I started my rebuild yesterday after many months of anticipation. After the smoke and rough running it settled down to a 750 - 2000 rpm surging idle. TPS is adjusted, BAC makes a even cycling noise with the key on and all looks OK.

I pressureized the intake maifold and shot a soapy water solution around the potential leaks points and found that the throttle body butterfly shaft blew bubbles at each end. This could be my surging idle problem!

I had done the throttle body mod and left the dual butterflies in place, so no plugging of the shaft was required. I did notice that the shaft felt loose and thought that it might be a problem. Installed it anyway.

My question is, has any one had this issue? It appears that it's just a clearance fit between the shaft and the body bushing. I didn't have any orings left over after assembly. Do I need to get o-rings, grease or new bushings.

 

Grease applied from the outside did not work. Still blows bubbles.
Definitly a throttle shaft leak. Time to pull the TB.
Has anyone ever repaired this? I'm looking for info on new bushings/seals.
I may have to just pull the shaft/butterflys and plug the holes.

 

i had the same problem, i just did the ReTed TB mod. since that was the shaft that was leaking.

 

that shaft leaking is an acceptable leak, if you look at the thermowax passage you will see it is vented to the atmosphere. disregard any leaks at the throttle pivots unless the shaft feels escessively sloppy like the bushings are severely worn.

technically there is no vacuum at that point anyways since it is just prior to the plates, it would however create a tiny boost leak in boosted motors, not enough to cause much headache.

 

Yes, I noticed the gasket air channel on the thermo wax side. The opposite side is just a shaft to bushing clearance fit. It too blows bubbles. Overall, the shaft slop isn't that bad.
I was goint to pull the TB today and remove the first set of butterflys and plug the holes but now I'm still at a loss for the surging idle.

 

surging idle is usually a combination of of a misadjusted TPS and BAC.

 

The TB is almost off, so I'm going to remove the butterflys and plug the holes. It will clean up that area too.
I have the TPS set at 1.0V and one light on. I think this is correct. I'll check the resistance sweep also.
Do you know what the intial set of the BAC screw should be? How many turns from seated? As long as I have been checking this forum, I never came across that little factoid.
The BAC makes a cycling sound when the key is on. I think this is a good thing, however, adjusting it while the engine surged did nothing. I disconnected it also and had no effect. I suspect what ever is causing the surge is beyond the BAC adjustment.
Pulling the TB will also let me cap the UIM so I can run some more pressure test and check around the injectors for leaks.
Thanks for your replys, I'm so close to being back on the road.

 

try adjusting the TPS while the engine is running and see if the surging goes away, some engines just do not like the 1 volt setting.