I’ve had it since January and it ran rough when I bought it. I’m assuming it was sitting a while (mud dauber nests on the intake) and virtually everything is still factory.

I started with the usual suspects (plugs, coils, wires, intake gasket) and with every replacement it would run a little bit better every time but then ultimately revert back to its previous state. I changed the MAF, throttle body, and 02 sensors. Fuel pressure looks good on the scanner and fuel trims swing wildly between lean and rich.

The cats went bad so I swapped em out for long tubes and it ran great for 2 days and now I’m back to where I was in the beginning. AFM has been disabled (not deleted), I don’t have a lifter tick, and it’s generally not behaving like it’s got low compression. Anyone have any ideas?

Cliff notes: idles rough and pings, no codes. Feels choked out under acceleration. Changed MAF, O2 sensors, throttle body, plugs, wires, coils, intake gasket. Cats went bad, installed long tubes, ran great for 2 days, back to idling rough etc.

 

Welcome from Florida. Do a compression check on the engine.

 

What codes is it setting?

 

no codes besides downstream 02s for missing cats. It’s recently started to almost stall when I come to a stop. Perhaps a vacuum leak?

 

Could be the MAP sensor. I had one kill my mpg by 3 and it did not set any P codes.
Vacuum leak is a possibility also.

 

Update: recently got another code for bank 1 running lean (p0171). Also, I noticed that when viewing live data on my scanner when it starts to run worse my scanner shows rpm at 8400 and all sensor data skews as if the vehicle is actually redlining. I dunno if that’s just a scanner quirk or if the pcm is actually providing faulty information. It only happens once I’m at operating temp and I’ve reproduced it multiple times

 

Check all the grounds for the PCM and engine. There is a a lot of them, and some are shared among modules. Use a good electronic cleaner/lubricant in the connectors.
Since it does it when it gets hot, I'd suspect a bad connection somewhere due to thermal expansion.