Help with sporadic high idle

[Sla90lx]

It's scalar IAC - TPS percent for closed throttle

[EagleMark]

Right, but you said volts and it's 1.17 %.

First thing is get rid of error codes, then try data log again.

[Sla90lx]

Cleared codes and went for warm up drive. wasn't idling as high but still no idle mode.

Chris.

[EagleMark]

That is strange? I just looked at some other data logs and it was working! Never have dealt with that before and not sure where to look for issues? Maybe someone else has an idea?

[Sla90lx]

Anyone else have an idea what to look for? Everything I see in datalog is shows it should be in idle mode but its not. When it does go to idle mode the IAC drops down and runs about 700 rpms. I've even been setting in gear and have seen it go in and out but don't see any related values vary with. It's got me stumped.
Chris.

[EagleMark]

I thought that flag was based on TPS and VSS? But it may be more? Looking at yourt data... again... it does not look like idle data of a stock engine?

You never answered this?

But this thing has very low MAP kpa at idle? Hope it's a big cam?

Unless that engine has a big cam change? Then something is wrong as idle is 60 MAP kpa... stock is closer to 35 MAP kpa.

If it has a cam? Look at this bin, it is your bin with more spark at idle, more RPM at idle and BLM cells changed to reflect engine/cam changes. Learn to use the compare featuer of TunerPro to find what I did. These changes will get idle more under control and lower MAP kpa when in idle and hopefully see you Idle flag work right.

[Sla90lx]

Thanks, ill take a look. The motor is totally stock except for cam wich is probably overkill. .216 .223 @ .050. I know mechanically its solid with new everything except knock sensor and esc mod. But from day one this thing has been a dog with no throttle response what so ever and about ten mpgs. I know the timing has got to be part of my problem but I haven't really fooled with that yet wanting to get ve straight first. I feel I'm at that point. This morning's log looked damn good +/- 2 blms.

Chris.

[Sla90lx]

I see that you changed the blm cells more around my idle. Would you explain those two as there is no parameter comments for them.
Chris.

[ony]

map mph thresah hold and there is another mph threash hold but I forgotet, their scalers,mph trhes hold for idle.

[EagleMark]

Thanks, ill take a look. The motor is totally stock except for cam wich is probably overkill. .216 .223 @ .050. I know mechanically its solid with new everything except knock sensor and esc mod. But from day one this thing has been a dog with no throttle response what so ever and about ten mpgs. I know the timing has got to be part of my problem but I haven't really fooled with that yet wanting to get ve straight first. I feel I'm at that point. This morning's log looked damn good +/- 2 blms.

Chris.

With that cam and stock chip it should be a dog and your lucky your getting 10 MPG!

Well with the spark I added for idle it should be much better with that cam at idle only. Now I know you have been working on VE and done a great job on the table. But after you get a complete spark table adjusted for performance and that cam? It will need to be done again.

I see that you changed the blm cells more around my idle. Would you explain those two as there is no parameter comments for them.
Chris.

BLM is Block Learn Mode and is Long Term Fuel Trim. It's set from INT = Short Term Fuel Trim. With that cam your overlapping the learned cells or not even in the right cells. Take the MAP and RPM and create a ... never mind, look at this.

And ony is probably correct in that a MAP threshold for idle is not being met. With the little RPM and lot of spark I added at idle the MAP should get a lot lower.

[Sla90lx]

I understand blm and int are short and long term. What I don't know is the meaning of cell boundaries. Can you point to some threads that explain this in depth? I agree with Map threshold for idle but have not found anything in the bin yet to support this. I am committed to learning this and know that it will be a long road to travel. I fully expect to make hundreds of changes before all is said and done and am up for the task. I've even purchased both a Greg Banish's books and have enjoyed them so far(thanks for that one.) I'm about to go for a drive and see how these changes affect things.

Thanks, Chris.

[Sla90lx]

Never mind the request, finding plenty info out there. Google is my friend!

Chris.

[Sla90lx]

Just an up date on idle mode. I bumped TPS% for idle up to 3% from 1.17 and haven't had a problem with staying in idle mode since. My BLMs are consistent 27-28 cruising from off idle to 75 on hwy. I need to drop fuel at idle now with the BLM cell boundary changes but I don't think that will take too long. So it looks like next up for me is to start playing with the timing I guess.
Thanks for the help, Chris.

[84Elky]

This one is driving me nuts! I've been working on getting my VE table in line and making good progress but my idle will sometimes be ridiculously high when I come to a stop. I've just noticed today that when this happens the sensor data in TP shows idle mode to be off idle. My TPS data show 0.53 volts & tps% 1 or sometimes 0.51 & 0 with VSS @0, but IAC counts sometime as high as 100. When it does work properly, I've seen it go to idle mode as soon as VSS is below 4 and the IAC counts drop to 10-15. I have short logs of when it does both if anyone can help, this is a 7747 with $42 mask.

Thanks,Chris.

It's possible the VSS signal to the ECM is > 0 MPH when the problem occurs. That can occur with loose wiring, poor ground, etc. Bottom line, for most OBD1 ECMs VSS must report absolutely 0 MPH or will not be considered at idle. The fact that is works sometimes and not others indicates a possible inconcistent VSS reporting issue to the ECM. Additoinally, most code has a minimum TPS value that determines when idle is being considered. Might check that value. For example, for '7730, it's 0.78% and below.