1g in 2g misfireing!

[eclipse98GST]

I just got a 1G motor swaped into my 98 GST and it runs great for the first 8 or so hours. But after about 8 hours of running it one of the cylinders starts to drop and wont fire. The motor starts to shake real bad and i can feel the cylinder not firing. I took it back to the shop to have them take a look and they replaced the coil pack and it ran fine for another 8 hours then did the same thing. If you have had any experience with this situation please let me know. Also some things that i found that it could be was one, the PCV valve may have not been open due to a restrictive tube. Or two, my air fuel guage was acting kinda funny and not cycling like it used to but i just replace the O2 sensor so i know that that cant be it.

 

[EagleTalonRacer]

Im having the same problem before and after I replaced the head gasket, but my check engine light was on before I replaced the head gasket and I got a valve job and resurface and a compression test, then after it was gone, I replaced the fuel filter still its sounds like yours, but mines a 2g. im still trying to figure out whats causing it but ill update

 

[ADrewzki]

Are you positive that the cylinder is not firing? Some swaps get the random "misfire" which causes the engine to retard timing. This will cause a huge loss in power as well as shuddering of the car. Do you get a CEL when it happens?

 

[eclipse98GST]

i do get a CEL and it reads Random Cylinder Missfire Detected.

 

[ADrewzki]

Yeah, it's probably not the fact that anything is wrong. Many swaps have this problem and one solution is to wire a 10k potientiometer (variable resistor) into the barometric pressure pin of your ECU. Few have had success with this mod. Personally, I haven't. My advice would be to save up for a dsmlink. That's the best way to go. The random misfire code is probably P030x and the engine probably runs fine once the CEL is cleared and is restarted.