Hey guys seeing if anyone can shed some insight on the problem I am having. Recently I picked up another evo 8 and the kid before me had the battery in the trunk kind of half assed rigged. One really cold night the car wouldnt start at all and the ground wire that was ran to the trunk just fell off so I relocated the battery to the front of the car. Well the factory Ground that hooks to the negative battery had the end that attaches to the battery cut off so I ran another ground wire from the frame rail to the battery. Ever since then Im having an on and off issue where when IM driving on the highway around 70mph it will randomly shut off one injector(Im assuming) and run lean and stutter wideband shows 21 afr. If I let off and full throttle the car its fine and goes back to normal sometimes other times it just keeps on stuttering.


Ive checked the tune and its fine but just incase i resorted the car to a factory base map (the car just has a turboback exhaust stock cams etc.) Still the same issue. I replaced all four injectors with a spare set I had and still the same issue. Replaced the fuel filter, Fuel pressure regulator, spark plugs, coilpacks, wires, and Fuel Pump still having the same issue. I even replaced the Injector resistor pack since I had one off my Evo 8 that ran ID1000's and STILL the same issue. The only other way I can describe the problem Im having is that it sounds like its running on 3 cylinders when it does this "miss" except it runs lean not rich like it would do if it was "breaking up". Ive checked the timing belt no issues, even did a compression test and a leak down test and its perfect, I have NO idea what else could be causing an injector to just randomly stop working when Ive already replaced them. ANY HELP WOULD BE APPRECIATED.

 

Also I want to mention there is no CEL. So the whole p0300 issue isnt whats going on even though it seems like that would be the problem

 

No input guys? come on I know someone may have an answer and Ive done ALOT of searching

 

I just saw you posted on my thread too. I was reading this post and I was like.. this sounds like what I'm going through lol. Do you have a cop setup? I'm wondering if its just my wiring that is the problem.. I'v also replaced my fuel pump and new coil on plugs. We need to figure this out man. I don't want to be worried to drive on the freeway. One thing similar is I have my battery relocated to my trunk also and when I did it i just used a 2ga audio wire for the power and installed a 200amp inline fuse in the power wire near the battery. Not sure if that could cause it? Maybe I don't have a strong enough voltage with the 2ga wire?

 

you did pretty much all of what I can think of, maybe a bad batch of gas?
If not I would check back the wiring of the injectors could be electrical as well.
sounds like a fuel issue for sure.

 

I would double check all the wiring and pay close attention to your grounds. Also wouldn't be a bad idea to check the voltage on the injector harness. Another thing to check would be the FPR. May not be a bad idea to log fuel pressure to see what its doing when it starts acting up.

 

The stock ground wire goes from the starter to the alternator to the frame rail to the battery. It might be useful to just try to find the oem grounding harness from someone on here and see if that helps.

 

check fuel pump basket. There is a black rubber o-ring/gromet in the hat that could have a rip in it. Ask me how I know...

Car goes lean and will basically only idle due to low fuel pressure. The pump basically just pumps fuel straight back to the tank and not to the rail.

 

http://www.streettunedmotorsports.co...nk_grommet.htm

above is the part I had to replace.

 

There is also an o-ring on the fuel return orfice side. Might want to check that as well. Those tend to come off the shaft and remain in the housing. When putting back together fuel can then bypass the orfice i believe thus creating low back pressure for the fuel system and the pump can not pressurize the system.

I also caught this, but the car wouldnt start without this o-ring.

 

Alright guys sorry for not replying back and thanks for the responses. Well I feel like an idiot and actually kind of annoyed. So the previous owner of my car decided to pull the check engine light bulb out of the gauge cluster and BEHOLD p0300. I disabled it and the car runs like a champ. Im using an open port 2.0 cable and evo scan cant read CEL's anymore. Go figure.

 

But still doesnt change the fact that the p0300 being disabled would fix the problem since it doesnt happen everytime I drive the car. I will go and check all the factory grounds in the vehicle. again thanks for the help