RPM fluctuation at cold

morrislee · April 8, 2016

On cruise, I have a slight RPM fluctuation at start of a colder day, I have been getting he code P050D for Rough Cold Start (which is bad enough that I can notice when the code will trigger)

What could be the problem?

Truck is Sierra 1500 2014 with 5.3L ecotec3

If it is injector, what test can I run to narrow it down without taking off the intake manifold?

If it is the sparkplugs, how do I test them?

Please assist, thanks!

Doug_Scott · April 10, 2016

Pretty sure it is related to my other problem where the RPM fluctuate on highway and eventually the TCC opens for more slipping to allow more fuel flow on cruise. dealer could not reproduce the RPM fluctuation issue and unable to do anything. sick of wasting time on them.

passed the 60,000km warranty (Canada) and V4 is disabled. My other code was P219A and both of these codes has been fixed by a street tuner right now, but the RPM fluctuation is probably related to P050D and I was wondering if anyone has any thoughts on the code.

BTW, truck should not normally be idling at V4 especially when it is cold. If yours is doing it, I think it has to do with this recall http://www.autonews.com/article/20140110/RETAIL05/140119956/gm-recalls-303000-new-chevy-silverado-gmc-sierra-pickups-for-engine

I don't have Active Fuel Management on my truck, it has the 4.8 engine. The site I found mentioned that they are running the engine in v4 mode when idling. The recall you mention likely corrects an error in the firmware that still injects fuel into the now deactivated cylinders causing the catalytic convertor to overheat, creating the fire hazard.

I know this is off topic, but did anyone else get a letter last week saying there may be an issue with the rear leaf spring pack on the 2010 model year Chev/GMC 1500 trucks, and that GM will fix it for free if you are still under the 5 year, 160,000km warranty? Don't know how many of the now 6 year old 2010 model year trucks are still under the 5 year warranty though.