My evo won't idle. When I am up to speed, if I hit the gas, it either bogs down or goes as normal. I'm unsure what to do. I brought it to mitsu and after 7 hours of looking at it they said to replace the fuel pump. I replaced it and it still stalls at idle, no change. Any ideas?

 

Unplugged MAS, works fine now. Will purchase new MAS.

 

you have an aftermarket BoV?

 

No. It looks stock to me. This is my second evo, the original owner of this one has done a little work to it. Intake, exhaust, boost controller... TRE transmission, some stabilizer bars that I haven't had time to identify (sway bars?)... a few other things.

No BOV though, why do you ask? Because it is definetly the MAS, does the MAS usually only go when there is an aftermarket BOV? When I unplug the MAS it runs fine with a horrible idle and cuts out around 4k rpm (granted I'm driving slow until I get a new one). I'm somewhat of a newbie, I don't know much about the MAS.

Do I have any other choices than stock MAS? Aftermarket MAS? MAS delete.

I've got a fuel computer now, an Apexi AFC Neo. Hasn't been put in yet, but I figure if I'm going to start modifying then I need to start with being able to regulate the modifications well.

Edit: I never saw much point in an aftermarket BOV with such little modifications that I have. Granted, with the right one, it would sound better... but sound means nothing to me. The sound of a stock evo is insane enough.

 

If its an 03 evo with the stock plastic bov ditch it, its horrible at holding boost. Also ditch the apexi afc neo and starting learning how to tune the fuel map via ecu flash, their is an entire forum dedicated and i suggest spending a good deal of time reasearching that topic.

When you said you unplugged the mas did you mean mass air sensor that attaches to the maf on the intake and you are now driving it with it unplugged?

If so i recommend you replug it and deal with a horrible idle, with that unplugged and driving your engine has no idea how much air is going into your engine besides what the map its tuned for and afc are "supposibly" telling it whats going in.

 

Can't replug it in, it was more than a horrible idle, it was not driving. It would stall every time the rpms were allowed to fall.

 

could be more than just the MAF sensor...could be BoV or other sensor issues, like the TPS sensor or IAC sensor

 

However it would appear at the heart of the issue is the MAS? Granted, there could be other issues, however with the MAS unplugged it works. So a new MAS should do the trick for now, yes?

 

Okay, new MAS didn't work. Also, now my car has no power. I can't even drive it, there is essentially no boost. Could all this be a bad BOV?