Okay tonight my buddy asked me to take him for a ride in my evo (he's never been in one).

Ripped it up and down the road like 3 times , 1st time ripped it down the road , 2nd time 2 step launched it , 3rd time 2 step launch again. Car was running mint. Pulled it back in the shop , let it cool down everything mint, perfect idle reved up smooth.

after about an hour i jumped into my car and started and idle was very chopping , didn't think much and started pulling out and car was very very chopping. stopped and when reving it at a stop light it was reving slow then at like 3500 it reved up quick like normal. Got on high way wide band was reading very lean while speeding up building like 2 or 3 lbs of boost. afr was like 14 / 15. I went back to the shop. Checked plugs and they were white from running lean i am assuming. disconnected battery to rest ecu , reflashed it with org. flash , checked all hoses and plugs and couplers aka everything. It was all good under the hood of the car. took it out of a rip was the evo scan going , no ecu code , but knock sums under load hit 8/9 jumping to 38 and once hit 59. i let off when the knock light went red. on highway under slow accel/let boost come on slow , afr acts pretty much normal. but i go to punch it full throttle hits 16.00 afr , but then let off goes rich then back to 14.5 afr.

So i added some fuel system cleaner and fresh tank of mobil gas and still same thing. car was also at 1/4 tank of gas when beaten the **** out of it.

It has walbro 255 and new filter installed in june 08.
perrin fuel rail
pericsion/ams 780cc injectors
car is professional tuned and has run mint for the 6 or so months it has been tuned.

So here are my thoughs:
clogged fuel filters
stuck/clogged fuel pressure reg.
bad o2 sensor
dirt in the injectors
fouled out plugs- runing bpr8eix been in for about 7 months.

 

hmm weird sounds like clogged injectors.. i say weird cause this happend to 2 of my friends in the past weakk same type of symptoms..

 

well we are going to pull the pump and other pick up from the tank and replace both filters. take off the injectors and blow out the filters on the injectors and see what happens. Were going to test the o2 sensor also.

 

Could be the o2 but fuel also, keep us posted

 

wow no one else with some helpful advice.

 

how are you logging knock?

 

throw evo scan

 

oh crap im also having this exact problem just today, full throttle afr leaned first then go rich then only normal, idle even went lean at times and stalled, my walboro whined abit funny when this happened, could it be the walboro failed? i just had them early this year.

 

You do realize that knock sums will never read over 36? Check compression, you may have cracked a ring land or lifted the head.

 

I figured it out awhile ago. The stock fuel pressure reg. was sticking.

 

Hey matt I got my hands on a free evo 9 turbo with like only 4,000 miles. Some guy dropped off a complete evo 9 head with valve cover , cams all sensors and attached intake mani with all sensors and throttle body with injectors , 4 rotors and 4 cailpers with raditor too. All for a some work on his evo with a quick tune. I think all this stuff is hot cause every wire and hose it cut like they were in a big rush to get it out. But Ya got a evo 9 turbo dropping in with my new clutch , and fixing my major boost leak down at the lower inner cooler pipe flang at the turbo.

 

MrEvo2nv,
So your problem was your Fuel Pressure Regulator failed?

 

i am having same issues...please shed more light on this

 

seems to be a common issue with those using walboro?

 

I guess...I am running walbro pump as well. My problems started a while back on stock injectors but would only do it every once in a while and would stop once i completely backed out then applied throttle again. (unsticking maybe) Since I upgraded injectors it is terrible so I haven't driven the car much. I am showing exactly same thing as the OP. MrEvo2nv did you just replace the fpr?