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!

[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.

[morrislee]

GM should waive that deductible, IMO.

 

IMO, this would be like the 5th or the 6th trip to the dealership over the span of 6 months. I'd cover the cost to replace that injector if they are saying it is not the problem anyway.

[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.

[morrislee]

None was listed on my paper work, maybe none exists but a standard procedure is in place for P050D

[Jsdirt]

I wouldn't offer up ANY of your hard-earned money. GM should've built the damn thing right, and checked EVERYTHING out before it even left the factory.

 

This is inexcusable.

[tainoxl]

I'll give them the benefit of the doubt for now and assume they are going through a trouble shoot procedure. If the code returns I will expect them to go more in depth.

[morrislee]

Well that didn't take long, truck is back at dealership code came back today. Hopefully they can fix it this time.

 

These two links should help them....

 

http://www.performancetrucks.net/forums/gmt-k2xx-trucks-general-discussion-221/p050d-code-533167/page2/#post5287545

http://www.gm-trucks.com/forums/topic/185929-rpm-fluctuation-at-cold/?p=1793458

[morrislee]

I wouldn't offer up ANY of your hard-earned money. GM should've built the damn thing right, and checked EVERYTHING out before it even left the factory.

 

This is inexcusable.

 

Yeah, but I did pass the 60,000KM base warranty, I got the GMPP right before then too when the problem started, but I did not purchase the GMPP at the time of vehicle purchase or it would have been $0 deductible.

 

Warranty will be decided at the time when the repair was performed, even say they have diagnosed the problem at 59,999KM and I decided to take it off the dealership while the parts getting order because it is still drivable, then I'd be hit with the final repair cost. at least that is what I have been getting as a response every time when I talk to them.

 

I am just unlucky that the dealership I have dealt with could not detect the problem correctly first hand otherwise I would have saved so much on gas and time to the dealership. I'd rather put some cash down that I know this is the issue and get this problem solved so no more dumping money in the pit.

[tainoxl]

I went over it with the service manager, we spoke with the tech and they are going to go that route next.

[morrislee]

To be honest, if they'd offer unlimited mileage warranty, I'd probably by that on the get-go, never had many expansive purchases in my life time that works solid problem free.

[Jsdirt]

Hard to find anything of quality these days, unfortunately.

[tainoxl]

Well based off what I just read on the service detail, they checked the harness connectors and computer. So I guess it will be going right back in the next few days when the code comes back. They pulled two codes, p050D and p0300. So there is def something going on. Like you it seems to mostly be happening on cool days during a cold start.

[morrislee]

2 12668649 injectors

1 12618336 pipe

1 12618337 pipe

1 12672366 injector seal kit

8 12626354 intake seals

None are covered under powertrain, only 3/36

 

Seems like they are trying to recreate the code, but they are unable to so they are letting the truck to cool down. Did you had to do that? Or did you went straight for testing the injectors?

[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.

[GMCustomerService]

Hello Morrislee,

 

 

I'm sorry to hear your GMC Sierra is experiencing a rough cold start concern. If you need additional assistance, please send us a private message.

 

Kind regards,

 

Anthony J.

 

GM Customer Care