Cold start stumbling, corrects in about 20 seconds

I highly doubt that it is the auxiliary valve. Our cars do not really need it. Actually mine is closed off and I know Bellbloke's one too.

What color is the smoke? Does it smell like petrol?
If you think you get to much fuel. There is a cold injector on the airhouse (blue connector) on top of the intake manifolds. I would start with disconnecting this one just to see if it gives a better start. This way extra fuel is not injected during a cold start. If it start better then you at least know it is getting too much fuel. It is merely a test and not the resolution.

There are some troubleshoot steps here. It will be the same with your CH model. All K Jetronic have the same principles.

https://www.scribd.com/document/49652595/Problems-With-K-Jetronic-System
http://www.type17.ch/downloads/Injection/Bosch%20-%20K-Jet%20-%20Workshop%20Manual.pdf

Personally I think you would have a vacuum problem.

 

It should have it #46

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An easy way to test the AAV is to remove the rear hose. Then you can put a small screwdriver inside the AAV to see if the plate is working. If it's cold, there should be an opening you can put the screwdriver through, and move the plate against the spring tension. When the motor is warm, the plate should fully close off the opening.

A vacuum leak probably would not go away when warmed up. Sounds more like your spark plugs are fouled. You can clean them with a torch, or just replace them. Also could be your injectors getting clogged. There are small filter screens inside the fuel injectors that will clog when the fuel dries out of them. It helps if you start the car every day, so the fuel never dries out. Also run a fuel injector cleaner like Techron.

 

There is actually a workshop manual on the KE3 of the Mondial.

http://workshopmanual.com/doc/d828-bosch-ke3-jetronic-539-89-injection-system-manual-328-mondial

 

Where is the air admit valve (AAV)you are speaking of. I am having a similar problem.........hard to start cold and lots of gas smell......I am thinking the cold injector is the problem. Rough idle and little power at lower rpms. Sound is slightly off.

 

AAV is the device under the coolant expansion tank. Proper operation is to allow more air into the engine (which also allows more fuel) at start up, so you have a higher idle speed. Idle speed should gradually reduce automatically as the motor warms up. This is the plate inside the AAV closing. Failure modes are usually stuck open, or stuck closed. A shot of WD-40 will usually free up the plate.

Your problem sounds like you have the metering slits in the FD plunger clogged. This is from sitting and letting the fuel dry out and/or old fuel. Fuel should not be more than 6 months old. You can take the plunger out and clean it, or start running a fuel system cleaner like Techron.

 

Yup, you can, but like spicedriver said it's open during cold start. You can disconnect the two hoses from the AAV and tape them together. This way you do not have to unbolt the AAV.

 

Yes, the AAV is just in physical contact with the outside of the coolant expansion tank (no wetted surfaces).

Approx. for how many seconds do you have to crank the starter motor before it fires up when cold? Like the suggestion to try unplugging the cold start injector as a simple diagnostic first step to see if it changes anything (in fact, to simulate how the cold start injector should work you could crank it for a few seconds, unplug the cold start injector, and then try cranking a bit more). You posted that "the car will start with a bit of cranking", but the thermo-time switch should only allow the cold start injector to squirt fuel for a couple~few seconds (even if you crank the starter for a longer time). A faulty thermo-time switch stuck in the closed condition could cause too much fuel to be squirted -- just an initial thought...

 

Should be open when cold. Closed completely when warm.

What is the ambient temperature ? When is the last time the motor ran ?

Post 5. Put a small screwdriver through the opening and try and move the plate (up in the pic) against the spring tension. If the plate moves freely, the unit is probably okay. If stuck, spray some WD-40 on the plate. If you want to see if it opens completely, put it in the refrigerator.

 

You can try and jump 12V across the heating element. If it doesn't close all the way, it's faulty. Try some WD-40 anyway.

Motor should run without the AAV. If the hoses are taped together, should be a high idle. If the hoses are taped off, should be a normal idle. If the hoses are left open, there will be a really bad vacuum leak, and motor will run rough.

You could probably find a used AAV on ebay. These were used in a lot of different cars.

Still, I think your problem is ignition related. Ignition or fuel. Run the car from cold for the 20 seconds or so, then turn it off. Touch the exhaust pipes close to the head, or the little test pipes if you have those. They all should be warm. If any are cold, those cylinders are not firing. First guess would be faulty plugs, or plug wires. Or fuel clog somewhere.

 

metering slits in FD........what is a FD? Frequency device? same as Frequency valve?

 

FD = Fuel Distributor

The metering slits are in the plunger. Very small and easily clogged. Fortunately, the plunger can be removed and cleaned without splitting the halves.

http://forums.pelicanparts.com/porsche-911-technical-forum/272657-cis-fuel-distributer-cleanout-w-pics.html

 

Check all 8 extenders connecter to your sparkplugs. they are know for having small burn pinholes if one goes through the plastic it spark will jump from time to time into the wrong direction. There will cause the engine to run not on every cylinder.

You can use insulation tape for a quick fix to wrap it around the extender.

 

Just a note on the AAV - I check my 3.2 cold (80 degrees F ambient), and the opening is about the same size as in the pic posted above. After 10 minutes of running checked again and it's fully closed.

 

Glad that she's running again.

I believe the guys who remove their AAV block off the hose, so the idle is always low at start-up. This is one of those times where I think the engineers who came up with this stuff are smarter than me, and mine gets left in place.

Just swapped from Champion to NGK not too long ago. Mine came from the factory @ .024. There was a posting about this somewhere on here that suggesting leaving the tighter gap in place, and not open to .028. This is what I did, and it seems to work well.