Aries9

My 1980 911SC starts up really rough. It sits a lot so I'm wondering if you think it's the gas. The car has no problems once it's warmed up and I've used the high revs for a bit. But when I first start it up it will stall unless I give it gas but it seems like the gas is on and off, pressing the gas doesn't instantly mean the revs will go up. They may, or they may not. It's very odd. I usually stall about 4 times until it can idle without stalling. Until I get the thing warm it does small backfires and the car lurches.

Do you think it's bad gas or a bad filter or what should I check first?

GothingNC

Might be an issue with control pressure and or the Warm up regualtor

http://forums.pelicanparts.com/porsc...em-911-sc.html

John

2specs

I kinda have the same issue but I don't get any backfire. On a cold start I pump the gas twice before starting and that seems to help. I don't touch it after that. It will idle about 500 and gradually build it's way up to 950 and then it's perfect from there. When I shut it down after a nice drive and start it up about a half hour later it will do the same thing, idle low and gradually build to 950 again and the engine is still quite warm when it does this. Warm up regulator is rebuilt. When I figure it out I'll post it but don't hold your breath, we bought another house... so much to do.

hamah

Similar issue here. Because my 91 C2 is using the Motronic DME I don't touch the gas. When she's cold she starts rough and likely won't start on 1st turn over like she used to. Once she turns over she runs rough (like missing a cylinder or so) for a brief moment and then runs smooth from there, still not having touched the pedal. This only happens when cold.

Ed Hughes

If your gas is more than 3 months old and you don't use Sta-bil, you should change it.

rusnak

Yup. Could also be a vacuum leak.
Yup.

2specs

Well in my case the gas is good, I have been using premium and gone through a few tanks already this year. I do plan on adding a fuel injection cleaner to a full tank of gas then change the oil after that tank.

If it was a vacuum leak shouldn't it run rough warm as well?

Ed Hughes

I've seen vacuum issues where it hurts the idle, but runs OK when the throttle is opened.

2specs

It idles perfect at 950 when warm.

rusnak

A vac leak would cause it to run lean. It may be that when the engine needs a richer mixture, it stumbles. But a lot of things can cause this, including the WUR, and even a weak fuel pump. You have to check fuel pressure in any case. If you had a afr gauge, that would be the next thing.

2specs

I did pick up a new fuel pump and planned to do that anyway. The one in the car is still working but suspect it's wearing down because it can be quite loud at times. I will try that first.

Thanks

Steve Weiner-Rennsport Systems

Your car is losing fuel pressure against the FD when the pump is off so if you change the check valve at the outlet of the fuel pump, you should be OK unless there are other issues (accumulator).

Naturally, I'm assuming that the fuel filter is nice & fresh,...

2specs

New Bosch pump has a check valve on it. I'll be installing it in a week or so along with a new fuel filter and will update the board.



Thanks

theiceman

You should not be touching the gas to start a CIS car. check your Base CO and make sure your cold start valve ant thermotime switch is working.

2specs

Yeah Ice I know you shouldn't touch the gas but right now it works for me until I can get things figured out.