Jump to content
SAU Community

Low ignition timing at idle 25DET NEO


spudtatoe
 Share

Recommended Posts

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

Link to comment
Share on other sites

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.

  • Like 1
Link to comment
Share on other sites

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

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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

Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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.

  • Confused 1
Link to comment
Share on other sites

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.

Link to comment
Share on other sites

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!

Link to comment
Share on other sites

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.
Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share




  • Similar Content

  • Latest Posts

    • The two diagrams are equivalent. The R32 one is just one sheet out of about 3 showing everything in the whole car all at once. And without knowing the functionality that occurs in the modules, they are both equally opaque.
    • 8v - 2.48ms 9v - 2.15ms 10v - 1.74ms 11v - 1.41ms 12v - 1.15ms 13v - 0.99ms 14v - 0.89ms 15v - 0.82ms 16v - 0.81ms I'm running these values on my RB20 Neo with 570cc Denso R35 stock jets and it's great. Also bought a set for my Legnum VR4, love these injectors!
    • Thanks for your reply,  Those blue/green wires running to the actuator aren't attached to anything, so I'm not sure how the central locking is still working. I will have to take a good look tomorrow, I don't have the car with me. After googling it seems like a pretty common aftermarket actuator which even uses the same green/blue wires the immobiliser required. i'll test everything tomorrow and if it's working i'll melt the solder, strip it, resolder and neaten it all up with some heat shrink. I don't have to understand it if it works hahaha I just don't want a fire/ short circuit. That R32 diagram looks more like a continuity chart? Can you make sense of this form the R34 manual? 10V is probably due to very flat battery, i'll recheck as well tomorrow, I did have to jump start it haha. Thanks again!  
    • So, COM doesn't mean comms. It means common. What common itself means will depend on the type of device. For a two directional actuator (ie, one that can push and pull on the same output rod) then the common will typically just be the earth connection. There will be at least 2 other wires. If you put 12V on one of the other wires, then the actuator will push. On the other 12V wire, it will pull. Can't quite make out what is going on with the wiring of your actuator. It appears to have several wires at the actuator plug, but there only appears to be 2 wires where its loom approaches the door control module, with at least one of the others cut off. I don't know these actuators off by heart. I'd have to look at a wiring diagram for one before knowing what the wires were about, and that's despite me having to replace one in my car not all that long ago. Just not interesting enough to have dedicated memory set aside for trivia like that any more. That actuator is an aftermarket one, not the original one, which probably died and was replaced. That might require some sort of bodge job on wiring to make it work. Although nothing should justify the bodginess of the bodge job done. As to the soldering job on the door module's loom plug. Ahhahhahaha. Yes, very nasty. Again, I cant tell you what any of those wires do. You'd need to study the R34 wiring diagram (if you can find one that shows the door module). I don't think I have any. I'd have to study the R32 diagram to start to understand what mine is doing, and again, even though I've had a problem with mine for the last 25 years (where it locks the passenger door when the driver's window reaches top or bottom of travel) I'm just not interested enough to try to to work it out. So long as it's not burning down, it's fine with me. Here's the R32 GTR diagram, which, confusingly, has rear door lock actuators and window motors on it!! As you can see, unless you understand the functions of the door lock timer and the power window amplifier, you'll never be able to work out how it works just from the diagram. I don't imagine that the R34 one is any better. Hopefully an R34 aware bod can help. FWIW, the two wires that are cut and joined look like they are both power supply - so hopefully it is not fatal to join them. The 10V you measured on the cut off free end of one of them is concerning. You'd expect 12V, and it might be the reason for the bodge job joining them together.
×
×
  • Create New...