RPM fluctuation at cold

[morrislee]

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!

[Jsdirt]

I had to search the net for that one - never heard of a code ending with a letter ... but it seems this is a thing now.

 

Just from what I've seen on Google, everyone that has this code has a CAI & other mods, and/or ran E85. One guy said GM threw a new set of injectors in, and that fixed it. Another possible cause is carbon buildup on the intake valves due to the new DI.

[Doug_Scott]

How many miles on the truck? It would appear that you should still be under bumper to bumper warranty time wise, but may be out miles wise. If you are still under the 3 year warranty, let the dealer fix it.

 

I read on one site that GM is running the 5.3 engine with Active Fuel Management on 4 cylinders when idling. That has to create a different sounding and running engine compared to the non Active Fuel Management engines on the 2014 and newer trucks.

[morrislee]

I had to search the net for that one - never heard of a code ending with a letter ... but it seems this is a thing now.

 

Just from what I've seen on Google, everyone that has this code has a CAI & other mods, and/or ran E85. One guy said GM threw a new set of injectors in, and that fixed it. Another possible cause is carbon buildup on the intake valves due to the new DI.

 

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.

 

How many miles on the truck? It would appear that you should still be under bumper to bumper warranty time wise, but may be out miles wise. If you are still under the 3 year warranty, let the dealer fix it.

 

I read on one site that GM is running the 5.3 engine with Active Fuel Management on 4 cylinders when idling. That has to create a different sounding and running engine compared to the non Active Fuel Management engines on the 2014 and newer trucks.

 

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

[SouthernSilveradoGuy85]

How many miles on the truck? It would appear that you should still be under bumper to bumper warranty time wise, but may be out miles wise. If you are still under the 3 year warranty, let the dealer fix it.

 

I read on one site that GM is running the 5.3 engine with Active Fuel Management on 4 cylinders when idling. That has to create a different sounding and running engine compared to the non Active Fuel Management engines on the 2014 and newer trucks.

 

The 5.3 in my '14 with almost 24,000 miles doesn't do anything like that in 4 cylinder mode. It still runs smooth no matter the temp and switching back and forth is also still smooth. Before I had the exhaust done the only way I knew it was even in V4 mode was by looking at the dash. I don't think his problem has anything to do with AFM.

[Jsdirt]

Same with my '07 - switching was always seamless. I could tell when it switched, but nobody else could.

[Doug_Scott]

 

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.

[Jsdirt]

Nope - mine's too old.

[morrislee]

Update on this, picked up large amount of misfire on cylinder 7 with a bluetooth ODB2 adapter I have got. Seems to only happen when it is colder outside, hopefully it is the same issue like the other guy with P050D has where he also picked up misfires and replacing the injector fixed the issues.

 

will be making a few phone calls tomorrow and see about getting them fixed up.

[tbarn]

Just fixed a customer silverado with a P050d last week. replaced two injectors.

[tbarn]

During a cold start, the engine control module (ECM) commands dual-pulse mode during Open Loop operation to improve cold start emissions. In dual-pulse mode, the fuel injectors are energized twice during each injection event. As with misfire diagnosis, in dual-pulse mode the ECM monitors the crankshaft position sensor and the camshaft position sensor to calculate crankshaft rotation speed. In normal operation, optimum fuel delivery during dual-pulse mode produces a steady crankshaft rotation speed. If the variations exceed a calibrated value, the code will be set.

 

Note: Circuit/System Testing requires cold start. Do not start vehicle prior to connecting scan tool and preparing to evaluate the condition during engine crank.

 1. Start the engine and observe the Cylinder 1–8 Current Misfire Counters during the first 500 engine cycles. The Cylinder 1–8 Current Misfire Counters should not be incrementing.
⇒ If the misfire counters are incrementing on one or more cylinders
1.1. Ignition OFF.
1.2. Verify that the following conditions do not exist:
◦Fuel pressure that is too low or too high — Refer to Fuel System Diagnosis.
◦Contaminated fuel — Refer to Alcohol/Contaminants-in-Fuel Diagnosis.
⇒ If a condition exist, repair as necessary.
⇒ If none of the conditions exist, replace the Q17 Fuel Injector(s) as indicated by high misfire counts.

[Jsdirt]

Interesting. Thanks for the info.

[morrislee]

Just fixed a customer silverado with a P050d last week. replaced two injectors.

How many hours did it come to for the work? Do dealership usually have these injectors instock?

[tbarn]

Had to order parts. Seems like it was 2-3 hours + diag. Not sure though. If anyone but a dealer does this repair, you need to replace the fuel lines that are removed. They are one use only. Dealer should know this. Others may not.

[morrislee]

Had to order parts. Seems like it was 2-3 hours + diag. Not sure though. If anyone but a dealer does this repair, you need to replace the fuel lines that are removed. They are one use only. Dealer should know this. Others may not.

Could you please list the part numbers replaced? I want to make sure if they did the same procedure, the fuel line you are referring to is also covered. How long did it take to order? If my injector is bad, do the dealership put the truck back together until the part arrives or am I going to have to leave it disassembled there until part arrives?