Cold Start Surging Idle 3.0 SC
 

I searched. I did! I did!

There are several threads about 3.2 idle.. but what about my 3.0?

I have the heater motor out and can see in there now.

Can I fix this myself?

It surges when cold started. All the rest of the time, it idles just fine.

I'm not sure what you used as search terms, but there are a lot of threads on cold idle surge, likey due to a (cold engine) rich mixture. You need to check the control pressure regulator's (WUR) pressure specs for your engine.

A way to verify this is to slightly lift the air flow sensor plate while this surge is occurring. If the idle speed drops, it's a pretty safe bet the mixture is too rich. Then use a pressure gauge to verify. Lots of info on this subject on this forum.

Try using terms like "WUR" , "hunting idle" and "mixture". Check out Jim's site on CIS. There is also lots of info on how to use the "fuel pressure gauge" to check your WUR.

As Jim said, it's quite often a too rich mixture, usually from rither an out of spec WUR or from something else, like a vac leak, that someone has tries to make up for by setting the mix too rich. This usually results in an oscillating idle speed.

I also have a very long thread on several problems I had simultaneously that led to start and run problems.

Yes you can, as long as you have the CO adjusting allen that every CIS owner should have, then back off the mixture to lean it out...what could be easier?

If all that is off is his mixture. If, however the WUR isn't working properly then adjusting the mix will fix the startup issues, and created issues once warm - i.e. too lean.

Option 1: Get your hands on CP gauges and the proper CP tables (its different for different years) - make sure your WUR is working properly then adjust your mixture if it is. If its not, then there are ways to adjust it - do a thread search for "WUR" "Adjustable" or "Repair"

Option 2: Gut-check adjustments done while warm. Never adjust the CIS mixture screw while cold. During warm-up, the control pressure (and thus the mixture) will be constantly adjusting. Ideally, the engine should above 180F oil temp (well, that's where mine stabilizes on a "cool" day). From there, make an adjustment, then drive the car. A CO meter is best, but from a gut check, here's what I do.

1: Make a small adjustment, remove the wrench, get back in the driver's seat
2: Drive the car - preferably on an empty road. Run the RPMs up to 4k-5k, hold for a second, pop the clutch (specifically take the car out of gear while rolling). If the car is too rich, the RPMs will fall very fast, past the idle setpoint. If its way to rich, it will stall.
3: Stop, make small adjustments toward lean & repeat.
4: Make your last adjustment toward rich - i.e. go just past where the idle holds, then back up toward rich.

Hopefully, your idle mixture is too rich, and fixing that will fix your cold-start issues. If not, its something more complex so make sure you don't go adjusting your mix while the engine is cold.

Good luck.

I don't have gauges,,(yet) so, for now I might try turning the adjustment mixture allen out counter clockwise just a little, as described above.

I have some long t-handle allens, but do I need a special one of some kind?

And, of course, where IS that adjuster that I'll be adjusting?

If it is a special allen required, I'll get my order off to Pelican, pronto..

I had this same issue on my SC. Small DME relay under the passenger seat. $25 replacement and all problems solved.

On a 80-83 SC that might fix the problem, if the ECU relay failed. The 78 & 79 don't have ECUs as they don't have a Lambda system.

As to Scot's question - a long-handled 3mm hex key should do the trick. The hole for the key is on the fuel distributor located in front of the air filter on the passenger side. The hole itself is on the driver's side of the fuel distributor.

Additionally, there is the idle-bypass adjustment on the driver side of the assembly (other side of the rubber boot thingy - real technical) that uses a flat-head screwdriver - but you really need an offset one to get leverage. Adjusting the mixture may adjust your idle - use this to correct it.

I don't have any pictures, sorry.

Take a look at this thread http://forums.pelicanparts.com/porsche-911-technical-forum/232089-cis-idle-speed-mixture-setting-without-analyzer.html
and this one
http://forums.pelicanparts.com/porsche-911-technical-forum/437101-cis-mixture-tool.html

it only takes a 3mm hex key, but trust me :) you can mess it up.

Jay