Acceleration issues and flashing Check Engine Light?

Hello, if your Catalytic Converter got that hot, it melted down, did you check the rest of the exhaust for sections of the Converter. When they melt down and block off the exhaust chunks will go into the rest of the exhaust. It sounds like it's still blocked up, or the vehicle is going into limp mode and restricting acceleration. The flashing check engine light indicates a Catalytic Converter damaging misfire, although you've already removed it, the ECM is still seeing a misfire bad enough and it does not know you have removed the Converter. It may still be in Limp mode due to that misfire issue, and the ECM is still trying to protect the Converter. You replaced the coils and plugs, but with the exhaust getting that hot, it may have burned an exhaust valve. Try doing a compression test on that cylinder, unplug the fuel injector while doing it so you don't get any cylinder wash happening.

https://www.2carpros.com/articles/how-to-test-engine-compression

Okay, there's no reason you should have to shift an automatic transmission like that, that's not good for the transmission. And the idea that it needs to sit and warm up before you can drive tells me that it's most likely the air/fuel mixture is off in one direction or the other. A cold engine requires a lot more fuel to run with its normal output than a warm engine to begin with. Is the check engine light on and is there any other codes now besides the misfire code? Any oxygen sensor codes or rich/lean codes? With the Converters being gone now, the rear oxygen sensor is going to report skewed readings to the ECM. Do you have a scan tool that can read live data? I think taking a look at the Long Term and Short-Term fuel trims will give you a better idea of how much the If you have any questions is compensating with the fuel system.

As for the exhaust, the static compression numbers actually look a little high, 128psi is the min. So, there might still be a restricted exhaust. The muffler is where pieces of the converter would get caught in, the muffler has baffles in it to reduce sound, and that's where all the broken chunks would go. So, check that, probably unbolt it and be sure it's not blocked up.

If that's not the issue, then it's most likely going to be the computer leaning the exhaust out. It will compare the oxygen sensors (front and rear) to keep the air/fuel mixture within emissions standards. These systems will learn what the best air/fuel mixture is after a while to prevent excess emissions, but it's hard to tell what's going to happen when the converter is removed. It usually takes a tune kit to the If you have any questions to disregard what its programmed to do. Without the converter it's going to see all those emissions gases that are not supposed to be there and mess with the mixture. That may be why it won't have any power until it warms up. It may learn to compensate somewhat, but the system has been modified now. Looking at the live data is the only way to know what the computer is actually doing. But start with checking the rest of the exhaust for restrictions.

https://www.2carpros.com/articles/how-emission-control-systems-work