Starts but stumbles and dies without throttle.

[gtmdriver]

Air cooled VW 1600cc engine with MS2 V3 Firmware 3.4.2.

I'm really pleased with the tune I've achieved so far using VEAL. The car is already running much better than it did on the twin carbs and idles steadily once it's fired up.

Only a minor problem really but one which I'd like to sort out if possible.

I have a 4 wire stepper motor IAC valve. The GM Jeep one sold by DIY Autotune.

If I rely solely on the IAC valve when starting the engine it will fire up easily, idle slowly for a couple of seconds then stumble and die.

If I use a whiff of throttle when starting the engine it fires up easily then continues to run on the open throttle for a few seconds after which it will settle down to a steady fast idle which reduces as the engine warms up finally idling steadily at 850 rpm when warm.

I have tried various settings for the ASE, the ASE taper and the WUE but I haven't managed to cure the problem or even go some way to improving it.

As I said it's only a small niggle and the workaround is easy but I'd like it sorted if possible.

If you could look at my tune and/or my log to see what I've done wrong I'd be very grateful.

John

[turbo conversion]

I would start with lowering cranking rpm to 300 instead of 600.

Then you need to add more after start enrichment until it stays running.

David

[turbo conversion]

I have a question about your Primary Fuel and Primary Ignition load settings.

Primary Fuel Load is set to Alpha-N and Primary Ignition Load is set to Speed Density, I have never seen this before.

What is the reason for this, just trying to learn something here.

David

[gtmdriver]

I would start with lowering cranking rpm to 300 instead of 600.

Then you need to add more after start enrichment until it stays running.

David

OK. I'll get straight on to that.

For future reference what effect will lowering the cranking rpm have?

Shouldn I increase just the ASE or should I also lengthen the ASE taper time too?

[gtmdriver]

I have a question about your Primary Fuel and Primary Ignition load settings.

Primary Fuel Load is set to Alpha-N and Primary Ignition Load is set to Speed Density, I have never seen this before.

What is the reason for this, just trying to learn something here.

David

I can explain that!

I'm an idiot!

I tried so hard to read about and understand the various functions as I was filling them in and I completely missed that one.

Thanks for pointing that out in such a subtle way.

They are now both Alpha-N.

[turbo conversion]

I would start with lowering cranking rpm to 300 instead of 600.

Then you need to add more after start enrichment until it stays running.

David

OK. I'll get straight on to that.

For future reference what effect will lowering the cranking rpm have?

Shouldn I increase just the ASE or should I also lengthen the ASE taper time too?

You want the cranking rpm about 150 rpm above what the starer is spinning the engine when cranking.

Notice in your data log after the engine fires when the rpm falls below 600 it goes back into cranking mode and engine dies.

If it is set to 300 rpm it will have to fall below that before it goes back into cranking mode.

At 300 rpm MS will go into run mode instead having to achieve 600 rpm.

I would start with increasing ASE first until the engine does not die on the first cold start.

Notice in your data log once the engine fires there is a lean spike rpm goes below 600 rpm then the engine dies, this is caused by not enough ASE.

Once you get ASE correct then you can dial in the taper.

David

[gtmdriver]

Those change seem to have done the trick.

It started up and idled away quite steadily this morning. No issues with revs dropping or dying.

Thanks very much for the advice.

[turbo conversion]

Awesome, happy tuning

David

[dmiletics]

Hi John I am having similar problems with my 1977 Beetle. I am using the stock VW throttle body and plenum with a Bosch idle valve from a VW golf and ms1. It starts first try but the idle stumbles for 30 seconds then settles into a steady idle that slowes down as the air valve progressively closes.
I am guessing this means I need to tweak my after start enrichement and not my cold start enrichment.
Have you been able to get reliable cold starts yet?
What are your cranking and after start enrichment settings ?

Thanks David
Montreal Canada

[turbo conversion]

Can you start a new thread with a data log and msq?

David

[dmiletics]

Sorry will do. I hijacked this thread by mistake I thought I was joining a discussion for air cooled VW engines.

[turbo conversion]

No problem, will be looking for it.

David

[oscarmax]

I have the same problem, I will try this solution on mine to see if it works.