2011 Chevy Silverado 1500 Rough Start

[rooz240]

I am having the same issue as bassmaster with my 2011 truck. When the engine is cold I have a rough starting truck just like his video. Has anyone figured out for sure what the fix is? Bassmaster did you ever get this fixed? thanks.

[rooz240]

Hello All,

 

I’m sorry to hear that you all are experiencing this problem with your vehicles. I would like to look further into your concerns. If I can be of any assistance, please private message me your VIN so that I can take a better look at your vehicles. Thank you.

 

Kristen A.

GM Customer Care

1GCRCREA6BZ242746 is my vin number. I started having this problem last week. so far the repair shop has changed the fuel pump and the throttle body and I still have the same problem. thank you.

[rooz240]

Have your dealer or someone with a decent scan tool check to see what ethanol content your computer is reading. Depending on what fuel you're using (not E85) you should see 10% or less. My 2010 5.3L was having exact same symptoms. Computer was seeing 58%. PCM is SUPPOSED to calculate ethanol content from info received from O2 sensors, fuel level indicator and vehicle speed sensor. We all know computers do things for no reason. Dealer tech did not know for sure what happened, all sensor outputs were good. A reprogram of PCM put reading back to normal (3%) and all is well.

Since this fix, has your problem stayed away? My 4.8 just started having this problem and I am struggling with it now. My truck has 147000 miles on it. Thanks.

[Gone Again]

rooz240

My truck has been perfect since this repair. No more issues.

Good luck

[rooz240]

Well my truck seems to be fixed too. A reflash of the PCM and the problem went away since I picked it up from the shop yesterday. I will have to see if it stays away. I will update later.

[WilliamBos]

My 11 has been flawless. Hope this reflash has been done already

[bgbdwlf2500]

I know this is an old post but was having the same issue so thought I would post my experience. It happened to me after going from e85 back to 87 octane and changing my superchips tune from the 91 octane to the 87 octane tune. since they say 7 mile after the fuel switch I did it right before I drove 180 miles. truck ran normal all the way there but noticed the start-falter after it sat and cooled down. chalked it up to a fluke but it did it again. so basically the same issue everyone else that has posted here has, falter on cold start, starts normal when warm, runs fine when running. This morning it actually took cranking on it to get it to start and it did and ran fine after it started. I decided to fill it back up with e85 just to see if it would help. started it up after about 5 hours of sitting and it cranked right up but it was sitting in the sun so it may have kept it warm enough. I will post back again tomorrow after the temp drops to see if going back to e85 actually helped. I also set it back to stock hoping that would help the issue. planning on reinstalling the tune when the issue is resolved. 

[carnau]

1 hour ago, bgbdwlf2500 said:

I know this is an old post but was having the same issue so thought I would post my experience. It happened to me after going from e85 back to 87 octane and changing my superchips tune from the 91 octane to the 87 octane tune. since they say 7 mile after the fuel switch I did it right before I drove 180 miles. truck ran normal all the way there but noticed the start-falter after it sat and cooled down. chalked it up to a fluke but it did it again. so basically the same issue everyone else that has posted here has, falter on cold start, starts normal when warm, runs fine when running. This morning it actually took cranking on it to get it to start and it did and ran fine after it started. I decided to fill it back up with e85 just to see if it would help. started it up after about 5 hours of sitting and it cranked right up but it was sitting in the sun so it may have kept it warm enough. I will post back again tomorrow after the temp drops to see if going back to e85 actually helped. I also set it back to stock hoping that would help the issue. planning on reinstalling the tune when the issue is resolved. 

The alcohol sensor is probably the fault. It is probably stuck at 80% or higher. A reprogram of the ECM should fix that. They can also reset it with a Tech 2 

[bgbdwlf2500]

On ‎11‎/‎10‎/‎2017 at 3:51 PM, carnau said:

The alcohol sensor is probably the fault. It is probably stuck at 80% or higher. A reprogram of the ECM should fix that. They can also reset it with a Tech 2 

Filling the tank back up with e85 has fixed the rough start issue, just curious if the next time I need to run 87 if it is still going to be stuck at the higher percentage

[carnau]

8 hours ago, bgbdwlf2500 said:

Filling the tank back up with e85 has fixed the rough start issue, just curious if the next time I need to run 87 if it is still going to be stuck at the higher percentage

It will be if it is stuck. Will need an ecm reprogram or tech 2 reset.

[DrFiero]

Hate to reply to such an old thread, but...

 

If you find that you have a hard start after it's been sitting for awhile, but not after it's been sitting for like 15 minutes - get a manual fuel pressure gauge and hook it up.  Don't use a scan tool! Turn on the key, and see what your pressure is at.  Fire it up and compare. 

 

I was having this issue for ages.  I was also getting a HUGE discrepancy between the gas pump, and what the DIC said I was using.  All my other GM's are quite accurate.

 

It's a somewhat well know problem of having 'issues' with the FPCM.  Mine was corrosion on the connector. The ECM was always seeing that I had about 43psi pressure on the rail.  So, the ECM kept commanding the FPCM to speed up (increase the duty cycle) to get the pressure up.  Of course, it couldn't read the pressure sensor right, so just kept going higher!

 

When I finally narrowed it down to this, at key on I was reading just over 90PSI at the rail!!!  Fire it up, it'd drop to about 75psi. 

Still a far cry from the ~50psi you'd expect at idle.

 

Pulled the controller, cleaned all the pins.  Hit the chassis connector with some D100. 

Back together, and the ECM was finally seeing something other than 43psi!  Yay! 

Wasted a stack on a new set of injectors during testing (thinking I had a bunch of leakers).

 

[carnau]

53 minutes ago, DrFiero said:

Hate to reply to such an old thread, but...

 

If you find that you have a hard start after it's been sitting for awhile, but not after it's been sitting for like 15 minutes - get a manual fuel pressure gauge and hook it up.  Don't use a scan tool! Turn on the key, and see what your pressure is at.  Fire it up and compare. 

 

I was having this issue for ages.  I was also getting a HUGE discrepancy between the gas pump, and what the DIC said I was using.  All my other GM's are quite accurate.

 

It's a somewhat well know problem of having 'issues' with the FPCM.  Mine was corrosion on the connector. The ECM was always seeing that I had about 43psi pressure on the rail.  So, the ECM kept commanding the FPCM to speed up (increase the duty cycle) to get the pressure up.  Of course, it couldn't read the pressure sensor right, so just kept going higher!

 

When I finally narrowed it down to this, at key on I was reading just over 90PSI at the rail!!!  Fire it up, it'd drop to about 75psi. 

Still a far cry from the ~50psi you'd expect at idle.

 

Pulled the controller, cleaned all the pins.  Hit the chassis connector with some D100. 

Back together, and the ECM was finally seeing something other than 43psi!  Yay! 

Wasted a stack on a new set of injectors during testing (thinking I had a bunch of leakers).

 

Absolutely. A manual pressure gauge is always the way I like to go. Sometimes the information you see on the computer isn't as accurate as it should be. Sometimes the computer will not see a Spike or sudden drop in pressure. Also with a manual gauge you can check and see if you're losing pressure through the check valves or in the injectors causing long starts in the morning and ect. I have a cheap ATD I have used for years. Works fine till this day and I use it all the time. http://amzn.to/2Bsm4ve