Low ignition timing at idle 25DET NEO

[spudtatoe]

Hi all..

TL;DR - timing at idle is 3 degrees according to NDSI (Android).. unsure if safe 

I recently have been been trying to fix a rumbly idle so replaced a few things etc. I took off my CAS and compared it to a spare one I had from my DE NEO. The one from the de was a lot easier to spin with no resistance whereas the one that was in the DET was quite resistive and wouldn’t spin freely. So I ended up putting the DE cas in and centred it (which was roughly where it was) anyway I happened to look on NDSI and at idle my timing is at 3 degrees?! I was under the impression it should be at 15? 

While driving and cruising at about 100kmh the timings around 30ish but will go higher/lower depending on how my foot is.

Is this a serious issue? Obviously I’m going to get the timing etc checked but I won’t be able to do that until I get back from a 1400km road trip in the car... 

Cheers

[GTSBoy]

The ECU is pulling timing to try to get the idle speed down to target.  This usually happens when you either have a vacuum leak after the throttle, or the idle valve is dirty and stuck too far open.  Both are really common, but the dirty idle valve is more common.  It requires removal, dismantling and thorough cleaning to make it work.  You should be able to see the number of "steps" that the IACV is on via Consult and if it is really low, that's your giveaway to the above.

[spudtatoe]

9 minutes ago, GTSBoy said:

The ECU is pulling timing to try to get the idle speed down to target.  This usually happens when you either have a vacuum leak after the throttle, or the idle valve is dirty and stuck too far open.  Both are really common, but the dirty idle valve is more common.  It requires removal, dismantling and thorough cleaning to make it work.  You should be able to see the number of "steps" that the IACV is on via Consult and if it is really low, that's your giveaway to the above.

So I actually already removed the IACV/AAC and thoroughly cleaned it but when I put it back on the car wouldn’t stay idling after turning on (would instantly die unless revved) and would die after revving it but if I held rpm at around 1k it would idle. So I upped the idle to about 900rpm on the iac screw, I did have the tps plugged in though which I read after it should’ve been unplugged. 

Should i I watch the “steps” when at idle? What’s a number it’s say, fine at? 

I guess what concerns me more is that if the timing being that low when at idle etc is it doing harm with me driving? 

Thanks

[GTSBoy]

Well, seeing as you're still worried about the "while you're driving bit", you should NOT take the ECU's word for what the ignition timing is.  The ECU only knows what the CAS tells it about engine position.  You have taken the CAS off and put another back on, so the real engine position could be different to what it (the CAS) thinks it is.  The only way to know for sure is to put a timing light on the engine and see.  If the marks don't agree with the ECU, then it is time for investigation.  This can simply mean you have to adjust the CAS to make them agree, but it can also indicate a mechanical problem (the pulley can slip on the balancer's rubber).

You should not just wind up the idle on the screw on a Neo (or on many engines) because the ECU is actively trying to control the idle down to the setpoint in the ECU, which is about 650 rpm.  You have opened up a bigger air flow path that the ECU can't control, so it winds the IACV down to nothing, then it starts pulling timing.  I think the IACV steps can be almost any number, if it's actually working, depending on how far open it needs to be to support the load at idle.  But if you see it at low values, like 30 and it's not moving up and down to maintain the idle, then it is probably bottomed out.

You probably haven't done a good job on cleaning the IACV and/or putting it back together. Probably worth another shot.

And lastly, all of this is only for idle.  Unless you have a real mechanical problem causing the low idle timing, then the idle timing maps and control do not play any part when the engine is running on the main maps.  You should monitor the timing while driving.  Run the car at moderate load (up a mild hill) and hold it at a known engine speed (say 3000 rpm).  Note the timing value.  If you can check the TP value on your Consult, then you can look up the standard Neo timing maps for that load and speed and see if it matches what the ECU was commanding.

[KiwiRS4T]

If you have guessed the position of the CAS guess again and advance it a little and see what happens.

[Slap]

Sounds like the reading is actually the Timming added by the ecu. Wich would suggest to much manual advance on the cas.
I believe the ecu normaly adds 10 -15 at idle so it stays at about 30 on idle.... according to my rb25 experiences.

A slight rough idle can happen from an exhaust leak prior exhaust o2 sensor.
The standard ecu on an rb always hunts for the best spot. The more air tight and fresh your plant the less noticeable the hunting.

I would try retarding the car 5-12

[spudtatoe]

11 hours ago, GTSBoy said:

Well, seeing as you're still worried about the "while you're driving bit", you should NOT take the ECU's word for what the ignition timing is.  The ECU only knows what the CAS tells it about engine position.  You have taken the CAS off and put another back on, so the real engine position could be different to what it (the CAS) thinks it is.  The only way to know for sure is to put a timing light on the engine and see.  If the marks don't agree with the ECU, then it is time for investigation.  This can simply mean you have to adjust the CAS to make them agree, but it can also indicate a mechanical problem (the pulley can slip on the balancer's rubber).

You should not just wind up the idle on the screw on a Neo (or on many engines) because the ECU is actively trying to control the idle down to the setpoint in the ECU, which is about 650 rpm.  You have opened up a bigger air flow path that the ECU can't control, so it winds the IACV down to nothing, then it starts pulling timing.  I think the IACV steps can be almost any number, if it's actually working, depending on how far open it needs to be to support the load at idle.  But if you see it at low values, like 30 and it's not moving up and down to maintain the idle, then it is probably bottomed out.

You probably haven't done a good job on cleaning the IACV and/or putting it back together. Probably worth another shot.

And lastly, all of this is only for idle.  Unless you have a real mechanical problem causing the low idle timing, then the idle timing maps and control do not play any part when the engine is running on the main maps.  You should monitor the timing while driving.  Run the car at moderate load (up a mild hill) and hold it at a known engine speed (say 3000 rpm).  Note the timing value.  If you can check the TP value on your Consult, then you can look up the standard Neo timing maps for that load and speed and see if it matches what the ECU was commanding.

Right cheers, I’ll get the timing checked and confirm that base timing is correct then I guess adjust cas from there. 

I’d say you’re correct about the iac being bottomed out, at idle it sits at about 30-31 and doesn’t move. 

I’ll adjust it back to what it was.. should I be removing the tps connector when I wind it back? 

The highest the timing went was about 50, on a whole hour drive,

i went up a moderate hill going 100kmh at 2500rpm and the timing was about 30-40 depending on the accelerator, I found the high 50 timing was say when I was in 3rd gear moving along at a constant rpm probably on a slight hill.

7 hours ago, KiwiRS4T said:

If you have guessed the position of the CAS guess again and advance it a little and see what happens.

Hmm it was marked on the old cas so I tried to get it as close to that as possible.. I’ll see if I can compare it again and check.

5 hours ago, Slap said:

Sounds like the reading is actually the Timming added by the ecu. Wich would suggest to much manual advance on the cas.
I believe the ecu normaly adds 10 -15 at idle so it stays at about 30 on idle.... according to my rb25 experiences.

A slight rough idle can happen from an exhaust leak prior exhaust o2 sensor.
The standard ecu on an rb always hunts for the best spot. The more air tight and fresh your plant the less noticeable the hunting.

I would try retarding the car 5-12

It’s not really a slight rough idle.. it’s pretty aggressive. The rpm doesn’t hunt, stays the same but the car will be shaking all over the place, some days worse than others and only noticeable when the engines warm form what I can tell

[GTSBoy]

8 hours ago, Slap said:

Sounds like the reading is actually the Timming added by the ecu. Wich would suggest to much manual advance on the cas.
I believe the ecu normaly adds 10 -15 at idle so it stays at about 30 on idle.... according to my rb25 experiences.

I would try retarding the car 5-12

Sorry, no.  All wrong.

Idle timing is a real 15° (manual), or 20°(auto).  30° at idle would be a shitshow.

[Dose Pipe Sutututu]

9 hours ago, Slap said:

I believe the ecu normaly adds 10 -15 at idle so it stays at about 30 on idle.... according to my rb25 experiences.

Wtf? No man.

Your experiences must have been with incorrectly timed motor ie incorrectly installed cam timing belt.

[Slap]

It's 30 with ignition added form the ecu I'm certain. So as a total.
I'll scratch around but I'm sure.
Everything I can remember about the stock ecu and it's hunting for perfection is a bit vague.
Base case trimming 15-17
Ecu adds about 10 -13
Depending on fuel used as the ignition will add as much advance as it can at idle going back and forth adding and subtracting timming and fuel in accordance to air fuel ratios and knock voltage.

Maybe I'm wrong ... time to dig.

[GTSBoy]

No, the absolute static idle timing is 15°.  The ECU's knowledge of the engine's position is based on the assumption that the CAS is adjusted so that its TDC point is the same as the crank's.  That, of course, puts the ECU at the mercy of the idiot twiddling that CAS position.  But when everything is set correctly, the ECU says that the idle timing is 15° because that's what it is.

[Slap]

No I believe you are wrong in a way.

Im sure that is the timming added by the ecu.
Pull the light out and compare what the ecu says to the light.

The ecu assumes that it is at 15. But doesn't hesitate to change it if it can change it whilst staying within parrameter of the knock and the air fuel ratios. If it's still on one side of the parrameter it will continue that way until it has passed it and then head back trying to narrow in on it's best idle that it can provide.

People use cam gears all the time with stock ecu. That will change cas. The impacts of the car changing can be within reason ironed out by the ecu while it isn't using load maps. But the load maps won't be altered and that's where people adjust the cas to correct load maps and let the ecu fix low load and idle.

It is not hard to check if that is all that is wrong.

Retard the cas a bit and check. If you over advance and drive it is way worse if than retard.

You prove it to me and I will believe you gtsboy show me a document or something.

Even if I'm wrong how hard is it to check!

[Dose Pipe Sutututu]

You are so wrong,

ECU strategies may add a bit of timing when the motor is cold and or for idle control but the base idle timing without any form of ignition compensation is 15 degrees on a stock ECU.

Also good luck trying to control idle with 30 degrees of timing.

[Dose Pipe Sutututu]

Whoever is reading this thread, please ignore what @Slap is saying.

Nothing worse than cracking some ring lands or destroying your motor due to knock.

Do not advance your motor by 15 degrees on top of the base timing. You'll end up poorer and in tears.

[Slap]

Whoever is reading this thread, please ignore what [mention=150098]Slap[/mention] is saying.
Nothing worse than cracking some ring lands or destroying your motor due to knock.
Do not advance your motor by 15 degrees on top of the base timing. You'll end up poorer and in tears.

I never said that . Get some glasses.

[Slap]

At idle the car will advance itself from 15 base at the crank.

That is what I'm saying

 

I never said set it to 30.

[Slap]

Don't manipulate what I say.

 

[emoji35]

 

 

 

[Slap]

This is a forrum. And discussion is great. But when you want to prove someone wrong do it correctly and pull up some fact sheets

[Slap]

Also an aggressive idle can be from Over advance.
Lumpy if under advance.

[Slap]