hey guys, ive owned my evo 8 for almost two years now and when i first got the car it was running in the neighborhood of -20 vacuum at idle. then a couple months ago kinda out of the blue it dropped down to around -14 to -13 vacuum at idle. i just went through my entire intercooler piping sytem, replaced all clamps i could find, did a boost leek test for good measure, and replace a couple of old looking vacuum lines. i cant find where i would have a vacuum leak and i was wondering if anyone would know of any suggestions of where to look next. thanks alot guys!

 

Did you install cams recently?

 

nope, no modifications or changes were done.

 

Have you checked the lines running to the EGR?

 

those were the first lines i checked and they were all in good shape and where they belong

 

Is your A/C ON when this happens

 

no its showing the same regardless of the ac... Its gotta be a vacuum hose hiddin somewhere thats leaking...

 

boost leak check the car

 

i already have (twice) as i said in my original statement

 

Do you know what cams you have? And what RPM does the car idle at?

 

stock cams. and i think it idles right at 1k ill edit if im wrong once i go double check

 

compression test
if compression is low, vacuum will be low... sometimes

 

I had this happen to my Evo. It just started to idle low and the vacuum dropped to -14 from -20. The car also sounded like it had a cam when my car is stock. My air fuel ratio stayed at 14.7 - 15.1 while this was happening. I fixed it by disabling the EGR through the pcm, there is a write up in the how to section. Hope this helps you

 

Check with another gauge. Theres probably a leak somewhere. No reason it just randomly starts pulling less vacuum.

 

It's also possible that your timing belt jumped a notch. That will throw off the vacuum. That happened to my Civic not too long ago.