2016 Chevrolet Impala 2.5 intermittent sralling

John Owner/Technician Prospect Park, Pennsylvania Posted   Latest  
Discussion
Driveability
2016 Chevrolet Impala LS 2.5L (A LCV Flex) 6-spd (6T45)
P0506 - Idle Control System RPM - Lower Than Expected

We initially had a intermittent stalling High pressure pump was below spec so we replaced. All seemed well drove over 100 miles gave back. Car came back same problem. Smoked it no leaks, re- torqued all manifold bolts as per TSB same issue. We can run in open loop car will run fine, put in close loop falls on its face and stalls. Any suggestions as to what direction. Has auto shutoff and it seemed to happen here more than any other time.

0
Nelson Diagnostician
Gastonia, North Carolina
Nelson Default
 

How does O2 sensor activity look? Proper switching, etc? Fuel trims OK?

0 Default Ð Bounty Awarded
John Owner/Technician
Prospect Park, Pennsylvania
John Default
 

O2s in spec actually set monitors for Emissions, Fuel trims we’re also in line , re cleaned throttle body, did an idle re learn. We backed up and went through everything again not sure what we’re missing. Don’t want to condemn throttle body.

-1 Default Ð Bounty Awarded
Joel Diagnostician
Soquel, California
Joel Default
 

Why it goes in open loop?? Idle , 2500 rpm and under load? Any fuel control issues , what is total fuel trim per bank ??

0 Default Ð Bounty Awarded
Todd Diagnostician
Macomb, Michigan
Todd Default
 

What is the low side fuel pressure when the issue occurs? I had one a couple of years ago that had a loose ground terminal at the fuel pump connector and would slow the pump down enough to drop the low side fuel pressure intermittently. You should be able to see the low side fuel pressure PID on the scan tool. The other thing I've seen on the 2.5L is malfunctioning VVT solenoid(s). Again, you…

0 Default Ð Bounty Awarded
Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
   

How is the oil level and conditon? Whats the miles? And it looks like Todd beat me too it. The 2.5 VVT solenoids are notorious for causing hot idle random stalls. Unplug them an drive it and see of the problem is gone.

0 Default Ð Bounty Awarded
Brian Technician
Spring City, Pennsylvania
Brian Default
 

Sounds like a classic GM throttle body issue, some of them had connector issues where the pins get loose and harness issues, plus the plastic cover to the electronics used to get moisture inside because the rubber seals stink and let moisture in, give the connector a good wiggle test while running, see if thats make it stall or run funny.

0 Default Ð Bounty Awarded
Albin Diagnostician
Leavenworth, Washington
Albin Default
 

Since it will not run when it goes to closed loop, why? Are you aware of the enabling conditions for closed loop? When it goes closed loop, does it run lean, or flood its self out with fuel? Do you have access to an exhaust gas analyzer? If not, you can get a lot of information from the trims & the oxygen sensors. Capture some trim and oxygen sensor information graphs, then put them up…

+1 Default Ð Bounty Awarded
Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

Im sorry I see that it stalls in closed loop. Not sure how I missed that. The Malibu an Impala 2.5s of this era also have 02 Sensors that fail to respond fast enough when it goes into closed loop. Have a good look at 02 data when it goes in to closed loop. I bet one sensor is not responding.

0 Default Ð Bounty Awarded
Caleb Diagnostician
Mishawaka, Indiana
Caleb Default
 

Did you figure this car out??

+1 Default Ð Bounty Awarded