SOLVED I am out of ideas. Down on power. No DTC

[Uluz2a6]

2015 Encore 1.4 108K

Purchased it a week ago with an overheating condition. Diagnosed it and found a cracked head, clogged PCV diaphram, failed intake, bad turbo, and multiple Amazon parts installed.

Replaced cylinder head, intake, valve cover, PCV pipe, turbo/exhaust manifold, throttle body, MAP sensor, thermostat, spark plugs, and air filter. All genuine GM parts.

Repairs were frustrating as this engine isn't fun to wrench on. Plus 105 degrees here in Las Vegas. After completed the car started and idled well. All drive monitors (except evap) cleared and it passed SMOG.

The issue it has is hard to describe, so I am hoping another tech out there has experienced it or can at least tell me how to diagnose it.

At wide open throttle it will sometimes not respond/ make power. Scan data shows WOT and TPS at 100%. If I smash the pedal the scan data goes 100%. If I "sneak up" on it slowly, sometimes it will max out at 65%. The new throttle body is GM, but the Amazon unit I replaced also acts the same. APP sensor 1 & 2 data look perfect.

All scan data looks accurate. No trouble codes. The only hint I get from ECM is an occasional stabilitrac warning light, but it is NOT present when I experience the lack of power issue.

Any ideas would be appreciated.

 

[MelsRegal]

2015 Encore 1.4 108K

Purchased it a week ago with an overheating condition. Diagnosed it and found a cracked head, clogged PCV diaphram, failed intake, bad turbo, and multiple Amazon parts installed.

Replaced cylinder head, intake, valve cover, PCV pipe, turbo/exhaust manifold, throttle body, MAP sensor, thermostat, spark plugs, and air filter. All genuine GM parts.

Repairs were frustrating as this engine isn't fun to wrench on. Plus 105 degrees here in Las Vegas. After completed the car started and idled well. All drive monitors (except evap) cleared and it passed SMOG.

The issue it has is hard to describe, so I am hoping another tech out there has experienced it or can at least tell me how to diagnose it.

At wide open throttle it will sometimes not respond/ make power. Scan data shows WOT and TPS at 100%. If I smash the pedal the scan data goes 100%. If I "sneak up" on it slowly, sometimes it will max out at 65%. The new throttle body is GM, but the Amazon unit I replaced also acts the same. APP sensor 1 & 2 data look perfect.

All scan data looks accurate. No trouble codes. The only hint I get from ECM is an occasional stabilitrac warning light, but it is NOT present when I experience the lack of power issue.

Any ideas would be appreciated.

Have you tested fuel pressure?

 

[Uluz2a6]

Scan data shows 48psi idle and around 55 PSI @WOT

 

[RD_Atlanta]

I think that I would rule out the cause being exhaust system restriction. When this does happen, its as though the power output hits a wall just as you described.

 

[Uluz2a6]

The issue has been resolved. The only sensor the last owner didn't replace with Amazon crap was the mass air sensor. I cleaned it as part of the cylinder head repair and assumed it was good because data was what I expected to see at idle. I saw it face plant during the no power issue, but so did all the other data
I was graphing. I decided to swap it with a known good from another 1.4 (Chevy Cruze) and I could almost hear theme from Star Wars play as I took out on test drive! It runs perfect! The no DTC really did point to a sensor providing bad intel, I just didn't have the ability to pinpoint which one. I have zero regret replacing all the Amazon sensors with GM units. I did that even before I knew it had the issue. Thank you all for replying to the thread as well as messaging me. Great community here!

 

[RD_Atlanta]

The issue has been resolved. The only sensor the last owner didn't replace with Amazon crap was the mass air sensor. I cleaned it as part of the cylinder head repair and assumed it was good because data was what I expected to see at idle. I saw it face plant during the no power issue, but so did all the other data
I was graphing. I decided to swap it with a known good from another 1.4 (Chevy Cruze) and I could almost hear theme from Star Wars play as I took out on test drive! It runs perfect! The no DTC really did point to a sensor providing bad intel, I just didn't have the ability to pinpoint which one. I have zero regret replacing all the Amazon sensors with GM units. I did that even before I knew it had the issue. Thank you all for replying to the thread as well as messaging me. Great community here!

Thank you for sharing, I suppose it's time to reconsider Amazon sensors.

 

[G-546680]

To be fair and clear, the actual sensor that failed was indeed a GM OEM mass air sensor. It was apparently the original unit with 10 years and 108K on it. I replaced all the Amazon sensors out of experience. They will let you down 99% of the time. Especially parts that are so highly calibrated like oxygen sensors, mass air meters, fuel injectors, etc.