Idle issues when hot

[Bollah]

Not to long ago, I wired in my idle control valve, with some invaluable help from you guys here and now I get a nice idle from cold start and when up to temperature with day to day driving, but I have an issue that if the car has been in a traffic jam or some sort, once the air temp is reaching high 30's / low 40's, it doesn't really want to idle and cuts close to cutting out, with the revs bouncing around.

What would be the recommended solution for sorting this? Use the Air Temp Compensation as by looking on the ECU, it looks set as a default and the ignition values are all set at 0% and the fuel correction is various values.

Thanks

[stevieturbo]

What values do you have in the idle table ? What compensations or corrections are being applied when idle is unstable ?

[Bollah]

Stevie

I don't think any corrections or compensations are being applied when it gets hot, hence why I would like to sort this out if possible

The idle settings are as below :

[stevieturbo]

Cant really see any sense in idle control going as high as 1900rpm or as low as 200rpm. The sites could be changed to offer you more resolution
After all, you've set idle control to turn off at 1500rpm anyway. So if at any point it hits 1500rpm, it turns off and the rpm will fall, and this can cause oscillation.

Too fast a control loop delay can also cause oscillation, try 1-2secs at first.

For starters, I'd fill the entire duty map with the same number, then adjust as necessary to achieve a decent idle. Turn PID's OFF at this stage.

You can then raise numbers at lower rpm up slightly so it will open the idle valve slightly. TBH numbers at higher rpm's I'd just leave them the same unless you have a specific problem they seem to be causing.
On my own, car, having any large number changes would also cause oscillation. ( by large, even 10 was enough )
it is trial and error, but start with all numbers the same.

Open the 20x14 map, look at what's happening with the base PWM and then any adjusted PWM if you have PID's turned on. But try it all open loop first so you get a good base PWM map so the closed loop has less work to do.

When googling the Ford idle valve, 300hz seemed to be the preferred frequency. No idea how much of a difference other valves will be, or if it really makes much difference.

[Roverdose]

are you hitting over 100dgr if its been sitting in traffic?

you map only goes to 103 and its at 35%, if your touching 104+ the valve will be closed!

agree with steve on the revs.

Drew

[stevieturbo]

are you hitting over 100dgr if its been sitting in traffic?

you map only goes to 103 and its at 35%, if your touching 104+ the valve will be closed!

agree with steve on the revs.

Drew

you sure about that ? normally when you go "off map" the value stays the same

ie it will stay at 35% regardless of whether it's 104, or 400degC

There is no "turn off" feature based on engine temp. My own PWM map only goes from 0-80degC as by that stage the engine is warm anyway.

Only reason you might want to use sites at 100+ is to raise engine speed above 100degC to assist water flow to help cool it or something.

[VR6Turbo]

I know this issue only too well. You park up for 20 mins, start the engine, and then heat soak causes the idle to be too slow for the same given PWM that was fine before stopping the motor.
OEMs have a strategy for this by holding the revs at a set rpm for a few seconds before slowly lowering back to target. DTA can't do this as there is no intake air temp comp for idle, and as with the fuel closed loop, the idle one is also way too slow.

As Stevie says, slowing down the PID response often helps, but if the PWM is too low, it can take a while to bring the idle back up to target. And yep, big PWM steps like 100>70>50>35 + a fast refresh rate will cause huge oscillations. Keep it at 50 and then slow down the PID.....but you might need to richen the fuel table around the idle cells....or use the % increase in the idle comp map.

It's just another typical DTA scenario you have to 'work around' unfortunately.

[stevieturbo]

And dont forget.

Often it is best to set your base hot idle using the throttle blade with idle PWM set to zero.

Then it should never really be able to fall much below this rpm, and idle control is mainly used to stabilise it and offer a high cold idle etc.

Obviously every engine will be different though. I'd say the smaller the engine or more unstable the idle, the more you want to leave the throttle opened

[Bollah]

Thanks for all your input on these guys.

Stevie, no idea on why I didn't specify the cell range to be from 700 - 1500 offering more control, such an obvious thing to do now that you mentioned it.

I have changed the values and it's certainly much better once heat soak has happened. Just need to tweak it here and there and hopefully it should be a lot better