Random Misfire PO300- Wisemen Needed!

[fourgsixthree33]

Mod list is up to date.

Recent history:

About a month ago, I installed a 14B. Up until the last few days, thing pulled like a champ.

Cleaned FMIC.

Problem:

After the 14B install, it would take off like a mofo. But, I was getting what I thought was fuel cut around 15-16psi. It would get to 15-16psi, pop/misfire/RPM's fall. Other times I could hit 20psi with no problems. This misfire thing happens at the top of boost/in high boost. Which is why I assumed this was fuel cut.

Now, this has been happening at 12psi and it sometimes will only boost to 10psi. The car is slow as hell now. Just ran great last weekend at the track. Now it takes forever to get into boost and it is slow when it does start to boost.

Also in the last few days, if I go just above 3500RPM's and let off the throttle, the car will misfire/buck. Pretty badly.

I have the Pot Mod, the misfire while cruising thing will occur WITH THE POT TURNED ON. With the Pot turned off, no misfire. Just the misfire that I am speaking about.

Hooked up a code reader to it today and it shows the PO300 random misfire code.

1G CAS needs to be adjusted all the way forward or else the car will not be driveable. It is terrible. It has been like this since rebuilding the engine. Mechanical timing is perfect. It has always been perfect and today I redid the timing belt due to the engine mount bracket snapping the studs. So timing belt came off.

I am not sure if a boost leak could cause this PO300 code, I have a boost leak tester but need to go to the gas station to do the BLT.

I really need some help guys. This is really bugging me. I know PieEyedPiper will chime in as I seen he always posted on threads like this. Found that out doing my search.

 

[oneslowwdsm]

There's no point in even posting anything until you have done a boost leak test. My guess is you popped/cracked a coupler somewhere and don't see it. I would check all the wiring going to your CAS as well, it should run fine advancing it either way or could just be the cas itself is bad. Check for spark at the coilpack and make sure it is strong, if it's weak, you know it's the CAS but I've never seen a CAS go bad. Also try swapping the coil pack and PTU (Power Transistor Unit) with known working ones.

 

[fourgsixthree33]

There's no point in even posting anything until you have done a boost leak test. My guess is you popped/cracked a coupler somewhere and don't see it. I would check all the wiring going to your CAS as well, it should run fine advancing it either way or could just be the cas itself is bad. Check for spark at the coilpack and make sure it is strong, if it's weak, you know it's the CAS but I've never seen a CAS go bad. Also try swapping the coil pack and PTU (Power Transistor Unit) with known working ones.

Followed this tech article to do the wiring for the 1G CAS http://magnusmotorsports.com/wp-content/uploads/2010/02/1gina2g.pdf .

I have tried multiple CAS's. Same thing. My last 1G had to have the CAS all the way forward too. But the mechanical timing was never right either.

I will try what you have suggested.