2G P0300 Code PCM/ECU/Something else?

[pressf1forhelp]

97 Eclipse GST with 195k miles.

So after 4 years of doing my own work on the car and enjoying everyday of it, including the ones I sat in a corner and cried ahahah, I had to take her to a shop.

Shop #1: They resealed the intake manifold and re-did a bunch of vacuum hoses to fix a idle issue that was not throwing a code for whatever reason. Fixed nothing, so they charged me nothing.

Shop #2: Just put new belts on it since the car was there but with a misfire code P0300 (random misfire). They also fixed my idle issue which was just the cruise box taking in too much throttle cable. New coil coil pack for 2 of the cylinders to try to get rid of the CEL, not sure which cylinders.

The issue: The code did not show up until Shop 1 worked on my car and that particular code I've never dealt with since owning this car. Shop 2 says that the car is mechanically sound (compression was close to perfect spec wise) and they think it's an electrical issue with the PCM telling 2 of the cylinders to shut off causing the whole car to just die. The car runs and drives fine otherwise. They said that after a few minutes of the car idling or driving boom. PCM or the ECU tells one or the other to shut off two of the cylinders via coil pack and the whole car dies and starts up fine again when the key is turned. Here's a list of what I've done over the years and what the shops did the past week or so.

Me:
Spark plugs (yes I checked the gap yes they are the NGK ones that everyone bows to) and wires
ECT
Valve cover gasket
IAC
Oil changes regularly
All of this work I did has under 1-4k mileage and probably has nothing to do with my issue, but just so none of this stuff comes up.

Shop 1: Didn't do #@#@$@ and left me with the check engine light
Shop 2: New belts excluding the timing, new coil pack to try to get the check engine light to go away, compression test

So, does the car have a PCM or am I looking at getting a new ECU or? Just shooting ideas out there. Some insight would be greatly appreciated.

 

[spyderdrifter]

PCM and ECU are the same thing depending on what that manufacturer refers to it as.

You very well could need a new one. However you want to be sure before spending the money on one and then still have the same problem. I would search for someone that has the same year car and borrow a known good ECU. If the problem continues, your ECU is fine.

That's where I would start. Also look at your ignition power transistor. That thing powers your coils. If it's bad, your coils won't work, leaving you with no spark.

 

[pressf1forhelp]

Also look at your ignition power transistor. That thing powers your coils. If it's bad, your coils won't work, leaving you with no spark.

Thanks. Will check once the sun is out. Isn't PT/Coil pack a separate CEL code though? I guess if both PTs were bad the ECU would throw a random misfire code instead. I'll let you know in a bit.

 

[spyderdrifter]

There's only 1 power transistor powering both coils. I don't recall a code specific to the power transistor, but could be wrong. Also make sure the transistor is fully plugged in. The orange weather seal on the inside likes to swell and cause the plug to loosen up... I know from it happening too many times. Ended up cutting the seal down and then zip-tying the connector on.