Last night I installed my AEM FPR. I have a 99 Civic Si w/Greddy turbo and Walbro 255 lph high pressure fuel pump. I changed the orifice to the silver one (mid size) from the stock black, and set the fuel pressure with the vacuum line disconnected and plugged to about 45 psi. Today the check engine light comes, which turned out to be codes 72, 73, 74 for random misfire. I reset the ECU and adjusted the pressure a little higher to about 47 psi. I reset the ECU again after adjusting the pressure. Should this fix my problem or do I need to go with the largest orifice since I have the high pressure Walbro?

 

I'm using the smalles orifice and a walbro with no problems.

I'm only running 36 psi though. Try turning it down not up.

 

switch the orfice to the bigger size one and that will fix the prob garunteed, i had the same prob .
its becuase the pressure from the walbro pump .


[Modified by itr206, 5:26 PM 2/19/2003]

 

If you took it apart I will put money on it that when you put it back together you pinched the diaphram and now its cracked...It happened to me and it caused the same problem.

 

Well, I hope you're wrong! I guess I'll find out tomorrow because I'm going to put in the largest orifice like itr206 said. I was really careful, though. How old was the FPR when you cracked the diaphragm? Was the crack obvious?

BTW, I called AEM tech support and they didn't even know what a misfire was.