stalls when i turn my headlights on

[Mx73]

sometimes it'll stall when i put my headlights on, it usually happens during warm up

[trakkies]

What is the idle speed when this happens? And the air/fuel ratio?

[Matt Cramer]

This may be a case of the battery voltage compensation being off. Could you post a data log of this happening and a copy of your MSQ?

[Mx73]

when battery says 12.7v megatune says 13.1-13.3 and keeps bouncing, at 14.2v battery megatune reads 14.9v


i didn't get it to stall out this time. but idle kept flucuating when i turned all accessories on.

[Mx73]

heres the log

[trakkies]

What's the correct idle speed for your engine? It appears to be circa 600 rpm which is pretty low these days. And if the idle tune isn't spot on any extra load could cause it to stall. When warming up, even more so.

[Mx73]

when i have it idle higher it still is pretty hard to get started, gotta hold it 5 seconds or more, and i gotta tap the throttle a little, sometimes it'll just fire then die and i'll have to crank it a few more times ,shuts off if i turn lights on, or heater/brake lights. unless i hold the rpms up higher and let it warm up.,, but how would i adjust voltage correction in ms, , shouldn't it run normal at 12.6volts anyway?., 12-14.7, i think it's while the battery voltage slowly rises to 14+ , , thanks for anyhelp

[Matt Cramer]

Try setting it to idle a little bit richer than 14.7:1 - this often gets a better idle. And try increasing the idle speed with the IAC valve instead of adjusting the throttle plate.

[flatbill]

My '56 Desoto motor is happiest at about 13.5 AFR at idle. Billk

[trakkies]

My '56 Desoto motor is happiest at about 13.5 AFR at idle. Billk

Sounds about right for a car originally on carbs. Mine had factory injection (Lucas) with no cat. and the spec for that was 14.1. So I've kept that with MS. But it will idle reliably much richer.

[flatbill]

Per the megamanual, I adjusted the VE table until I got the lowest MAP reading at idle. Was easy and worked well. You just need to find what the motor likes best. Billk

[trakkies]

Per the megamanual, I adjusted the VE table until I got the lowest MAP reading at idle. Was easy and worked well. You just need to find what the motor likes best. Billk

In the UK they check the idle emissions (according to age) at MOT time, so I thought it safer to stick to the factory spec. With a '56, they'd just check for visible smoke. ;-)

[Mx73]

still having some issues. got a 130amp alt vs 65amp stock, all new ground wires, it takes a while to start up when cold, maybe too much fuel, or no spark, it will misfire on startup , i have a good battery, and alt,, afr will go down to 9-10 when cranking, have to tap the gas for it to fire, but only after cranking for like 5seconds, , its a fresh motor, compression is great, had this issue before/after i rebuilt it, could it be just because im not running a IAC, im stil not sure why it would missfire and if i touch the gas too hard it just stalls, i have to tap it to get going when gits cold,

[flatbill]

The starting problem might be the lack of the IAC. On my Megasquirt, I set the cranking IAC position. After it starts it runs with a startup IAC position for a set (short) length of time, then it goes to the IAC coolant temp table to reposition the IAC. With this setup its a "no foot on the gas" startup. Billk

[Mx73]

i think whats happening, there is fuel and its running rich, but since its a o2 sensor, telling me im 9-10:1 as it goes from 22 down to 9 when cranking, it's gotta be just the lack of oxygen, , even after start up, it hovers around 11:1 , after aw hile goes to the 14's, ,

i have a iac i can put on, but i dont think it has a check valve for boost, should i just run it straight to my pipe in front of my Throt body, ,