Block heater issue (rough startup)

[Denalibro76]

Evening everyone, I live in Central Canada so it’s damn cold a lot of the winter so plugging the block heater in is a must. I’ve discovered that when I plug it in, my Yukon really starts like crap. Turns over good but stalls 2 or three times and idles rough for 30 seconds or so. If it don’t plug it in it starts and idles fine (other than hard cranking). Might sound silly but the ECM isn’t reading the water temp for startup and not the ambient air temp is it?

 

[Foggy]

Your ecm uses water temp to determine lots of conditions including
how it's going to start up. You may want to check your Coolant Temp
on a scanner BEFORE you start it to see what the ecm is seeing.
Between water temp and water temp is how your cold starts are determined
as it's still in Open Loop - which relies on a pre program vs using all the
sensor inputs until it warms up a bit.
You probably would have to make some adjustments to "cold start" thru
HPTuners or similar to get it to start acceptably .. Then maybe have to change it
for summer parameters too

Make sure you put your vehicle info in your signature so we know exactly
which SUV you are working on / aking about for better specific advise

 

[SpareParts]

It could be there is too large of a temperature discrepancy between the water temp and the IAT that is messing with the ECU.

 

[j91z28d1]

It could be there is too large of a temperature discrepancy between the water temp and the IAT that is messing with the ECU.

there's a fault code for this some where in this site. but yeah, mainly I thought it was aftermarket block heaters that caused the issue. the factory one has a thermostat or something to avoid it.

miss match in iat to coolent temp I think you're right.

 

[Denalibro76]

Your ecm uses water temp to determine lots of conditions including
how it's going to start up. You may want to check your Coolant Temp
on a scanner BEFORE you start it to see what the ecm is seeing.
Between water temp and water temp is how your cold starts are determined
as it's still in Open Loop - which relies on a pre program vs using all the
sensor inputs until it warms up a bit.
You probably would have to make some adjustments to "cold start" thru
HPTuners or similar to get it to start acceptably .. Then maybe have to change it
for summer parameters too

Make sure you put your vehicle info in your signature so we know exactly
which SUV you are working on / aking about for better specific advise

It’s a 2009 Yukon Denali. (L9H)

 

[j91z28d1]

might search P0116 and P0115

 

[Doubeleive]

supposedly if you use autostart it ignores the ambient versus actual, at least on the t2's, not sure on the gmt900's