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Discussion Starter · #1 ·
Hi all, I’m running an Me221 on a turbo build. I’m having trouble with idle dip/stall.
The car is getting tuned on the 24th but I have to drive to get an MOT, then fit a new clutch and drive 300-500 miles to bed it in before the 24th.
So I know that I can tweek idle settings but since it’s getting tuned on the 24th I’m just after a quick fix to get me by till then.
It starts and idles fine on the base map. But returning to idle the car stalls most of the time.
Any tips??

thanks

Luke
 

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a few things to look at

tps calibration - you need to make sure the TPS, when shut, doesn't show the sensor over the % of the idle configuration. the idle valve runs with the tps under a small % (say 3% or 5) and with the engine range between 500 and say 1500.

whenever I do tps calibration on the me221, I use the built in MEITE tool to do the initial bit and then watch the TPS at max and min and see if it's bouncing or not. you may need to increase or decrease the 0 or 100 point voltage to get it stable.

and your pwm settings for the IACV should be the appropriate ones for your IACV valve, which changes between some years.. different frequencies.

put up a screenshot of the MEITE IDLE section and tell us more about your car.

if you can't be arsed doing any of that, reach out to DAI @ Valley 5s and he'll charge you a small fee for remote tuning. I've used his services before when I didn't understand it. Good guy.
 

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... and your pwm settings for the IACV should be the appropriate ones for your IACV valve
Yes, this is a good place to look. Sorry I don't speak ME221 but the MS equivalent might be "Dashpot Adder", which is a percentage added to the last known good setting for the idle air control valve, added whenever you lift off the throttle. That gives a bit extra idle air (mine is set at about 4%) to make sure the revs don't sink too low as you come to a stop. Better to catch it as the revs fall, have it enter idle a bit fast then settle down over a few seconds.
 

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the PWM frequency looks correct for an NB.

I'd have thought you should be in closed loop though. Lazy tuners.. are lazy.

Did you check your TPS calibration ? especially with the foot off the throttle. It shouldn't go over 3%. It ideally shouldn't go over 1%. If it does, you should recalibrate it (it's a menu option in Meite) and possibly set the Conditions TPS Max to 4% or 5%.

The way this is meant to work is the ECU detects the TPS is under the Condition tps X%, within the RPM range defined, it then starts the PWM output for the IACV. You've got an open loop setup so it can't give more PWM, it's got a hard-set PWM. [ In closed loop it would detect the falling idle and then adjust the PWM higher to run the IACV more and let more air in to maintain idle speed. ]

Another thing to consider, which is what I had, was I had a dying (but not quite dead) battery and that drained too much power when the engine spun down. If your car was 'fine' a few months ago but now the RTI is bad, and you didn't touch the engine or tune, that's something to consider.

The 'dashpot adder / extra load adder' is there but at 0%, but I'm not sure what that actually does.

If none of that works then I suggest you look at open loop.

And one last thing to consider, which is really a stopgap, look at undoing the idle air supply screw at the throttle body, say, half a turn or a whole turn.

Working with the Tune can be fun and IDLE tuning is harmless. Just back up your tune so you can revert your changes, if you're worried.
 

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Discussion Starter · #7 ·
Thanks for the advice, just to confirm I am still on a base map. I have only just finished the turbo build.
would I be better off in closed loop?
I won’t have much time this weekend to try things out unfortunately.
 

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Closed loop should be far superior.

Also your Idle Target RPM should be far more linear. say 1500 rpm in -20c to 750 rpm for 100c

Closed loop will actually use your target RPM table.
 

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Discussion Starter · #9 ·
Today I did a start up in Closed loop. TPS at idle was 0%.
Idle is sitting around 1200, the engine isn't warmed up. A blip of the throttle to 2000rpm and the revs fall. They would fall to 700 and quickly return to 1200.
So I take for a very short drive with only 5 or so stops. Each time the idle dips to approx 500 but did recover back to 1000 rpm. So I have a swing of 500 rpm. I'm letting the engine 'run down' before engaging the clutch so the drop isn't huge.

I think the extra load adder is for when running auxiliary items. Lights, fans etc. But there is a plus adder in MEITI but its called the CL RTI INC%. This is currently set at 6% for 2 secs so I could try to increase this % and dwell time.

MEITI says it adds this % to the open loop table.
 

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I'd also try this.. bump the 2 secs to 3.

Bump the min duty by a few points say from 20 to 22

unscrew the idle air valve half a turn



if none of these things help, check your battery voltage is still over 12.6 when the engine is off.
 

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I had exactly the same niggly problem, but on my megasquirt, as Martin points out above, you will find the resolution in the “dashpot adder” settings.
Try adding 5% then adjust from there depending on the result of the change.
This setting emulates the small damper fitted on the throttle stop that stops the throttle slamming shut.
 

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Discussion Starter · #13 ·
Better today, I increased the RTI dwell time to 3 secs and increased the min duty where the temp was currently at. The idle then only dipped to 900 so much better. So rather than go through the whole duty range I increased the RTI % by 2 percent. So went for another short test drive and it only stalled once. So still more work to do but should get me to the MOT and tuners much more comfortably.
 

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Discussion Starter · #14 ·
So I’m still really struggling. Cold start seems to be ok as per my last post. Today I started up to make sure everything was ok for the mot tomorrow. Once it’s warm it will be stable for a while but then it I’ll see afr go to 19 20 the revs drop and cut out.
It then wont start without throttle and the afr will now be at 16 17. I’ve put the whole idle target table at 1300 which it does sit at but it drops so much it stalls.
I’ve increased the idle PWM to 25 scaling down to 20. Which didn’t seem to have much affect.
Any last tips before I have to drive it properly tomorrow?
 

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Discussion Starter · #15 ·
Ok idle control valve opened by 1/2 a turn. Idle duty raised to a flat rate of 30.
For the few mins I had it at idle and blipping the throttle it still dipped but not below 1000rpm. So I’ll have to leave it there and keep my fingers crossed for tomorrow.
 

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Sounds like AFRs are at least part of the problem. If closed loop AFR is off then enabling it might help. Bumping up the VE in the cells around idle could also help in the short term. In my experience the idle stability degrades a lot above 16 AFR.


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if you log where in the map it's seeing 16s or higher, I recommend you just add some fuel there to get it down to at least 15, and then check again once it is warmed up. mapping should be done so it idles correctly warm then you configure the cold startup tables to give it the extra it needs. realistically if you want it to pass MOT you want it to idle very close to 14.7 so it sees the idle lamba get the average of 1.
 

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if you log where in the map it's seeing 16s or higher, I recommend you just add some fuel there to get it down to at least 15, and then check again once it is warmed up. mapping should be done so it idles correctly warm then you configure the cold startup tables to give it the extra it needs. realistically if you want it to pass MOT you want it to idle very close to 14.7 so it sees the idle lamba get the average of 1.
you don't even need to log, just look at the map and where the engine is sitting before it stalls at a silly AFR. add 5% ve, repeat until satisfied.
 

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Discussion Starter · #20 ·
MOT passed! I got lucky with the block settings I put in and had no dipping issues. I think the crazy AFR's were just as it was stalling and isn't an issue. It idles in the 14's.
So I'm very happy and looking forward to getting it tuned on Wednesday.
 
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