Coasting idle tune issue

[TheSlow1]

Im havin this issue with my new tune where when I am coasting with clutch pushed in the idle will drop down below 500rpms on occasion and it will pop a code. Sometimes the car will also stall out. Also when I come to a complete stop the idle will come back up to the commanded 900rpms. I know it is probably the dashpot or ISC that I need to adjust but looking for help as to which one

Thanks. Larry

 

[ski]

Installing a new tune will cause an erratic idle until the ECU re-learns the idle strategy, which may require up to 50 miles of driving.

 

[stkjock]

did you let the car re-learn the idle after you installed the tune?

ie- load, start, idle for 5 mins, turn on A/C, idle an additional 5 min

if not, then try that first

 

[TheSlow1]

I thought the car doesn't learn anything when the adaptive is turned off. ?

Additionally I can load my old tune and not have the issue. Then reload the new tune and the issue is still there

 

[stkjock]

I thought the car doesn't learn anything when the adaptive is turned off. ?

that's correct - I wouldn't have known that before as you didn't mention it.

I believe it's the dashpot that is needing adjustment

 

[TheSlow1]

That's what I'm thinking as well. However I have also read something about adding some
Timing to the closed throttle decel tables and or the idle spark table and that helping. I'm goin to take a look at both tonight when I get home. Just trying to get a bit of advice while I'm stuck at work without my computer

 

[BruceH]

All of my dashpots are adjusted. I think the decay rate will help the most. It took alot of experimentation to get my motor where it is driveability wise. I made at least 50 flashes changing one thing at a time until it was perfect. Because of that I can't remember what worked the best for decel rpms.

IIRC Dashpot decay made the most difference for what you are describing. ISC dashpot gain is the only thing I changed in the scalar. Is your coasting idle set to the same rpm as idle?

If you want to do some comparison I can email my dashpot values. I came up with most of the values when I had 127300 cams which are the same as yours except for more lift.

 

[stkjock]

Bruce now that u say decay, I think u r dead on, as I recall that is what Lund adjusted in my tune when I had a similar issue.

 

[TheSlow1]

well I checked a few more things on the tune tonight real quick and actually adjusted my spark for decel. I added some timing into it so that its not such a transition from my borderline spark to the decel spark. This seemed to help allot but I will need to go out and drive the car more to really find out. I do plan on dialing in my dashpot and decay rate some in the future but as of right now the car comes down off rpms really well and doesn't stall so I'm fine with it. I have some more adjustments to make on my timing in the midrange and then i'll be able to get the car on a dyno and finalize everything up top.

The thing I love about the PRP and the forums is I can log and compare so many different things and as long as I do some research before hand and don't try to do to much all at once I continuously make progress on my tune. As it sits right now this tune i'm creating is allot safer, and more responsive then the tune I paid for done on a dyno.

Also feel free to send me any files you think may help for comparisons. [email protected] is my email. I have a tune that I use just for comparing things

 

[BruceH]

Dashpot and idle files sent.

 

[TheSlow1]

Thanks for the files. I'll have to check those out tomorrow. I have however verified that the coasting idle is alloy better now from commanding a higher spark for decel. The car no longer dips below the commanded idle rpm it more or less comes down nice and smoothly and just rests at 900rpms. I'm thinking the transition from the commanded spark while in gear to the spark for decel was so great that the car would try to jump down to fast and miss the targeted spark then have to try to compensate.

Maybe not hat was actually happening but it sounds good in theory and the car is running better then ever. Few more tweaks and it's time for the dyno to cleanup the big end and verify power