chrome v2 high idle problem with a/c on

[mcgiver50]

Hi everyone, I have a 95 vr4 that i'v built from the ground up and am having problem with fast idle ever since i installed chrome ecu. When i drive the car coming to a stop it hangs on fast idle as long as the car is rolling. It does it a little with a/c off...barely noticeable...but with a/c on or heater /defrost(when a/c compressor is engaged) it sticks on around 1500 rpm until i come to a complete stop then after 3-4 seconds will return to my target idle rpm of 825. I have set idle biss screw with evoscan and seems to idle good at a standstill a/c on or off. I ohms checked iscv and they seemed to be within specs. I don't recall it doing this with the stock ecu. I tried adjusting some of the tables for idle steps a/c on but nothing seemed to make any difference...not sure if i should have reset ecu every time between those changes though. Does anyone know exactly what those tables do and the proper way to adjust them? or as i think i read somewhere else that it's supposed to be that way? If so is it adjustable? Thanks in advance for help or insight you could give me, Roger.

[Unlogic]

If I'm not mistaken the tables in the ECU are set to a idle of around 1500 when the engine is cold and the AC is turned on. If you have a look in the ROM withe EcuFlash you'll find tables with all these values, it's a very simple tweak.

[Dougal]

Below are the tables you probably want to look at.

One for AC on and the other for AC off.

I personally leave the cells under a warmed up engine operating temp as they are (to assist in warm up period)

Does the RPM hang when engine is fully warmed up? Id so then these table may not help bring that down.

Some other issue perhaps FIAV? (Fast Idle Air Valve). The FIAV are known to not perform as well as they used to over years and years of hot/cool cycles.

Target idel AC on AC off.jpg

Other thing that bumps idle up is the power steering switch being on (when your turning stering wheel the idle RPM bumps up a bit)
You can log that in Evoscan to see if its switched on when this issue is happening when its hanging at 1500rpm

[mcgiver50]

If I'm not mistaken the tables in the ECU are set to a idle of around 1500 when the engine is cold and the AC is turned on. If you have a look in the ROM withe EcuFlash you'll find tables with all these values, it's a very simple tweak.

thanks unlogic for the reply...i am familiar with those tables and have successfully been able to adjust them. the problem is the car idles fine as long as i am not moving, i can rev it up at a standstill with a/c on or off and it comes right back down to either target idle rpm depending whether a/c is on or off. if i am driving the car even in a parking lot and i give it gas and move the car forward it hangs at around 1500 rpm until i stop completely, even if i am only moving 2mph it hangs high. i logged idle steps at 77 while this is happening. i think it might have something to do with idle steps a/c on table, but i can't seem to get it to change this problem when i adjust that table. any ideas? thanks for your help!

[mcgiver50]

Below are the tables you probably want to look at.

One for AC on and the other for AC off.

I personally leave the cells under a warmed up engine operating temp as they are (to assist in warm up period)

Does the RPM hang when engine is fully warmed up? Id so then these table may not help bring that down.

Some other issue perhaps FIAV? (Fast Idle Air Valve). The FIAV are known to not perform as well as they used to over years and years of hot/cool cycles.

Target idel AC on AC off.jpg

Other thing that bumps idle up is the power steering switch being on (when your turning stering wheel the idle RPM bumps up a bit)
You can log that in Evoscan to see if its switched on when this issue is happening when its hanging at 1500rpm

thanks dougal...i have set idle tables and it seems to work correctly as long as the car is at a standstill. i haven't checked fiav but was not a problem with stock computer and if a/c compressor is off it works fine. steering bump up seems to work fine and can see that with evoscan. i logged 77 steps on iscv when this happening but don't know how it gets there. thanks for your help!

[DrGonzo]

Sounds like you tps is out of adjustment. I know a lot of people have this same issue if there TPS is set less than like 12-13% when closed. Try adjusting your TPS and see if that corrects the issues.

[mcgiver50]

Sounds like you tps is out of adjustment. I know a lot of people have this same issue if there TPS is set less than like 12-13% when closed. Try adjusting your TPS and see if that corrects the issues.

Thanks DrGonzo but i've done that and have logged it on evoscan...12.94 and the idle switch is working. i think if it was the tps switch out of adjustment it would do it all the time whether the a/c compressor was engaged or not. it's very consistent on what it does i just don't know how to or if i can adjust it...but does every obd2 3s car do this? (chrome ecu). i'm probably missing something, thanks for your help DrGonzo!

[Dougal]

Is your idle switch coming back on at the point that its hanging up the RPM?

Do some datalogging and log idle position switch to see it is coming back on or not.

As far as I recall setting the idle position which is adjusted via TPS however can be affected by how far out the BISS screw is out (letting in more air to the motor)

As you mentioned the stock ECU does not do this but its worth a look as i suspect that the Idle switch is not switching back on and the amount fuel and air entering the motor at that point is keeping the motor idling higher than it should.

Idle pos switch.jpg

[mcgiver50]

Is your idle switch coming back on at the point that its hanging up the RPM?

Do some datalogging and log idle position switch to see it is coming back on or not.

As far as I recall setting the idle position which is adjusted via TPS however can be affected by how far out the BISS screw is out (letting in more air to the motor)

As you mentioned the stock ECU does not do this but its worth a look as i suspect that the Idle switch is not switching back on and the amount fuel and air entering the motor at that point is keeping the motor idling higher than it should.

Idle pos switch.jpg

Hi Dougal, I did some datalogging today and i think the idle switch is working. I noticed while looking at the logs that the timing advances as i come to a stop with a/c on, almost 10 degrees more than the target timing table is calling for, and then after i come to a stop the timing starts to go down back to target number as the idle settles down to target speed at the same time. I've played with iscv tables again but nothing seems to make any difference with the idle hang. Could this be some issue with a timing table? It only does this with the a/c on, idles near perfect when car is not moving whether the a/c is on or off. With a/c off idle does not hang. Has anybody else with chromed v2 or 99 vr4 noticed this with their car. It's a little annoying especially when cold. I'll send a section of the datalog showing me coming to a gradual stop. What do you think? Thanks Dougal.

[Dougal]

Hi Dougal, I did some datalogging today and i think the idle switch is working. I noticed while looking at the logs that the timing advances as i come to a stop with a/c on, almost 10 degrees more than the target timing table is calling for, and then after i come to a stop the timing starts to go down back to target number as the idle settles down to target speed at the same time. I've played with iscv tables again but nothing seems to make any difference with the idle hang. Could this be some issue with a timing table? It only does this with the a/c on, idles near perfect when car is not moving whether the a/c is on or off. With a/c off idle does not hang. Has anybody else with chromed v2 or 99 vr4 noticed this with their car. It's a little annoying especially when cold. I'll send a section of the datalog showing me coming to a gradual stop. What do you think? Thanks Dougal.

Hi Mate,

I have tried a couple of times to open your datalog but have not been successful
I can see its in Open document format and whilst I am using Openoffice and it should read it is not.
Can you save this in .csv file format and reattach?