fd3s20b

I was just wondering if this was most likely caused by this "monster port" that the previous owner had done? Or is this just a matter of tuning?

My car idles at 1700rpm and only pulls 8" of vacuum. I read somewhere that a healthy motor should be pulling 11" of vacuum and even bridge port motors are only idling at 1500rpms. So just curious as to what all you rotary gurus think is the problem.

DaleClark

iTrader: (55)

First, you can't really read vacuum to compare unless at a 850 or so RPM idle.

Find out why your idle is so high - either the throttle body is open too much, the ISC is stuck, settings in the PowerFC, or a vacuum leak.

No sense idling THAT damn high even with a big port job. That's just sloppy work.

Dale

fd3s20b

Yeah it gets a little annoying sometimes with such a high idle. What exactly is a ISC and where is it located?

zman600

iTrader: (5)

ISC = idle speed control. its on the upper intake manifold. back side/underneath.

looks like this
http://www.rotaryresurrection.com/kl...y/DSCF4435.jpg

take it off and clean it out with electric parts cleaner. turn it on with some liquid in it too while it off the car.

but before you do anything like this....
first, look for vacuum leaks after the throttle body. and check the power fc idle speed

if that all good

then, try to adjust the idle with the adjustment screw on the throttle body and the bleed screw under the throttle body. (cant find a good picture of this)

after that then take off and clean the ISC.

if still there is a problem then come back here lol

fd3s20b

Sweet, thanks for all the help.

fd3s20b

Looks like my idle speed control valve has been removed. There is a block off plate there instead. Would this cause my high idling?

DaleClark

iTrader: (55)

With no ISC you have hard idle control. The throttle body's set screws are probably messed with to bump the idle up.

Here's the deal - engines need air to run. If you have ZERO air going to an engine, it won't run, period. To set an idle, you give the engine just a little trickle of air, just enough to get the RPM you want. The engine doesn't care how the air is getting in - throttle plates open, vacuum hose off, hole in the side of the intake manifold, doesn't matter. The more air the engine gets, the higher the idle. You have to find how the air is getting in and reduce the amount.

I prefer to have the ISC on a car as that is a nice, precise motor that can adjust the amount of air the engine gets to set the idle. Most people take it off because they think they're cool .

Dale

fd3s20b

You hit the nail on the head. First I set the air adjusting screw and found that it was already set to a 1/4 turn out. Next I adjusted the vertical adjuster to the right of the throttle body up so that the throttle could close more and this brought the throttle down to a much more bearable 1200rpm.

zman600

iTrader: (5)

good to hear.
sounds kinda like you still have a vacuum leak somewhere after the TB. are you able to lower idle more then that? or is your TB 'closed' all the way

if its closed all the way and your still idleing at 1200 you most likely have a vacuum leak somewhere.

fd3s20b

Yeah I just adjusted the throttle screw again just to be sure. i got it down to 100rpm and that is fully closed so most likely I do have a vacuum leak. I will have to check tomorrow. Thanks for all your help.

Radial GT

iTrader: (16)

Also check to make sure there is no tension on the cruise or throttle cables. Either of those will hold the butterflies open if there is tension on them, and lead to high idle.