95 starts like that when cold, has since new.

The colder it is, the longer the hunt cycle. Mine will go about 10 sec longer than yours when below zero F.

Gordo

Ocean Blue C2S

My 1974 Carrera used to do that too, so it is not a 993 type only problem...

Bert

DJF1

Garage queens! LOL

my 993 AND my 928 do that. My old 993 used to do that as well...

abiazis

My 95 has done since new when colder than 32 degrees or so and settles into smooth idle pretty quickly.........

Cactus

I might be crazy but it is kind of cool. The wifey was stink eyeing me as she came out of the garage and asked me when I was going to fix it......

AOW162435

Just tell her it's "all motor".


Andreas

axl911

It's not normal. My stock 95 (and in with vram) doesn't do this.

With the SC and ltw flywheel, it used to do this but I've since fixed it with finding and fixing vacuum leaks and adjusting the ISV.

ETW

Mine doesn't do this but I just went out and checked the ISV anyways. It was filthy and the valve could barely move. All cleaned up now and moving freely. Will see if it makes any difference next cold start.

geolab

Unplug the O2 sensor, nothing changes.
MAF either works 100% or Zero, no in betweens, dirty or not
ISV should only be cleaned with WD40 or the likes. Cleaner and lube at the same time. Never brake cleaner, citrus cleaner etc. Make sure butterfly inside wiggles - rotates freely.
When there is humidity in the paper filter, the rpm's oscillate like this.

Cold start, where the whole car is in the cold.
After power washing engine
Long fast driving in heavy rain.
Regards

911-TOUR

Is the clutch depressed or not? 95 should be OBD 1 - one o2 sensor, and if it's bad check engine light will illuminate. MAF is all or nothing. ISV or vacuum leak is my guess. My 95 doesn't do this, but I have a Steve W. chip.

ryano

Mine does this as well only when it is very cold. In fact did it this morning when I started it up. I always thought it was normal? It finds the right RPM in about 20 secs.

JasonAndreas

On startup there is some extra fuel enrichment that is controlled by the CHT sensor which after ~20 seconds signals the DME to stop dumping extra fuel into the intake and to start paying attention to the O2 sensor. The hunting idle on startup is not unusual at all, its just more pronounced the colder the air temperature (you should only see this when the air temp is below freezing).

mongrelcat

My car hunts a bit when it's cold as well. Probably anything below about 40F.