Diagnostic Detective Work Needed - Running Lean

[austtie]

Hello Friends,

I've been having an ongoing issue with my 2014 Sonic that after several appointments, my mechanic gave up on trying to fix. And it has only been getting more confusing.

It all started with a P0299 code. Turbocharger Underboost Condition. The only change I noticed was a possible decline in gas milage.

My mechanic tried to tune the turbo by tightening the arm connected to the wastegate. For context, I have an aftermarket turbo that he replaced after the stock one failed at about 110k. I'm now at 150k. A day or so after replacing the Turbo, my sonic threw a P0299 that he fixed via tightening that same arm.

40k miles later, the code was back and nothing would fix it.

Then the P0234 code threw. Turbo Overboost Condition.

He replaced the mass airflow sensor. The issue persisted. He said the only possibility left was a bad Turbo.

Well I've been driving my Sonic and only recently has it started to lose power. So I began my own research. It's now throwing both previous codes (off and on) and P2227, P015B, and P1101.

For further context, at about 130k miles, my car threw P0420 and I tried to wash the Cat. Nothing stopped this code and I lived in CA at the time - so a new Cat was off the table. I installed a spacer on the downstream 02 sensor. No issues after that.

Here are readings I'm getting as of today. Any guidance is very welcomed.

 

[Simplyjesse]

Well a negative long term fuel trim means either less air or more fuel is present during combustion then intended. The ECU is trying to pull fuel out because the O2 sensor is detecting a rich mixture, this is calculated using the map, maf, and O2 sensor. The under boost/over boost situation is exactly what it sounds like as determined by the map sensor and or the mass air flow sensor. If I had to guess I would say it could be several things. Bad map sensor, obstructed cat, obstructed air filter, or vacuum leak. Diagnose vacuum system with smoke machine, replace map is a good starting point.

Also this forum is dead, try cruzetalk.com if you have problems in the future. They're the same cars and there is still some life on that forum. I just happened to be researching something and stumbled on your post. Cheers and good luck.....