Cold start issue on Fuel Injected car

dcioccarelli

dcioccarelli

Dominic Cioccarelli
Hi all,

I have a slight issue with my fuel injected X1/9. If I adjust it to run well when it is warm, it will idle too low when it is cold. I understand that the ECU (my previous experience has only been on carburettor models) has the following sensors:

- thermo time switch
- cold start valve
- coolant temperature sensor

I'd like to locate and test the operation of all of the above. I would imagine that the coolant temperature sensor is not the same one used to drive the temperature gage on the dash.

Any advice and / or photos would be appreciated.

Thanks,
Dominic.
 
Dom... you really MUST...

... download the FI Troubleshooting Guide... PRINT it, READ it cover to cover, then SYSTEMATICALLY walk though the process until you resolve the problem.

Any other way would be guessing...

http://www.angelfire.com/wa2/fits/index.html#ljetguide

Also, go to the INDEX, then to Version 1.0, then select BEST OF in upper right hand corner... and gleam all the other info.

Let us know what ya find.
 
We can pretty much exclude the cold start valve and the thermo time swithch; These are used for cold start fuel enrichment, but are only active for seconds after you start cranking the starter. On the order of half a dozen seconds if it is really cold, less time if warmer.

What I have seen from KE-Jetronic cars is that if the throttle posision swithces are not working, idle becomes unpredictable (may work fine on warm engine, goes haywire if the A/C is turned on etc.). This should be easy enough to test.
 
My guess

Cold idle speed is controlled by the auxiliary air valve (I think Fiat calls it the cold air valve or something).

It allows extra air past the throttle plate when the car is cold, slowly closing as the car warms up. The valve itself is actually electrically heated, as well as heated by the engine block.

The valve is located down low on the plug side of the motor, towards the rear (transaxle end). It has two hoses going to it-- one from the large rubber intake between the AFM and the throttle body; the other hose goes to the plenum.

Inside the valve is a bimetal spring that opens and closes a disc type valve (think slide throttle for a mental picture) based on the valve's temperature.

If your car idles relatively smoothly (i.e. not missing, etc) and just idles too slowly then this valve is the likely culprit. It could be plugged, the bimetal spring could be broken, etc.

But if you're lucky it's still working and can be adjusted to open more. I'm not sure about the one on our cars, but most (if not all) aux air valves can in fact be adjusted. There is a very small nut (4 or 5 mm probably) marked with yellow paint which can be loosened, allowing the stud to slide in an arc (if my memory serves-- not positive about the motion of the adjustment but if there is one it's a small nut). Looking inside the valve whilst tweaking the adjustment will show you which way you need to go to add more air when the valve is cold.

Oh, and here's a little tip-- if you're running a hot cam or live somewhere where it gets really cold and you want the car to warm up faster at idle, disconnect the electrical connector to the aux air valve. As long as you don't have the valve adjusted way far open the engine block heat should eventually close the valve, returning idle to normal. But it'll take a lot longer, meaning more idle speed to help warm the car and overcome cam overlap. :)

HTH,

///Mike
 
ok, will check...

Hi Mike,

I checked the other things from the FI troubleshooting guide that Tony mentioned and this would seem to be the most likely culprit now that I have a better understanding of how the system works.

The electrical connector going to my aux valve was corroded on one terminal, but as I understand it this would only delay the point at which the valve closed (should close anyway from the block temp).

I'll take the valve apart today. Looks a little bit trick to get at, but I only had a cursory glance yesterday.

Thanks again.
Dom.
 
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