2012 Equinox 2.4L Rough Idle in Reverse

[twenzel]

Hello,

2012 Chevy Equinox with 80,000 miles on chassis and 5,000 on rebuilt engine from a reputable, national builder. Engine was replaced due to excessive oil consumption.

About 8 months after engine replacement, the 2.4 started to idle terribly when cold started and shifted into reverse.

Relevant facts:

1. Does NOT set a code
2. Does NOT set a mis-fire
3. LT Fuel Trim at -3 after running
4. ST Fuel Trim oscillates between -5 to +2
   1. Seldomly to Plus side
   2. Does seem to be quite active and all over the board
5. Throttle Position responsive and in spec
6. Cylinder Balance in spec
7. Injector pulse in spec
8. Engine Mounts good
9. Battery replaced
10. MAF sensor replaced
11. Traced each connection wire status through the loom
12. Checked pins of each connector
13. Vacuum leak checks down to the intake manifold with NO vacuum leak
14. Nothing from the Fuel Trim indicates a rich condition
15. Ran system without EVAP to test for symptom - with EVAP blocked off, symptom persisted
16. Tests and system monitor through Snap On Solus Scan Tool
17. Replaced O2 Sensor
18. .
19. When removing the Air Box, noticed what appeared to be excessive blow-by liquid remnants as the air box was removed. High Pressure fuel pump could be internally leaking causing excessive buildup in the crankcase and pushed into air box

New Parts installed during Engine replacement

1. Plugs
2. Cam Phasers
3. VVT sensor
4. Coolant Sensor
5. Thermostat

I have never seen an ECM replacement solve a situation like this, but we are at wits end here....

General Thoughts on Progression:

1. Potentially replace High Pressure Fuel Pump
2. Could swap out Cam solenoids; but they are active and within spec
3. Potentially replace ECM
4. Thought about a torque converter issue, but if the engine is not running correctly, the tranny will not function properly....and vice versa

At this point, we are leaning towards replacement of the High Pressure Fuel Pump. Any thoughts? Running out of money and patience

Condition seems to go away after the vehicle has warmed up.

Thanks in advance

 

[Tico007]

19. The buildup of moisture/liquid in the air box and in the fresh air PCV tube is a clue that the internal PCV orifice is likely blocked. Hot blow by is reversing direction and pushing out the fresh air tube meeting fresh cool air coming in. That’s how the moisture is created. It’s basically raining. It’s a common problem with the 2.4. Likely the problem with the former engine also.

The internal PCV orifice design worked until GM changed to direct injection. Now without the wash of fuel vapors near the intake ports the PCV orifice hole blocks with carbon from blow by. Another clue would be check for a lot of pressure coming out the oil filler cap at idle. When the PCV orifice blocks, it causes pretty much all the problems with the engine, including oil consumption, timing issues, vacuum/fuel related issues from the pressure created. You can also have problems with the secondary air system if you have one because of the moisture, that will show itself with a rough idle the first 15–20 seconds. The pressure can also blow the rear main seal.

There are options to less than the impact of blockage. You can drill an external hole through the intake manifold as a way to maintain the internal orifice. Or you can do what GM decided to do in the most recent engine designs. Go back to a traditional PCV valve. It can be done. It’s what I do. I’ve tested an orifice bypass on several 2.4. No issues. It’s pretty basic actually and doesn’t cost much to do. The traditional PCV valve keeps blow by headed in the correct direction. Cold air coming in one side. Hot blow by exiting through the other side. This helps with the moisture problem. With less blow by the oil stays cleaner, oil is less likely to plug the the VVT solenoids, and so on.