Correct behaviour of idle on 2.0 EFi Pinto

[peter_m7uk]

Hi, I'm not sure if I have a problem with my Pinto 2.0 EFi idle or not, can someone tell me what is the correct behaviour??  It used to idle faster when cold, then drop to 875rpm when warmed up - I thought this was right, as I've seen other engines do similar, but then I read elsewhere online someone saying that was a problem to fix!!    I recently serviced the engine and found that it no longer idles faster when cold, it's just 875rpm all the time - So is this right or wrong?

[alanrichey]

Sound like the temperature sensor for the ECU has failed.  Not sure how your ECU works, but in mine if the sensor fails the ECU uses a single default value equivalent to a warm engine.

[Derek]

This might help to diagnose the problem

 

 

[peter_m7uk]

Thanks for the comments, Alan and Derek.   However, that temperature sensor is brand new (part of the servicing I mentioned) and it returns the correct voltages according to Derek's article!  

This makes me suspect that a lack of high idle speed when cold could be correct!  Which brings us back to my original question - "What is the correct behaviour??"   I can't diagnose anything if I don't know what I'm supposed to be expecting, that is the number 1 key point here..

[Jez Morton]

I've had an efi in my kit for 15 years and I couldn't tell what it's supposed to be. I know it fuels more when cold so a higher idle is most likely normal. I think efi is more of an electric carb tbh. If its your temp sensor at fault you get high rpm when warm, mine did.

[peter_m7uk]

42 minutes ago, Jez Morton said:

I've had an efi in my kit for 15 years and I couldn't tell what it's supposed to be. I know it fuels more when cold so a higher idle is most likely normal. I think efi is more of an electric carb tbh. If its your temp sensor at fault you get high rpm when warm, mine did.

Hi Jez, thanks for the reply.  Out of interest, are you going to run the engine any time soon??  If so, could you look at the rev counter and tell me the speed when you first run cold, please?  If you're going to warm it up as well, then could you give me the rpm when fully warm too?  I don't have anything to compare my engine to, so that would be very helpful.  Thanks 

[IanS]

A long time since I did anything with this setup.

But I recall that the idle speed is controlled by the idle control valve which is prone to sticking. This sticking causes the engine to stall. So adjusting the throttle stop to increase the idle is a common "FIX". Then you need a bit of throttle to start the engine and if it is not to cold this works.

As I recall short time of increased idle was normal on a fully working engine.

Idle valve sticking normally cured by carb cleaner, the valve is closed at any power setting above tickover. Its main use was to improve MPG whilst in start stop driving conditions by having the lowest possible tickover so adjusting the throttle stop just costs you a bit of petrol.

[Jez Morton]

14 hours ago, peter_m7uk said:

Hi Jez, thanks for the reply.  Out of interest, are you going to run the engine any time soon??  If so, could you look at the rev counter and tell me the speed when you first run cold, please?  If you're going to warm it up as well, then could you give me the rpm when fully warm too?  I don't have anything to compare my engine to, so that would be very helpful.  Thanks 

When cold somewhere between 1000/1200, then drops to 900 warm.

[peter_m7uk]

On 11/17/2023 at 9:04 PM, IanS said:

A long time since I did anything with this setup.

But I recall that the idle speed is controlled by the idle control valve which is prone to sticking. This sticking causes the engine to stall. So adjusting the throttle stop to increase the idle is a common "FIX". Then you need a bit of throttle to start the engine and if it is not to cold this works.

As I recall short time of increased idle was normal on a fully working engine.

Idle valve sticking normally cured by carb cleaner, the valve is closed at any power setting above tickover. Its main use was to improve MPG whilst in start stop driving conditions by having the lowest possible tickover so adjusting the throttle stop just costs you a bit of petrol.

Thanks Ian, but the idle control valve is brand new.   When I changed it, the behaviour was the same as before, so I suspect the old one is actually fine!

[peter_m7uk]

On 11/18/2023 at 10:19 AM, Jez Morton said:

When cold somewhere between 1000/1200, then drops to 900 warm.

That's great Jez, really useful, thanks!    After all the things I did with new temperature sensor, new idle valve, new plugs/leads/coil and tightening up the intake manifold bolts, I then looked at adjusting the idle screw on the intake with the figures you just gave me.

I found that it was insensitive if too far one way (permanent low idle speed) or the other (permanent high idle speed), but once I got it in the middle it was pretty sensitive to changes of 20 degrees turn (about 1/16th of a screw turn).  In one position, it idled at 1500rpm cold and 1000rpm hot.  If I turned it just 20 degrees anticlockwise, it changed to just over over 1000rpm cold and just under 1000rpm hot, which sounds identical to yours.

I think I've therefore solved the problem and got the correct idle behaviour back, thanks again!