Cascade Crew

91RSVert · Posted: Mon Feb 06, 2012 10:28 am Post subject: High idle since cam swap.

So since I have done this cam swap, Ive been plagued with a high idle problem. After 1 day I found my breather wasnt plugged into the valve cover.

Been retuning and retuning. I figured this cam was just that much more effient but I have the desired idle/grams per second down to where a stock L31 is and still have fast idle.

Give me some ideas as to where I could have a massive vac leak that wouldnt show on a vac gauge, but I could be overlooking. Laughing

TPI
2002 van computer sytem
pcv on drivers side, valve cover to vac port on drivers side
breather on pass side. Valve cover to big port on TB.

Twilightoptics · Posted: Mon Feb 06, 2012 10:32 am Post subject:

Intake manifold.

Start spraying some carb clean around and see if you get the idle to change.

Sometimes you can have a leak on the underside of the intake, and if you don't have a closed pcv system (aka no breather to atmosphere) you can suck vacuum.

If you can't ID anything, clean your IAC, and lower your steps.

91RSVert · Posted: Mon Feb 06, 2012 11:08 am Post subject:

So your saying I may have not sealed my china-wall good enough? Wouldnt I leak a crapload of oil then?

Also saying temporarly remove my pcv/breather to verify that would be my issue?

your "lower your steps" is my "desired idle/grams per sec". Ive got that set to what a stock L31 is. I dont see how a tpi could be more efficent then it.

Twilightoptics · Posted: Mon Feb 06, 2012 12:16 pm Post subject:

-Not the china wall. The intake gasket itself to the ports.

-If you have a closed PCV system usually it wont exhibit as large a symptom because the air that it sees is already part of the plenum setup. It's not sucking air from the outside.

But if you have a standard PCV in one valve cover and an open element breather, then it can be a straight vacuum leak.

Yeah, see you've got a cam that was designed for another motor and another set of heads. SO you need to rule out mechanical issues, and tune it to what the motor wants.

91RSVert · Posted: Mon Feb 06, 2012 12:49 pm Post subject:

My "breather" is the elbow coming from the TB. I was thinking that if I didnt seal the china wall good enough(or timing cover too), that is a vac leak. But as mentioned, thinking it would spew oil.

I'm thinking if it was a small vac line, injector oring. That would cause my vac gauge to twitch.

My motor is a whole hinez 57...

Crate block
113 vette heads n base intake
91-92 plenium
aftermarket runners
LT1 cam, IAC
L31 pcm, dizzy, timing cover, knock sensor

91RSVert · Posted: Mon Feb 06, 2012 2:33 pm Post subject:

The ECM has my IAC all the way shut, says to remove .48lbs of air(thats about 4grams/ps). Which can not happen at all since the IAC is shut. Ive got a leak somewhere.

Twilightoptics · Posted: Mon Feb 06, 2012 2:52 pm Post subject:

Or your throttle blade is open too far?

91RSVert · Posted: Mon Feb 06, 2012 8:00 pm Post subject:

Ive got my PCV bypassed for tommorrow.

Did find out I have a small fuel leak on my return line.

chevymad · Posted: Mon Feb 06, 2012 8:03 pm Post subject:

Another trick that sometimes works to figure out if there's an internal vacuum leak. Remove the pcv from the valve cover. Plug the breather on the other cover. Plug the pcv hole with your thumb. If there's a leak to vacuum under the intake it will pull a vacuum on your thumb. It may take a minute or 2 for the vacuum to build up enough to feel it.

Another hard to find vacuum leak is the brake booster. Block off that line to eliminate that.

91RSVert · Posted: Tue Feb 07, 2012 5:09 am Post subject:

PVC system had no effect.

Tried the thumb over the breather holes in the valvecovers. It is blowing out for sure.

Tried squirt WD40 around the injector bungs. No flare up.

91RSVert · Posted: Tue Feb 07, 2012 10:11 am Post subject:

It also decided to form massive oil leak today after being together for about 200 miles. It has puked 1qt in 10 miles. Coming from up top, rear of motor.

IROCDave · Posted: Tue Feb 07, 2012 5:58 pm Post subject:

Like mentioned before, spray carb cleaner, propane, starting fluid etc around the top of the engine. Dont spray the plug wires or cap. If the idle picks up while spraying the highly combustible aerosol fluid you found your leak. This method will not identify an internal leak however.

91RSVert · Posted: Tue Feb 07, 2012 6:00 pm Post subject:

ok, think I found my vac leak(s).

2 of my runner gaskets are so far miss-cut that they are not sealing.
1 bolt that some idiot forgot to tighten Rolling Eyes

Still cant find oil leak. Wondering if this gasket that came with my brand new dizzy is a pos. Only 2 things that I know leak oil like this on top rear of motor is dizzy or the opsu plug which is effing tight and half covered with silicone anyway Laughing

chevymad · Posted: Tue Feb 07, 2012 6:13 pm Post subject:

Distributor only has oil splash at that gasket. Wouldnt beleive it possible to leak that much oil from it that fast.

Dewey316 · Posted: Wed Feb 08, 2012 6:49 am Post subject:

Oil Pressure sender or china wall would be my guesses for oil leak places.

91RSVert · Posted: Wed Feb 08, 2012 10:30 am Post subject:

OPSU is on the side of the motor.

Alphius · Posted: Wed Feb 08, 2012 1:12 pm Post subject:

91RSVert · Posted: Wed Feb 08, 2012 4:52 pm Post subject:

MrMike98 · Member Joined: 18 May 2010 Posts: 231 Location: Bremerton

My guess would be the rear china wall area, given that an intake gasket is out of place, that makes the rear seal very difficult..

or/and if the PCV system is not working correctly it could pressurize the crankcase and blow out the weakest seal..

good luck

91RSVert · Posted: Thu Feb 09, 2012 6:09 am Post subject: