DMB14

Hi everyone, I got an 85.5 944 n/a a little over a month ago and it's great. My first Porsche. It seems in great mechanical condition and the mechanic who works on it says the same.

Except, on a cold start the idle will drop to almost 500, the engine will start to chug and the revs will shoot up to 1300ish, then they will fall again and the cycle repeats for a few times. When the engine is warm it operates flawlessly. Is there anything wrong?

Zporsche944

mine does the exact same thing I think its normal but you should wait for somone else to chime in

DMB14

Good to know. It's not a big deal right now, but I'm just wondering what it's gonna do in winter on those 20 degree mornings when it actually is cold .

Pcar944

Dont know the answer to your question but congratulations on getting the car and welcome to rennlist.

Post Pics when you can!

Zporsche944

on the days its is cold... it just does the same thing but longer... just give it 2 minutes before you drive it then keep the revs under 3K till is warm... if you live in canada like me you will want to invest in a small magnetic heater to stick in the engine bay

KY944S

Sound somewhat like an ISV. Which can be cleaned and may work properly.
Welcome to the wolrd of 944 ownership

porscheEH!

It's probably your Engine temperature sensor, which controls your fuel/air mixture. When the engine is cold it sends a bad signal saying the engines actually hot and it will ether richen the engine to much or lean it to much i'm not sure which one, ether/or will make it Rev erratically. Then when the engine warms up the signal the sensor sends is good because the engine is warmed up.

DMB14

I'll take a look at the ISV in the morning.

I tried to upload pics of my car, but I can't because I don't have the minimum # of posts required.

Thanks for the input. I'll have the mechanic take a look at it next time I take it in. Sounds a bit over my head.

Oh and thanks for the warm welcome!

Sam944 N/A

I had the same problem... I cleaned the mass air flow sensor witch was blackened all the way through and that helped a bunch.

DMB14

Ok, I've located what I think is the ISV. There seems to be a slight crack in the tubing leading out of it which might be bad...

Could someone post a pic of where the ISV is so I know if I'm right? It would be much appreciated.

Chwatson

I had a somewhat similar problem when i got my car... Very simple fix.

Mine was the cold start sensor (not sure what the proper name is) and all you have to do is take a big screwdriver and hit it with a hammer, and it knocks all the crap off it. varnish builds up over time, and my porsche mechanic said just sock it once and it'll be fine for another 20 years.

Chwatson

PS don't hit it too hard

DMB14

Haha I'll try not too.

Where is this sensor located? I'm a bit of a noob when I get under the hood.

Chwatson

Problem was that my mechanic just said "hey, pop the hood"

I hear THUNK and he says "try and start it now" and it cranked up just fine even though it was cold.

I didn't really get a good look at where it is. I'll check next time I get a chance.

DMB14

Hm, well it sounds like a fix even I might be able to do!

Let me know if you find out where it is.