Hunting issue

[jondee86]

According to what I have read, when the engine is up to temperature
ignition timing at idle is retarded from engine driving timing for idle stability.
On cold start there is extra timing added which tapers off as the engine
comes up to temperature and the idle speed drops to normal. The ECU will
add timing advance as a "stall saver" if the idle rpm starts to drop. It is also
likely that the ECU will adjust the mixture richer at idle.

So it does seem that the OEM ECU and the Freedom use similar strategies.

Cheers... jondee86

[totta Crolla]

Freedom has a basic water temperature fuel correction for cold start and running I'm not sure about timing, something I can check.
Certainly I can replicate a hunting idle by using different 'on idle' and 'off idle' points, a setting that allows TPS IDL switch tuning.
Freedom Idle ignition timing can be set and will not change as long as the IDL switch is engaged, as soon as it goes off idle the ecu uses the normal ignition map. There is no specific idle fueling, it just uses the normal fuel map.
If the stock ecu has the same strategy and the IDL switch is not engaged it is possible for the idle timing to jump around the ignition map and a change here will effect the engine speed and fueling.

[jondee86]

In the case of a factory ECU and stock engine, the idle quality is actually
very good if the engine is well maintained and tuned to specification. It is
one of the strong points when comparing stock to aftermarket ECU's.

When problems arise it is usually because adjustments have been made to
things that should not be adjusted, and the engine is no longet tuned to spec.
If the throttle stop screw has been messed with, not only does it throw the
TPS setting off, but the blade may not be closing fully, allowing extra air
into the manifold. Looped vacuum hoses can cause permanent high idle.
Messing with the ignition timing because someone said more advance will
make extra power, will raise the idle speed. And anything that changes the
MAP reading at idle will mess with the fueling.

So many ways to get it wrong and only one way to get it right

Cheers... jondee86

[totta Crolla]

"not only does it throw the TPS setting off, but the blade may not be closing fully"

and that Jondee could well be the problem in this case, even if the TPS is set to factory specifications it could still be out ?

[kazi]

So last night I adjusted the TPS while the engine was running outside diagnostics mode which stopped the hunting but meant it did odle high. 2500-3000 rpm. I also set ignition timing out with diagnosis mode to 16deg BTDC. This brought it down to 1500 and not hunting. Someone sujested that a faulty thermostat could cause hunting issues also.

I removed old themooand tested in hot/cold water and it didn't do anything. Have swapped that for one out of my Paseo (same figment just opens at 72.5deg) I've ran out of coolent so will get some today to see if this could be the issue. If not I'll work on what I've got

---

In regards to the blade not closing on the first TB we played around with the stop screw etc etc and managed to get it to idle at 1k but still hunting. With the 2nd TB, this was still as OEM setting and still hunted.

[jondee86]

(05-03-2017 03:29 PM)kazi Wrote:  In regards to the blade not closing on the first TB we played around with
the stop screw etc etc and managed to get it to idle at 1k but still hunting.
With the 2nd TB, this was still as OEM setting and still hunted.

If the engine was idling at 1000rpm and hunting, then it was not cycling
on the fuel cut. Fuel cut requires the rpm to go above 1700-1800 before
fuel gets cut off. When it cuts off the rpm drops to 1200-1300 before the
fuel turns back on. That's how fuel cut works.

If you were getting hunting at 1000rpm then it is a different kind of hunt...
probably rich-lean hunting. That gives a nice gently up-gently down kind
of hunt... not a big drop down and climb back up kind of hunt.

If your thermo was stuck closed, then it is likely that your temperature
gauge would go high while driving. Might not be obvious if the engine is
only idling in the shed. Standard thermo is 82deg IIRC. A 72deg thermo will
open too soon and probably leave the engine running a little bit rich all
the time. See what happens when you run the engine.

You can't set the timing correctly with the engine at 1500rpm. You need
to get the rpm down to 1000 or less to set it with any accuracy. Right now
the timing is most likely retarded by 3 or 4 deg from where it should be. You
have to find a way to get the idle down... put some kind of rubber plug in
the AAV port if you have to and adjust idle with the bypass screw. Get it
to around 950rpm and then set the timing @16 without jumping the plug.

Cheers... jondee86

[kazi]

SORTED!!!

Took the car for its MOT and got them to have a look at it. TPS was tripped and cleaned and throttle body was taken apart and rebuild. The smoke test that garage did found that there was an air leak from the TB spindle on the cable side hence the TB strip and rebuild. Put back together and it still hunted. All the water piping then got taken off. The offender was found to be a small bit of silicon stuck in the port at rear of engine where the 2 green/red plugs are.

My guess as to why would be that there was no gasket on the thermostat housing and when I removed the old thermostat there where small deposits of silicon on the rim.

Everything was put back together and TPS are set and she now runs with a full years ticket!

[totta Crolla]

This was a thankless task.....
Someone else to go on the 'don't bother next time' list.

[kazi]

Sorry. I was up north of Scotland and there is little to no signal and just wanted to write something I was that exited. Just going to get the car now. So please don't jump to conclusions. I'm always grateful for all the help I receive and have done.