Porsche 911 Hard Start

[Bobber]

My 1983 Porsche 911 SC has become difficult to start when after it sits overnight and even a few hours between starts. When is does start it idles very rough and as I back it out of the garage it does not respond well (hesitates) and and will back fire several times - it will begin to run smoother after approximately a mile, but as stated initially it roughs very rough - especially when idling. After a while it will run smoother and respond much better. Any suggestions?

[DWeg1998]

How long since tune up? Distributor, rotor, plugs, wires?

Putting on a new fuel filter is a very cheap and easy way to take a stab in the dark at the problem. Often an overlooked maintenance item.

[ossiblue]

Originally Posted by Bobber

My 1983 Porsche 911 SC has become difficult to start when after it sits overnight and even a few hours between starts. When is does start it idles very rough and as I back it out of the garage it does not respond well (hesitates) and and will back fire several times - it will begin to run smoother after approximately a mile, but as stated initially it roughs very rough - especially when idling. After a while it will run smoother and respond much better. Any suggestions?

First of all, welcome to the forum ! Tradition dictates that new members post pictures of their rides or risk savage verbal abuse along with heavy doses of deliberately bad advice .

Seriously though, you have classic symptoms of a lean condition CIS cold start situation which may be caused/complicated by several factors--out of adjustment wur, air leaks, bad fuel accumulator or fuel pump check valve, for example. My first advice to you is to eliminate possible problem areas by a systematic testing of components. Do not guess that a component is bad and buy a replacement--you'll spend yourself into debt and frustration.

In brief, cold start requires a richer fuel mixture than warm running. If the fuel mixture is too lean for cold start, you will get the symptoms you describe. As the engine warms, the mixture needs to be leaner and that also explains why your symptoms ease when the engine is warm. The overly lean condition can be caused by a faulty control pressure regulator (wur), bad fuel pump, air leaks, or combinations of all. In addition, faulty fuel pump check valve or fuel accumulator can also be a part of the mix.

If you're getting the idea that your problem can be the result of many different things, you're correct. That's why you need a bit of understanding of the workings of the CIS and a plan to find the problem through the process of elimination.

Use the "Search" tab at the top of the page and type in "cold start problem" or something similar and do a bit of reading. You may discover you recognize many of the same issues that you are facing. Then, ask as many questions as you need with regard to how to track down your problem.

Oh yeah, the above is based on the assumption your ignition is in proper order and I haven't even thrown in the 02 sensor.

Welcome aboard.