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Hondata S300 & Cold Start

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Evening guys,

I ran into an issue with cold start.

Engine: B18CR

IACV: Connected

Setup: Open Loop

IAT Sensor: Connected

ECT Temp Approx: 30c

When i start the engine it goes up around 900-1000pm. Then around 2:45-3:00 minute the idle fluctuates to 500rpm and died. Had to restart again and kept putting my foot. There were some cases where i didn't have to hold my foot and the idling was around 1000rpm.

Around the 6th minute, things got better.

Around the 18th minute, the water temp is close to the middle point and reading around 88c on the Hondata. Fan kicks in just after that around 94c.

Once the car is hot, i didn't encounter any issues. Only cold starts regardless day or night.

Here i attached the parameters, which i think might need some adjustments. Just need some help where should

i fiddle around first before anything else.

I have tried adding and reducing the percentages on the post start adjustment and it didnt work.

I tried changing the rpm level at the idle vs ECT to make it hold longer at the 3 minutes (based on water temp) still the rpm dropped.

I thought of adjusting the cranking fuel this time around and leave the rest alone.

Do let me know what you guys have in mind. Cheers.



Attached Files


If the issue is after the engine has been running for 2:45-3:00 minutes it is unlikely to be the post start enrichment as this would of decayed by then, also along with any crank enrichment.

A couple of questions for you.

A: What is your Lambda at this point when it start to fluctuate

B: What are your fuel compensations setup as, if you can put up a screen shot or attach your map

C: Have you tried increasing the IAC Duty Cycle using the slide bar

Try raising your rpm idle from 700, to match your minimum idle speed of 850, your telling the computer you want a minimum of 850 but are requesting 700 once warmed up. This could be a reason why its acting up. Try 850 and see what happens.

https://www.hondata.com/help/smanager/index.html?contents.htm follow these steps and you should be good.

Hey Chris@STM,

I'll start the car again tomorrow and see how it goes. Will feed you more infos.

At the moment the slide bar is between decrease to normal. Will increase it tomorrow to the middle or further up a bit. (so far i tried pushing it up and down and the idle starts to go up and down. so far it's working fine)

I'm trying to think what is actually cutting off the rpm level that particular time duration

2:45-3:00 minute. I managed to jot down some datas during my last troubleshooting.

At around the mentioned time, my ECT was around 48c and the idle rpm on stationary

setting ECT vs Idle Speed was 1300 for 41c. It dipped to around 500-600rpm.

Hey Tommy,

I'll check out the "setting the idle" again. At the moment i set the minimum idle speed to 1100rpm.

I apologize. The screen capture was from the stock P30 parameters. i was at work.

Thanks guys. Will update soon.



Evening guys,

So what i did earlier today before cranking the car, i added 30% of the post fuel adjustment (pix 003). Increased the IAC duty cycle to 3/4 of the slide bar (pix 004). I did not change the minimum idle speed.

Connected the LM-2 and switched on the logworks. Today was slightly cold(skin cold) after the rain. ECT was around 38c.

After i started the car, the rpm was highish around 1300-1400rpm and stable. Then came the gremlin again, at around 2:45 minute, the rpm dropped around 880-770rpm (pix 007). Car did not die and was low on idle. I let it run for another 2 more minutes (in total 5 minutes). I switched off the car and restarted it again, the rpm was around 950 range. I let the engine run for a good another 8 minutes and it just maintained at that rpm and the fluctuating afr reading.

I was going through the parameters and my TPS fuel cutoff was still unchanged. Not sure if this is part of the solution (pix 005)

Here i attached the low fuel map (pix 006).

To sum-up today's short trial and error, rpm was fairly high compared to my previous 500ish rpm. No error codes on the Hondata.

Not sure what was cutting the idle rev short at 2:45 minute.

Have a good weekend guys.



Attached Files

That is running seriously lean after your indicated point, picture 7, this will cause all of your oscillation as it looks like your cold start map is lean.

The pictures that you have posted up are related to your start up but not your cold start, it looks like you are missing a map somewhere that needs adjusted.

Agree with Chris250, I would check and adjust your warm up enrichment maps. These can be found under "Fuel Compensation" and look like the screen shot I have attached, you might find that at your problem area you have a dip in enrichment percentage causing your lean mixture and stalling issue.

Attached Files

Your map looks kinda funky, I believe at 245 is probably when your ect fuel and timing trim is decreasing. You should tune the fuel map First then tune cold and warm starts. What basemap did you start off with?


I am still running on primary map on tps setup all the way. Did some reading somewhere on the Hondata forum to fix this issue (maybe) is to run map on the primary and let the secondary run the tps from 1500rpm onwards. By the way this car runs on itbs so i havent run map yet since day 1 with the trumpets. Map sensor is connected by the way if you are wondering. Since you mentioned the missing map, i might put it on my last resort plan.




I have not edited any of the ones in the fuel compensation area. Only in the idle parameter (idle speed vs coolant).

I'll give it a try and log it again this weekend. I'll try to even out the correction as the temp goes up and see if it holds.

This time i might also monitor the air temp closely.

Is it true that any of the compensation area that has been edited needs the car to be restarted again for the new config to take effect?




I'll tell you the long story next time (smiles). Let me just sum it up. Car has been running with itbs since last September. Between September and November we had many runs on the dyno. Started with the itb.skl map and i made some changes to match the car. 1.8 B18CR with 48mm Jenveys and other mild modded toys.

Made some descent power for a street driven. Tuned slightly rich and so far no crazy knocks. So the only thing left is this little sluggish idling gremlin. Once its hot, it's good to go.

Yeah, the funky map was the only time i could start the car. There is a write-up on this on the hondata website about running slightly rich and etc. i did fooled around with other maps and i had difficulties. Plenty of trial and error setups (physical) to be honest.

Attached is the pic of the car. I posted on the other thread but no worries.

Just an old classic with a better heart.



Attached Files
  • 12072598-10153771909074683-4941346713436763069-n.jpg
  • Attachments may only be downloaded by paid Gold members. Read more about becoming a Gold member here.

If your still having the issue add a log and file...

this looks interesting... :)

I see now I didnt notice the TPS as load at first glance, how does your timing map look like?

Hey Tommy,

Attached is the map.



Attached Files

sorry meant the smanger file it self and a the recorded log... :)

Howzit goin' guys?

Been away for a bit. Was busy with work.

Anyways, some of the things that i have done the last 2 weekends:

- revamped the entire vacuum system. i had a small vacuum log before and this time i have added an extension to separate the FRP, IACV, brake booster, itbs and map. So basically i have 2 vacuum logs now

- to those wondering if i have any brake issues, no i dont have so far

- deducted a good 10-15% of fuel from water temp compensation at the fuel compensation parameter on low engine load

- reduced my idling rpm at the parameters as close as 1150-1250

- did not touch the fuel map low area

- no added fuel on cranking and post start fuel adjustment

The result, the "cut off" at 2:45 is gone. I had to do 3 times on 3 different days (leave the car entirely cold and start it in the morning) just to be sure. I am still using the IACV and still intact on the vacuum log. So the gremlin is gone (yay!). I suspected it was not the IACV but maybe the fuel correction was at fault here. But i cannot relate on the ECT reading vs water temp correction as at 2:45 it was not close to either the stated ECT temp on the Hondata.

So now the car starts with just 1 key turn away. I watched the ECT/IAT and RPM closely. It starts around 750ish and goes up around 1050 around the 10th minute. Once the engine has properly warmed up, no issues driving it around. I purposely step and release the accelerator, the rpm goes up and down and back to around 1000. No dipping and low idle.

But, i think the fueling is still rich at idle. Sorry i did not log it. Was just looking on the Innovate screen. It was around 11.5 AFR.. I can smell the stench of fuel in my nose.

I plan to deduct more on the water temp correction. Maybe this time around i will reduce some of the fueling on the low map idle area too. I just feel the car felt "cold" around the 3rd and 5th minute which makes driving to the local deli a bit frustrating. It does not "roar" like a normal car which has higher rpm at start and stables at around 950.

The last couple of weeks i have been watching https://www.hpacademy.com/previous-webinars/tuning-cold-start/ .

It is around 1hr 15minutes. Honestly i watched this 3 times just to understand how complex can this be on a modded engine. I think i spent a lot of time on just this issue alone.

I think i am almost there. Let me see what i can do and update you guys again. By the way if you are reading this, thanks Andre, the video was good and cleared up most of the definition issues i had.



Morning All,

I am taking a day off tomorrow and i am heading to the dyno center.

My plan is to change the injector dead times and check to see

if my AFR reading is on the safe level throughout the rpm range. Last dyno

run was end of last year.

Other than that i plan to spend some time after the dyno to improve the

cold start issue. Would be great if i can get some feedback and opinion

for my previous long-winded post to see if i can improve things out.

Thanks in advance.


Good day all,

The dyno plan did not happen last Friday. Car was strapped and was ready to go.

The Hondata S300 v2(red board) had problems. Did all the steps to revive it but failed.

I couldn't upload the new calibration. Erased the ECU close to 10 times. Made all

the so-called checking of connections, battery, using the old and newer smanager,

changed laptops and etc. After 4 hours i stopped, got a spare unit from a friend and

drove home. Frustrating day.

Contacted Hondata and apparently there was some battery issues with the

old versions. Anyways, i hope to get the new v3 (white board) soon and get

it on the dyno again. Used the v2 since mid 2013 and finally it gave way.


Got a used USDM P27 ECU with a new S300 v3. So went to the dyno yesterday.

I have replied on the other thread on the injector latency. It was rich.

Had to touch up the map entirely.

Regarding the the cold start, i tried to lean it a bit at the low percentages

of the map. There was a few times i couldn't start the car. The ECT compensation

has been changed also. I will see the next couple of times see if i can start

the car better this time around both during a cold or hot day.

Have a good day guys.


Hi Haz,

As I replied in your other thread, the change of dead times will have thrown all fuel related tables out, you should be able to work your way through them all pretty quickly as it's looking like the S300 is a second home for you now :)

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