TOP END REFINISHING

[Schrade]

AND my IAC block; a 13mm socket with masking tape came out MUCH easier than it went in.

So that might account for the lope when it went CL, warmed up, with IAC bore opened up by heat. But it still never went below 875, OL or CL...

[XfireZ51]

Yeah so I think it may be time to look at how the throttle blades are situated in the bore. It doesn't take much.
You removed the primary throttle as well as the secondaries? Can you try pushing on throttle lever itself to see if you can close throttle further manually?

[Schrade]

Originally Posted by XfireZ51

Yeah so I think it may be time to look at how the throttle blades are situated in the bore. It doesn't take much.
You removed the primary throttle as well as the secondaries? Can you try pushing on throttle lever itself to see if you can close throttle further manually?

I did NOT remove the primary shaft or the primary butterfly.

I cannot manually pull the secondaries closed any further.

Just got off of the phone with Marc; he suggested something I had actually thought of - blocking the secondary ports in the TB. He said if rpm's then go down LESS than 100 rpm's, then the TB is fine.

If the rpm's then drop MORE than 100 rpm's, then it needs attention.

[XfireZ51]

Originally Posted by Schrade

I did NOT remove the primary shaft or the primary butterfly.

I cannot manually pull the secondaries closed any further.

Just got off of the phone with Marc; he suggested something I had actually thought of - blocking the secondary ports in the TB. He said if rpm's then go down LESS than 100 rpm's, then the TB is fine.

If the rpm's then drop MORE than 100 rpm's, then it needs attention.

Makes sense. Have you checked throttle blade clearance in the bores? Also, if you have motor running and blip the throttle, how does motor behave returning to idle?

[A26B]

I'm going out on a limb here.....

Before you remove your "ticket stopper"

unplug the TPS to keep it out of C/L just to see if the ECM is inducing the idle speed based on errant readings, such as vacuum leaks. An engine can still run pretty smooth, although idling high from vacuum leaks.

Assuming the idle speed is still high, start checking for vacuum leaks in not so normal areas, using a propane torch with a rubber hose on the end (remove the burner tip & put the rubber hose on the small pipe from the valve)

Check around each injector where they fit into the injector housings, the T/body shafts where they fit through the throttle body, the Dual PCV hose system, from the inj hsngs, all the way into the plenum, the connectors to the 2 hoses into the plenum under & behind the t/body area...... and anywhere else you can get to, including all of the intake gaskets joints.

[Schrade]

The 'Ticket Stopper' dropped my rpm's to 475, STEADY. although rough, like a cammed motor.

Looks like I blew the TB re-assembly. I could NOT see light through the secondaries, but, the Ticket Stopper doesn't lie.

I'll cut out the IAC opening, and see how that effects idle, before shipping the TB off to Marc for a re-work.

Thanks again there Dom, for the phone time there - LOOKS like this thread is about ready to close.............


ed.:
Just saw your post here Jerry; got it. Should I leave the IAC port blocked as well, before doing your test? She would barely run as it was, and actually DID cut off after about 7-8 minutes, while on the phone with Dominic there...

[mike100]

I could probably use a rebuild on my throttle body also, but my solution was to restrict the PCV hose back to the plenum. I y-ed the hose circuit to a filtered can so the PCV can still flow out in volume during hard accel. But it did drop the rpm's 100 or so at idle and got some positive IAC counts.

seems to be a common thing on these engines.

[XfireZ51]

Sounds like an LT-5 idling. Who knew?

[A26B]

Looks good! Glad you are getting it sorted out.

[Schrade]

...and then again, perhaps I did NOT blow the TB re-assembly.

I pulled it, and took a close look in the TB 2' bores. There was some particulate jam HOLDING OPEN THE SECONDARIES, surely enough for a vac leak through them... And I had never worked the 2' s, such that they pulled through.



Looked like tiny grains of sand, Black. Where it came from, I cannot guess. I thought I had every little piece spotless sterile clean since the beginning. Even conscious of grit falling off of my sweatshirt sleeves (you learn about that when you spend 5 weeks polishing a Black '94 by hand - 2000 grit, rubbing compound x 3, polishing compound x 4, 5, wondering where new swirl marks come from).

So the TB is re-cleaned. Ready to bolt back together again...