I have a 1981 XJ6 with fuel injection. It starts fine but idles rough and at about 400 to 500 rpm for 4 minutes then it goes to normal idle about 800 rpm and runs good. I can't believe it is the cold start injector it is always 90 degrees here. Any suggestions. Thanks,,,,,,Jerry

 

The 'could be' list might get long. Here are some starters

Might be.....

XJ 6 Series III 4.2 - Cold Start EFI Overfuelling

Might be that your AAV isn't working. This is what increases idle speed on a cold engine

Descripton and Function of Aux Air Valve, Series III XJ6


Might be that your coolant temp sensor is skewed. it plays a major role in fueling until coolant hits about 160ºF

Testing the Coolant Temp Sensor

Cheers
DD

 

Of the 3 thing you listed I have already replaced 2. The AFM and the coolant sensor. So the only one left is the AAV. thanks,,,,Jerry

 

The first item on the list is a wiring modification , not AFM replacement


Cheers
DD

 

At one point the car ran fine so I am thinking it is not a mod to the wiring plug.(I hope).....Jerry

 

Perhaps, just a burp of the throttle on start up to clear any extra fuel in the cylinders or manifold. A dripping injector or two might cause that.


My lump does that once in a while, a slight roll, indicative of running just a bit rich.


Carl

 

I checked the AAV as described and it is closed when cold and closed when it get up to temperature, I also checked the plug and it does have 12 volts when running. I guess it is bad. (enclosed are pictures with engine cold). I guess I should remove it and try to clean it. Is the 2 allen screws the only thing holding it to the water rail? Thanks for the help.....Jerry

 

Yes


Cheer
DD

 

I tried bumping the throttle but it speeds up and then goes back down and does the same thing until 3 or 4 minutes have passed. Thanks Doug....jerry