idle speed

[Boydskyking]

I have a 1980 porsche targa 3.0 and I have two problems ,,, My engine starts good but idles rough, misses about 950 rpms but as it warms up it will slowly continue to increase in rpms with no input from the accelorator.second where can I buy the shims to shim my fuel pressure as in checking my fuel pressure it runs at 68 pds and would like to get it up to 75pds. Two shims would do it

[matt demaria]

It does not sound like a system pressure issue. First check pressures. cold pressure about 70 degrees is about 2 bar. Warm pressure is 3.4 to 3.8. It sounds as if the co is out of calibration. Check pressures of warmup reg first. If ok diconnect o2. If there is a big change, co is out of calibration. They normally drift out especially over a years time; and/or there could be a vacuum leak. It is also possible that an injector could be bad.
Always check pressures first for a cis system and we are also assuming that the basic engine is healthy.

[Scott R]

Is this a ROW or US 80?

[Boydskyking]

This car is a us car. My guage reads in pds so you need to convert br to pds first.The injectors have been cleaned and flowed,ignition is set right,new plugs and plug wires , rotor and cap.and real good valve ajustment. The aux air regulator seems to be working right .i removed it and applyed 12 volts to it and it closed in about 5 minutes.I dont think I have a vacumn leak. I bought a pressure checker from pelican and the primary fuel pressure is 68pds and the control fuel pressure is 32 pds engine cold at 90 degrees outside air temp.The control pressure held for about 20 minutes and then then becane to slowly bled down.one thing I didnt tell you is when I bought the car it had a stainless steel exhaust system which doesnt have place to screwin the o2 probe into the exhaust.Any suggestion. I am looking for a baung that is made out of stainless so to weld it to the the exhaust system. I like the fact that you guys are taking the time to help me appriciate it very much

[Scott R]

2.2 bar control pressure is OK for 90 deg F. At 50 deg F it would be 1.8, but does the pressure change when the electrical connector is on the WUR?

As far as the O2 sensor goes, there are two schools of thought on the late CIS cars. The first is to disconnect it and set the mixture around 3.0 and go with that. The second is to connect it and set the system to 0.8 ~ 1.0 and drive it.

Now, on to the idle issue. The first thing I had happen to me was the advance weight springs in the distributor broke. This would cause the idle to go out, and normally stick on the high side.

The second or first thing to check after that depending is the mixture. If you hookup the o2 sensor you read the output on a common dwell meter and check the mixture viz the duty cycle output on the lambda unit. Other wise a gas analyzer will do the same thing if you have access to one.

I also wouldn't worry to much about that system pressure reading. It's not out of spec at 69 really. And if you want to adjust it the "shimms" an be mined from just about any CIS car in the wrecker yard.

So check the mixture, and the advance and post back up. In the meantime start searching here. Just about every piece of 911 CIS informatation ever gathered is on the forums. Also this is a good reference:

CIS Primer for the Porsche 911