Hey guys,


I just started to experience this trouble with my Evo 8 when temps here in Atlanta got colder maybe 2 months ago. The car idles and drives flawlessly when driving like a sane person. It shifts correctly -no misfire, no hesitation and no codes of any sort. The problem only arises when I accelerate really quickly like we all know and love Evos do easily. I noticed the lose in power(BOOST) happens when I'm in 3rd gear, but it has happened once in 2nd gear.


When I accelerate HARD rowing through gears there is no pops,bangs or any misfire....its butter smooth. Just my fat low end torque I'm used to is significantly lowered like its going in limp mode. When that happens I let off. Any the evo continues like NOTHING happens; Any ideas? I changed my plugs early in the summer, no whine from fuel pump. Could I need new spark plugs?
*The car has S2s, walbro, PTE 1200s and all bolt ons. It is tuned, and been on this tune since 2010 no problems likes this.

 

Have you done a boost leak test?

 

I haven't, also forgot to mention it does feel exactly like a IC pipe popping out.

 

Did you take a look at the IC piping? lol

 

I would start with a boost leak test

 

could be a slight one that doesn't present when boost is ramping up slowly but will open up when letting her rip.

 

Like a dummy I didn't.

Thank you for the advice, instead of doing boost leak test once every oil change, I will move it to at least once a month.

That's a great analysis H., sounds like I need to re-adjust my couplers or replace my worn out t-clamps.

 

My compressor is always ready for boost leak tests, I do them about every month. You can spray some hairspray on the inside of the couplers, its supposed to act like a glue.

 

So I did a boost leak test this weekend and went over all my piping with the method you mentioned(hairspray) I think it worked great. I was able to find minor leakage near throttle and another at j-pipe, however it turned out my limp mode was caused by this:


NOTICE: the silver-ish ring around the sensor, the ring "cap" in my Buschur air filter came loose and partially blocked the sensor hence causing the limp mode to kick in.

 

But how this is possible if filter goes over the adapter?

 

Here is a picture to show the design, I think mine was the gen 1 Buschur air filter. The glue residue can be easily be seen flaking off. They make great products, I bought mine used from a filter which looked absolutely new, its probably the heat under in the engine that enhanced it to deteriorate...


Second picture is the exact filter I got which I got from google.


In addition, I don't believe I went lean at all just the computer went to limp more immediately. I'm kind of glad the maf is there because I had plan on going speed density.

 

Oh makes sense now ,thanks for clarification .but damn for ppl with speed density it could be disastrous

 

Not exactly limp mode, but the MAF sensor was not seeing the correct airflow over the little element. The car was unable to determine that air was actually passing through.

 

That little cap would of easily been chewed up.....talk about juicing the wrong thing.

Correct, but it was the closest describable feeling, I would also like to add my limp mode when LICP blow off causes the car to break up and rpm will not pass 2000rpm or less, this didn't - I will likely get a new MAF