Another cold start discussion....

I will start by saying I have read every thread on cold start issues and tried everything I can think of with no luck......

I have had a cold start issue every since I completed my current build. I have ignored it for a long time but decided to tackle it recently and just cant seem to find a solution.

On first start in the morning the car starts up perfectly. It will idle fine as long as I don't touch the gas or put it in drive or reverse. If I blip the throttle, it will rev up fine, but when the rpms come down, they just continue falling and the engine dies. If I put it in drive, it also dies. I can prevent this by pumping the throttle gently. After about 2 minutes...... everything is fine and it runs perfectly.

Other than this issue, everything is perfect. Trims, afr, idle, driveability........everything is fine.

I have tried everything recommended in other threads. Base running airflow, cranking fuel, idle timing, etc, etc. Nothing seems to help.

Any ideas appreciated..... I would like to solve this once and for all.

Attached is the tune I have been using for a while. I have tried changing all the things mentioned with no luck so for now I am back to running this one.

try [emc12199] normal high limit is -10 change that to a positive 10 see if it helps and can then lower it if its too high, also your idle spark table look at the .44 800rpm and below when idle starts to die it goes into this area and ur timing drops off into the minuses u can keep it higher so it dies and timing is there to keep it alive a bit longer (same to the coastdown table), if u have a log of it dying look at where the spark goes then u can see where to increase a bit, not sure how much these will help but worth a look

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Originally Posted by 07GTS

try [emc12199] normal high limit is -10 change that to a positive 10 see if it helps and can then lower it if its too high, also your idle spark table look at the .44 800rpm and below when idle starts to die it goes into this area and ur timing drops off into the minuses u can keep it higher so it dies and timing is there to keep it alive a bit longer (same to the coastdown table), if u have a log of it dying look at where the spark goes then u can see where to increase a bit, not sure how much these will help but worth a look

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Thanks for the suggestions.
I am going to look at these possibilities as soon as I have some time. Would that emc12199 table effect only cold start like that ? I have never played with those.

it will affect it all the time, ive only played with that table a bit since my stock settings arnt right, it allows the limits for adaptive correction so if u have say a error of 5g/s too much air it will only let u correct it by a max of this amount and if max is 1g/s then it wont be able to lower airflow, i found it to be a powerful table if its used right can help or hinder idle corrections

No real change with those suggestions. I now lowered the over and underspeed spark corrections but will have to wait again to see if it helps. Pain because the car has to be dead cold for testing.
This dam thing is driving me nuts.

also if u are ment to be SD it still dosnt look the be setup to fail maf properly so it may be taking a while to fail then when it does its ok but before its still a bit unknown ? it is set to mil first error but then the maf fail high 2 and low 1 need to be set and the high and low counts set to 1 and both tests set to 0 then it should fail instantly after cranking

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Originally Posted by 07GTS

also if u are ment to be SD it still dosnt look the be setup to fail maf properly so it may be taking a while to fail then when it does its ok but before its still a bit unknown ? it is set to mil first error but then the maf fail high 2 and low 1 need to be set and the high and low counts set to 1 and both tests set to 0 then it should fail instantly after cranking

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Car was actually run maf only for years, including with this setup. I just recently switched to a blended tune. It runs better this way but no change to this one issue I have.
I tried a couple more things this morning but no real change. After 2 or 3 starts I have to wait hours again to try anything else.

Strange thing is it starts right away, and idles fine as long as I don't touch the gas for a few minutes. Its not really the end of the world, but I would love to solve this issue.

ecm12153 u can adjust it for temp related correction at the moment colder is less correction u could try bringing that up a little see if it helps, same with the min air ECT multiplier in just the lower temp, maby add some more to the "throttle follower torque" under idle maby in the 400-600 range the 200 look enough also idle target speed 760rpm is ok but the in gear and p/n are much lower so if u put it in gear it will drop anyway maby try them a little closer if it dosnt push, could bump up the "min rpm ref" also maby 50 less then warm idle, also "under speed thr delay" change to 0 so it reacts straightaway, percent max/percent max brake maby add .5 - 1.0% more see if it helps, not sure if any of these will help but just putting some options out there encase u havnt tried them...

I think I'm finally on the right track. Thanks for all you suggestion......many I had already tried and some it tried with no real result.

This morning I decided to take another direction and made some changes to my EOIT settings. I cant be 100% until the morning, but after a almost dead cold start, it seems 90% better. I am hoping that is the main issue and tweaks to airflow and timing will have some effect now and I can get it perfect. I have never been so excited to solve an issue.( I hope). Spent so much time on this with no results previously.

sounds good i like it when u finally start sorting out issues and going in a forward direction, i have changed my EOIT quite a bit and keep it delayed even for cold start same as operating temps i think it has helped but it is a little leaner once running cos i think the ethanol is a little cold to fully ignite till it warms up a little but i can touch throttle no worries

Dead cold start this morning. A little surging in the idle but I can give it gas or shift into gear and it doesn't stall. Definitely huge improvement. Now I will recheck MAF and VE and fine tune that start with the previously mentioned table. Probably a little open loop changes to get it perfect. I really wouldn't have thought of EOIT to help this problem so much but sure glad I went there..........

yea always amazes me sometimes what can fix some issues and its usually the random "just see what this does" that ends up helping out, i always wondered with cams/eoit that if u inject just at the time when the exhaust pushes a little wave back into the manifold just as the intake valve is opening if it affects the pulse so ive always thought to inject idle after any possibility of this happening (if it does happen)

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Originally Posted by 07GTS

yea always amazes me sometimes what can fix some issues and its usually the random "just see what this does" that ends up helping out, i always wondered with cams/eoit that if u inject just at the time when the exhaust pushes a little wave back into the manifold just as the intake valve is opening if it affects the pulse so ive always thought to inject idle after any possibility of this happening (if it does happen)

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I really don't know enough about it and should learn. I delayed the injection until after the exhaust valve is closed, and it helped big time.

Just to update I can now say that my cold start problem is completely fixed after chasing it forever. EOIT was the answer.

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Originally Posted by realcanuk

Just to update I can now say that my cold start problem is completely fixed after chasing it forever. EOIT was the answer.

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Would you mind sharing old and new EOIT

Every thread I ever see never actually gives any numbers. They explain over and over but I dont learn that way.

Obviously they would be different depending on cam specs and valve events. I put the normal ect back to stock and changed the boundary so that it injects after the exhaust valve is closed at lower rpms.

Before

Attachment 80187


After

Attachment 80188

this is very handy info. thanks for sharing.

I need to study EOIT editing and its application with a large camshaft.

with early (2006-2008) E38 the only way ive got stable cold idle is by leaning the colder ECT and inlet valve temp areas of the open loop EQ value out. also the same areas in cranking FA stage 1 has helped before. later E38s seem fine but I cant get the early ones to idle with stock open loop EQ values. theyre miles too rich often commanding as low as 7.72:1AFR.

whilst the above always "works" ive always felt its slightly crude and there was a better way to achieve same result.

I often also make 600rpm and below spark table values for entire airmass the same number. this avoids as airmass increases while RPM falls the stock values will remove timing making it worse. ive also added timing as RPM falls eg. 1000rpm 15* 800rpm 17* 600rpm* 19* 400rpm and below 22*

Quote:

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Originally Posted by lukearmstrong1990

this is very handy info. thanks for sharing.

I need to study EOIT editing and its application with a large camshaft.

with early (2006-2008) E38 the only way ive got stable cold idle is by leaning the colder ECT and inlet valve temp areas of the open loop EQ value out. also the same areas in cranking FA stage 1 has helped before. later E38s seem fine but I cant get the early ones to idle with stock open loop EQ values. theyre miles too rich often commanding as low as 7.72:1AFR.

whilst the above always "works" ive always felt its slightly crude and there was a better way to achieve same result.

I often also make 600rpm and below spark table values for entire airmass the same number. this avoids as airmass increases while RPM falls the stock values will remove timing making it worse. ive also added timing as RPM falls eg. 1000rpm 15* 800rpm 17* 600rpm* 19* 400rpm and below 22*

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Not really the same problem. Mine would idle fine even dead cold. It would just die if I blipped the throttle or put it in gear for the first approx. 2 minutes. I tried everything imaginable without success until this.

where did you find the info on what EOIT is, what it does, data values and suggested edits vs application?

I have also found in A6 cars with decent camshafts garage shift tq management and tq reduction can cause stalling when selecting D or R from idle stand still. I now disable that

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Originally Posted by lukearmstrong1990

where did you find the info on what EOIT is, what it does, data values and suggested edits vs application?

I have also found in A6 cars with decent camshafts garage shift tq management and tq reduction can cause stalling when selecting D or R from idle stand still. I now disable that

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Read through this thread... lot of good info.

https://forum.hptuners.com/showthrea...ance-Requested