OK so drove down the shop yesterday in my evo vii and all was good, turned it off and when I came back and started the car I noticed a slight shake at idle. When I got home and listend to it I noticed it sounded like it had some lumpy race cams ( it doesn't) but still idles at 800-900 rpm and doesn't drop below just kinda stumbles (again sounding like race cams). I searched for vacume leak's and found one small one at the throttle body shafts but from what I hear the ecu is quite good at compensating for this. So I took off the throttle body,maf and idle control valve for cleaning(all filthy) but upon reassembly still the same poor idle. The idle control valve I noticed had play in it about 2-3mm on all directions includeing rotation at the tip, I'm not sure if this is normal? . I'm getting no fault codes and the car still drives smooth this problem is only at idle. Anyone out there have any advice it would be much appreciated. Oh and at idle I'm getting .4 bar vacume again is this normal?.
And thanks again in advance for any help guys.

 

Anyone?

 

The only way to do a proper boost leak test is to actually pressurize and hold the entire system at or slightly higher boost level at where the car is tuned. Did you really do that?

 

Would a boost leak cause this idle? Car drives perfect both on and off boost. Ps it's only really starting when the car is warmed up

 

Yes it can

 

ok thanks . And as for the idle control valve should the tip of that have play in it

 

Not sure about that one

 

OK thanks anyways. Appreciate it

 

could be alot of things, but I would hold off tearing it apart until you get another full tank of gas through her. If she is still having troubles or if a code or something pops up then start digging. Also if any regular maintenance is lacking, like spark plugs or something, then it would probably be a good idea to get ontop of that.

 

Put a new tank in her yesterday and drove a bit maybe for a half hour ish came home and when I stopped idle was the same. I'm getting no codes still. And plugs look good. Completely stumped. ..

 

It shouldn't have any play.

 

So if I got this rt, .4bar is about 6 psi vacuum...that's way low, you don't drop vacuum unless there is a leak---which has been pointed out or the cams are out of phase or moving--so you have a good timing belt and its ben changed at the correct intervals an no noises from that area? I wouldn't think if it was the IAC you would have a sporatic idle, up and down and then idle would be around 500 rpm...so I don't think that's the prob. As for driving ok, the leak causes a rich condition so I would assume outside poor mileage it runs great.

 

OK so I must have a leak this evening I tried the spraying carb cleaner method to try to find the leak to no effect. What vaccume roughly would be the norm?

 

18-22 would be normal variance depending on what accessories are on and stuff

 

18-22 inhg? About. .6 - .8 so ya there must be a small leak. I think I may have found one at the throttle body shaft hopefully that's it.