Looking for help with improving idling/tune

[asumsatlil]

i have a 1989 vw golf 16vT running on ms2 v3. i run and drives, but i have trouble at idle, it goes up and down for a while and wont settle. i was wondering if someone could look over my tune and a log to see where i can improve it, or upgrades i can make.

[asumsatlil]

another log

[turbo conversion]

From what I see you are running batch fire, most batch fire installs like to idle in the low to mid 13 afr range for the most part.

You really need a wide band o2 sensor to do any serious tuning, I am assuming you don't have one looking at your msq (it is disabled).

David

[asumsatlil]

i have a aem wideband sensor, i thought i had it enabled. i'll look at it again, i'll try to get it to idle with 13 afr then and see if that helps.

[turbo conversion]

i have a aem wideband sensor, i thought i had it enabled. i'll look at it again, i'll try to get it to idle with 13 afr then and see if that helps.

I looked at your data logs and the o2 sensor is working, not sure why the msq shows disable.

Can you post a data log with the engine idling with out moving the throttle?

David

[Hahns5.2]

No IAC? Gonna be a bit of a pain to get a consistent idle out of it without one. Looks like your base timing is 12º and you're adding about 15º with idle advance, which is quite a bit. I'd suggest making your idle advance curve to be a constant slope and have it end at your target RPM, so you steadily add timing as the RPMs drop below your target. Your TPS is also quite noisy, you're constantly exceeding the idle advance threshold, and the fluctuating RPMs also cause the MAP to exceed the threshold as well. Also add more fuel to the VE table, looks pretty lean.

[asumsatlil]

yeah i need to get an iac, i been driving with out one for about a year or so with the current tune. of course it runs alright, i got some free time so i'm trying to make it more refined. The TPS has always been quite noisy, i put twisted shielded pair cable in to try and fix it, its not as bad as it was. i made a few adjustments, after i rev it up it seem alot softer then it drops back down to idle, instead of dropping hard and shooting backup again. it still might need some more work though. the afr seems a bit low, but the car has a habit of stalling out when i rev it up and let it drop back down.

[turbo conversion]

IAC is awesome but you can and should get a stable idle first and you can do it with just a throttle stop.

Set all the timing, afr and ve cells in the idle area the same.

Increase VE numbers by say 2 or 3 all around your idle area.

Get the engine to operating temperature and set the throttle stop to desired rpm.

Once you get a pretty good idle you can fine tune the cells.

Once you achieve this, setting up an IAC will be a piece of cake.

Of course until the engine is warm it will suck.

David

[asumsatlil]

this may seem like a dumb question. my car came with a iac and a cold start valve, could i just use the cold start valve and wire it to the iac on the megasquirt? i'm assuming the cold start valve is like a pwm on/off valve. or possibly using both?
Part numbers: IAC 8857179, cold start valve 067906171

i've had the car idling and driving for over a year now, the tunes not perfect but works. the idle is a lot better now, i just gotta wait till it warms up till about 130F before it will idle properly.

[turbo conversion]

The cold start valve injects more fuel on a cold start, it can not be used for idle control

You should be able to use the stock IACV you just need to wire it to the MS.

If you do not have a very stable idle with out closed loop IAC then it will be worse with the valve working.

If you tune the idle as I laid out in my post you will achieve a stable idle.

I would also try setting lag factors to around 50.

David

EDIT: turn off idle advance and acceleration enrichment before tuning the idle

[asumsatlil]

this is best i got it to idle at the moment, the car drives fine and doesn't stall when coming to a stop, or pushing the clutch in at higher rpms. i adjusted everything even more than it was yesterday night, i changed the lag factors a bit and the helped out quite a bit. should i change the idle advance when below to something lower than 1300? since i have it idling at 950-1000 rpm

[asumsatlil]

i been reading the board assembly again for a mega squirt 2 v3.57 and it seems like a stepper motor would be easier than a pwm. since i only would have to add jumpers and for a pwm i'd have to solder in a new circuit
(1A)JS0 (under the processor socket) to IAC1A (near the DB37 connector) - this goes to Coil 1, lead A on DB37 pin 25
(1B)JS1 (under the processor socket) to IAC1B (near the DB37 connector) - this goes to Coil 1, lead B on DB37 pin 27
(2A)JS2 (under the processor socket) to IAC2A (near the DB37 connector) - this goes to Coil 2, lead A on DB37 pin 29
(2B)JS3 (under the processor socket) to IAC2B (near the DB37 connector) - this goes to Coil 2, lead B on DB37 pin 31
Install a jumper from the hole marked S12C to the hole marked JS9 (+12C)

[Matt Cramer]

The stepper IACs do take a bit more dialing in compared to PWM, though. With PWM, you just need to set the frequency; there are a number of step parameters to set with the stepper.

[keithmac]

I used the stock idle valve on my mk2 16v on my MS1 intstall, it was a bit of a mission to get it dialed in (ended up writing my own code in the end).

Without the idle bypass valve it was a pain during warmup, especially in winter so well worth the effort to fit one.

Quite a few cars have a microswitch to set idle mode, maybe use one to pull the tps signal to ground at idle as this would negate your tps signal issue?.

[turbo conversion]

Your last log looks much better.

Where do you have the tps grounded and is it isolated from any noise source?

Did you check battery voltage at battery vs MS (still reading low) to see if they match?

David

[asumsatlil]

The stepper IACs do take a bit more dialing in compared to PWM, though. With PWM, you just need to set the frequency; there are a number of step parameters to set with the stepper.

megasquirt. i'm not too sure what to do because i have no more heat sink space on the motherboard for the new circuit.

I used the stock idle valve on my mk2 16v on my MS1 install, it was a bit of a mission to get it dialed in (ended up writing my own code in the end).
without the idle bypass valve it was a pain during warmup, especially in winter so well worth the effort to fit one.
Quite a few cars have a microswitch to set idle mode, maybe use one to pull the tps signal to ground at idle as this would negate your tps signal issue?.

so it just would make the signal clearer? i'm not really familiar with micro switches.

Your last log looks much better.
Where do you have the tps grounded and is it isolated from any noise source?
Did you check battery voltage at battery vs MS (still reading low) to see if they match?
David

i have the tps grounded at the megasquirt, i used a shielded twisted pair to try and stop the noise, it was way worse before. i haven't checked the voltage at the mega squirt in a while. i'm thinking of buying a 10 foot ms harness to see if that will clear all my signals up. plus it would make everything look cleaner than it is now.