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Poor Idle


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Quick summary:

Car runs on e85 with large injectors, I believe this is the cause for the poor idle.

Had the car retuned to compensate for the injector low pulse width data previously, still not 100%

The problem: Idle does jump around a little, I don't expect a factory idle but I would like to try and improve it as much as possible.

Main problem is when I rev the engine when it returns to idle it goes far below. Idle is set to around 1200rpm and it goes down as low as 700rpm. When the car is fully warmed it doesn't go as low, probably only to 1000rpm or so. Log attached at approx 60 degrees which I believe should be warm enough for the car to run great.

Also, the idle is set for 1300-1200 rpm but it never hits these figures and I'm unsure why.



If anyone could give me a list of things to try to improve the idle and stop it dropping so low when I rev the engine, that would be fantastic. Alternatively, if this requires detailed tuning and you know of someone who can remotely tune the car (just the idle) I'm all ears!


Thank you!

poor returning to idle.llg


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Ok, idle speed control is not working at all in your log.  It looks like there is a problem with the speed lockout in the old firmware that you are using.  

So first step, update to the latest firmware.  Here is a video guide: https://www.youtube.com/watch?v=u54915wuLYc&t=1s

After that set the speed lockout to driven wheel and 2kmh.  Also change the RPM lockout to 500.  Do us another log after those changes.


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A number around there 2kmh works best in most cases.  Basically you dont want the idle control to work when the car is coasting.  For instance during over-run down a hill your foot is off the pedal but the RPM is higher than normal so the idle control will close the throttle trying to bring the RPM down.  Then as soon as you press in the clucth the engine will stall because the throttle cant open quick enough.  To cover your "coasting in neutral" scenario your throttle target table and idle base position table need to be well set up so that when idle control is not active the throttle is still held in a reasonable starting position to achieve close to normal idle RPM.



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Okay I literally only had 2 minutes with the car tonight, and I made the changes you suggested, however I haven't had time to update the firmware. I will do that tomorrow.

But from the changes made, I couldn't select the speed lockout as you mentioned the firmware is old, but I could change the other settings.

The idle was much improved, however if I touched the throttle the engine would rev (seemed way more responsive), it would then hold the revs for a matter of seconds, and then drop all the way down and try to stall. The first couple of times it did stall but from the log I've attached it didn't quite stall. A step in the right direction but something still isn't right. I noticed on my AFR that it went very lean when it almost stalled.




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I think you've got a combination of slightly laggy ethrottle settings and an idle setup that is very low ign angle with a big throttle opening. 

You can have idle with low throttle opening (1-2%) and lots (20 ish or just over) of timing, or lots of throttle (5-6%) and really low timing (5-8), or any combination in between, and still get idle at the same rpm. 

You currently have a pretty wide throttle opening and hardly any timing (8 deg at normal idle). At this low of an ignition angle you need a lot of throttle angle change to get any additional HP to pull out of a stall, but with a throttle opening this wide you should be able to have a lot of impact using ignition idle control. To fix the stalling, try editing your ignition idle table so that instead of it reading 7,13,14,15,15 on the high side, it reads 7,13,17,19,21. this will make it add timing more aggressively to increase RPM when its below idle target.

regarding the throttle hang side of things, it looks like your ethrottel PID settings arent that sensitive to low amounts of error - eg if its only 1% out from target it takes 2-3 seconds to correct. It would be nice to make this more aggressive and fix this "properly", but you can work around it a bit just by zeroing out the 0% AP row of your ethrottle table for everythign above 1400RPM.


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Thank you for the reply cj.

I will try your suggestions tonight.

I must say I'm rather disappointed that I've taken the car to two different dyno tuners here in Perth, one that specialised with link ecu's and the car has never run great (aside from onboost).

I will play around with what you suggested, however does link offer any remote tuning services (obviously don't mind paying), if I can't manage to get this right myself?

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Okay, so I made the changes in two stages. Firstly I changed the timing and ran the car, then I kept the timing changes and made the PID setting changes and ran the car again.


From just the timing changes, I thought this had fixed the car, the idle was very good. But then it stalled again, the only time it stalled is when the rev's hanged for a few seconds, then just dropped. Refer to log 1 attached

Once I made the PID changes, the idle was terrible. Bouncing up and down nonstop even when I didn't touch the throttle. I have attached log 2 and the map showing the changes I made, perhaps I made the changes incorrectly?


Really appreciate the help guys.




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Please update your firmware before you mess around anymore.  Yours is over 3 years old and there have been many changes and fixes to idle control since.  Your log 1 looks like it is mostly ok, the stall is caused by the idle ignition table suddenly turning on at 1500RPM and pulling 25deg out.

Update firmware, do another log with the PID back how it was in log 1.  I think we will need to adjust either the main ignition table or the idle ignition table so that there isnt such a big difference between the two, but Id rather work with current firmware that I know better.

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Totally forgot about the firmware! Okay so I updated it and then did two logs. One with the ethrottle as it has always been, and one with the ethrottle set to 0. Setting the ethrottle to 0 doesn't do the idle any favours, it makes it really bad.

With log 1, the idle is good but it still tries to stall when I give the throttle a blip

Log 2, this is worse than log 1. Doesn't idle well.

Can't stress how much I appreciate the help guys!

Firmware update - log 1.llg

firmware update - log 2 ethrottle set to 0.llg

map for log 1.pclr

map for log 2.pclr

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@Jenno007 you're dead right that your idle control timing is a big part of your problem. The other part is understanding all the numbers that add up to what the ecu uses for its "ethrottle target".

First up, idle timing:

the idle timing doesnt really "take away" 24 degrees of timing. What it does is throw out your ign1 table, and use its own idle table when ign idle control is active. If you look at ignition>ignition idle table, you will see the values that it will use for ign angle when it is active. The top axis is "current RPM relative to target RPM". So looking at this, when you are on idle target, (0 error column), you will have 8 deg of ignition. When you are 500 or more RPM above idle target, you will run at 4deg ignition - which is probably not enough to keep it running hence the near stalling condition. Now from a dynamic viewpoint, when you RPM is dropping but its above your 1500RPM ign idle lockout, you run at your ign1 tabel values (about 29deg), and beacuse of some quirks in your ethrottle config which i'll get to later, about 5% open throttle (hence the slow rate of rpm drop). Now at some point you drop to 1499RPM and ign idle kicks in, and your ign angle changes from 29 deg from ign1 table to "you're 299RPM over the 1200 RPM target, I need to drag that RPM down by making ign advance only 4deg". your ign control values for "above target" are really low, so it basially takes away all power from your engine until you get down to 1200rpm, then it tries to "catch"  it when you drop under 1200RPM by ramping up your ign angle to the values on the right on the ign idle target.  Making the right hand "catch" values higher has helped but is a bit like an ambulance at the bottom of the cliff. To "fix" this properly you need to adjust your ign table and ign idle values so that there is a much more gradual transition from the main ign1 table values, to those in your ign idle table. Before we do this though, id suggest you decide what angle you want it to idle at. most engines OEM are between 10 and 20 deg. 15 is probably a good number if you have no idea.  Note that things are going to get worse before they get better because with 15 deg at idle, your 5-6% ethrottle effective target is too high and you will idle at 1700 or something. 

First up, grab you ign1 table and add in a 1250 or 1300 rpm column. interpolate it horizontally if it doesnt do it for you. then set the values in the 1250 column for any MAP at 60 or below to the same as those in the 1000 column. This 1000 column is actually roughly set up correctly for a "normal" idle, but your 1200 target is too high to hit it. 

Now disable ign idle control, set your throttle idle control to open loop, and see how you go. it should now idle quite a bit higher. Change the idle base position throttle target value up or down until you get the idle value you want. Now set the 0 column of your ignition idle table to whatever value you are currently idling at - probably 15-16. (this should match your ign1 table value). Note that there is now effectively no "jump" when ign idle comes on or off. Now set the over and under column of ign idle table so it tapers up and down by probably 2 or 3 deg for each column. You may need to adjust the aggressiveness of the change rate in this table later but 2 deg per column is a good starting point. You can now enable ign idle control again but you shouldnt notice any change when you do.

Now with ethrottle idle still on open loop, sort out your idle base position table so that its the same shape your have now - roughly flat above 70-80deg ECT and 0.2 or 0.3 gain per 10 deg below that. Start from whatever position you used above to get the idle right, its probably 70-80deg if it was warm, and shape the table from here. Now see how it handles throttle blips now that the idle ign table isnt trying to stall it all the time.

Your ethrottle target is the next thing to understand before you turn it back to closed loop or make too many changes. 

The commanded TPS value ("ethrottle 1 target" in logs) is made up of:

the number in the ethrottle 1 taraget table "ethrottle 1 base target" PLUS

the idle base position number "ethrottle 1 ISC offset" PLUS

the calculated ethrottle closed loop idle adjustment "ethrottle 1 ISC CL trim"

So in your case, pretty much all of these values are 2% (give or take), but because there are 3 of them added together, your target TPS value is 6-7% all the time (not the 2.5-3% you think you have from the APS target table. co-incidentally, this is a very good reason not to use APS% as your fuel main target - the ECU is pretty much never actually giving you the TPS% target you asked for anyway. Some of these numbers stop being added in once you get above the various idle thresholds, some of them dont (or are seemingly on timers so they drop off a few seconds after you break idle threshold)

With a 15deg idle, you probably want your TPS to be between 3-4% at idle but you'll figure this out for your engine through trial and error, and for general driveability, you want it to get to 0 when you let off the throttle above say 3k. Once you have it idling nicely from the above process, open up a log and see what actual TPS/ethrottle target you are running at. write this down somewhere. From here on you can pretty much take any path you like as far as which of the ethrottle adjustments you make which sizes, as long as they add up to this 3-4% figure you need. (eg it makes no difference if you are 0% APS table with 3.5% base idle target, or the other way around). Just bear in mind that the APS% table can only be accurate to 0.5% but the idle base target can be accurate to 0.1% plus it can change with ECT, so you will need values in here for the colder ECT temps even if you have it at 0 for "normal". 

To tune the base idle table, let the car cool down compeltely, start it up, then start a log with idle target and current RPM visible. dont touch the throttle or anything else in the car, but just let it warm up, and as the ect gets to each 10 deg point exactly, bump ONLY that value in the idle base table up or down a coupel points at a time until you hit your target idle for that ECT. You need to be quite quick as you dont want it interpolating too much from the next cells if it gets a deg or 2 higher. Once you have that cell tuned, wait another 2 min and just let the idle go high/low until you get ECT up to the next 10 deg marker. 

Once you've run through all of this, post another log and pclr file please. still with ethrottle idle in open loop mode.



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  • 1 month later...

So it has been a long time, unfortunately I don't get much time with the car as it's kept in storage. I've managed to sort the idle out it's much smoother now!

I took this log today from a full cold start all the way to 90 degrees (when the thermostat is fully open).

The only downside is, when I blip throttle, there is quite a delay before the revs go up, and it isn't too smooth. Then the revs hang for a while before they come back down. Any ideas what could be causing this? I've attached the map and log. The car doesn't seem like stalling anymore though which is a plus.



after all ignition changes.llg

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so I've managed to get the idle really good, the only thing I note now is bad throttle response. When I put my foot on the throttle it goes really lean and then revs. I've looked into accel enrichment but wasn't sure what I was doing. Any help would be really appreciated!



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  • 10 months later...

Thanks to you CJ & AdamW, for trying to help to sort this car out - I now own this car after Jenno007 has done an amazing job building it.

I'm going to get Tokyo Motorsport in Perth to try and sort out the tune once an for all, as this is not something I want to mess with myself.  


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