After several hours of trying to figure out why my car doesn't idle I've narrowed it down to a definite vacuum problem but a very wierd one at the least.



Symptoms: The car dies unless the driver holds the idle at about 1000 rpm or more with the throttle

If more than about 20% throttle is given it feels like the fuel is cut. Has more to do w/ load than throttle position

Cruises well though. (no hesitations of any sort unless in the conditions above)



So.......



I measured the vacuum on the nipple on the left side of the top of the LIM, I believe, (looking from the front of the car). It shows over 20 inches. It's still not running right. I take off the intake to see if may have missed something for lack of a better cause and nothing that I could see. So after assembly I start her up and the same old ****. I measrue the vacuum from a different area, however. It shows barely any, like 2 inches at most. Now this was measrued on the back side of the UIM where there are like 4-5 nipple forged in vertically. The other spot mentioned before still has vacuum (over 20 inches) but the other doesn't. This is really chapping my ass. Anybody have any ideas?



Thanks

I am by no means an expert, and I probably have no idea what I'm talking about, but I'll get the ball rolling here.



So, you have major vacuum in your lower intake manifold, but hardly any closer to your throttle body, right?

This may sound dumb (see above disclaimer), but could you have some kind of blockage in there?

Well if you are under throttle your vacuum readings will be different, it has to be at idle w/o the throttle depressed. You can probe with a piece of vacuum hose, which works pretty well.

I know it may not be totally accurate without the butterfly valves closed but such a change in pressure in the intake is odd, no? A pressure drop from 1 inch of vacuum to 22 is definitely a lot especially in such circumstances.

some of the vacuum line nipples go to different places. there are some that go in front of the throttle plates, and dont see the same vacuum signal. have you tried spraying the gaskets with carb spray?



mike

Nope, I just tightened the throttle cable a little and now it idles at 800 rpm perfectly. I'll probably adjust the throttle stop screw. The engine runs really smooth until it gets a certain amount of load. It seems like whenever the turbo starts to kick in it cuts the fuel. The turbo kicking in might just be coinsidence with the load. It usually happens at about 23% or more throttle according the the S-AFC.

sweet hopefully the throttle stop screw can get it where you need it.





you should check to see if the nipples being used for vacuum source for the boost sensor / FPR are getting vacuum before or after the throttle plates (use the vacuum gauge to see if it's high or low vacuum at idle)



that might be your problem with the bogging, if they are not getting vacuum after the throttle relocate them to a nipple that is.



I'm still confused why you are getting such low vacuum from that nipple we checked, perhaps it's getting vacuum before the throttle plates, apparently the nipples get them from different place although they are in the same location on the intake (internal passages leading elsewhere?)



good luck and keep us posted on how she runs https://www.nopistons.com/forums/pub...IR#>/smile.png





also anyone have a S5 T2 TID with no cracks? rmaiersg could use one https://www.nopistons.com/forums/pub...DIR#>/wink.png

check your timing



just make a new metal TID from a honda cold air intake pipe https://www.nopistons.com/forums/pub...IR#>/smile.png

I got the idle running smooth at around 800 rpm still need to work on the load situation. One of these days I'll have to make a TID.