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Discussion Starter #1
Hi all,

I've got a 2004 1.4L 16v BCU engine and it starts fine when its cold but then after even a short drive when I turn it off and on again it starts to do serious hunting. It sometimes idles as low as 400RPM and stalls. There are no problems when starting to drive and has no issue with generating power when accelerating so it makes me think it cant be a misfire. The engine makes a sharp hissing sound (almost like a turbo exhaust) when pressing the throttle so almost as if its happening for a split second when the throttle opens, not sure if this is related. I have listened and the hissing sound is coming from the back of the engine (around EGR, throttle body, air intake etc).

I have scanned the car and it came up with the following engine codes;

-17852 Potentiometer for EGR implausible signal
-16500 Engine Coolant temperature sensor 1 circuit range/ performance

There were no check engine lights prior to this and I have cleared the codes and driven 100 miles and still no check engine light. The battery light comes on when its about to stall but as far as I am aware that's standard whenever a car is stalling. No other maintenance lights. The only other code from the scan is 01336 ' Combination comfort databus', but this comes up when scanning the electrics and not the engine, not sure what it means either.

I've made two videos of the normal idle when starting cold and the dodgy idle after a drive, which may help diagnose:

Cold start (seems normal);

Idle after a drive and turning off and on (car stalls), note that I start revving on the 3rd start so that the engine isn't flooded (my revs are only when it goes above 1000RPM all else is the car itself);

I have purchased a new EGR valve and will be taking out the throttle body to clean it out as I suspect this might be the issue given the code. I will keep you all updated if I solve it or if there is still an issue after the EGR change but please reply with any advice you may give as this is seriously stressing me out.

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