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Hi All,
I have an annoying problem with the idle on my 1.6 K series engine - the engine starts without problem hot or cold and will idle perfectly for about 30sec- minute then something happens and the engine splutters and almost stall but then recovers after a short period and then runs smoothly until you stop and restart again?
I used to have a similar problem in my old ford, tracked it down to a vacuum leak on the hose that breathed warm air into the air intake system. Used to exhibit similar symptoms basically would almost cut out on idle from cold but after running a few mins would be fine a replacement hose fixed the problem.
Not having the engine yet I dont know if the K series has a similar air intake arrangement.
It maybe worth cleaning the idle contol valve, they sometimes get sticky after being left for a while. Just rub it gentle over with some wet and dry.
I have had an issue with the fuel pump inertia switch, at the moment its bridged with some wire, seems like all is ok, so a visist to the scrappy is in order.
The symptons make me think duff lambda sensor - when you start the engine hot or cold it'll run in open loop mode for a short while (until a certain temp is reached if starting from cold, or for a given time if the engine is already up to temperature), then switch to closed loop.
If the lambda signal is duff, then when the engine switches to closed loop mode, the ecu will try and correct the fuelling on the basis of the duff lambda signal and struggle. If the ecu is unable to correct the fuelling then I suspect the ecu will revert back to open loop as a fail safe.
As a quick test, put a voltmeter on the lambda signal wire, and see what it does - it should read around 0.8v when you first start the engine, and then once up to temperature, it should switch between 0.3 v (lean) and 0.8 v (rich) at roughly 1Hz (at idle, and faster with increased revs).
Tried disconnecting the lambda and the symptoms have disappeared so i imagine the lambda is at fault. Tried the voltmeter as suggested and the reading fluctuated between .74 and .75 with engine warm.
Is there power reaching the lambda heater? Sat on the driveway the heat of the exhaust won't be sufficient to the keep the element up to temperature, though when the engine is under load it should be ample (assuming the sensor is near the manifold).
If your lambda sensor is feeding a signal of 0.74v to the ecu, the ecu will be trying to trim the fuelling, and running pretty lean, hence the engine struggling.
The more i read up on lambda sensors the more i'm convinced that the heater element is not working correctly - looks like the multimeter will be coming out again.