Leaking TB
Thread Starter
Intermediate
Joined: May 2011
Posts: 44
Likes: 0
From: Michigan
Leaking TB
So my '94 LT1 powered corvette has had a rough, rolling idle for a couple of years now, but since I don't drive it much I haven't bothered dealing with it until now. I replaced every rubber hose, plastic line, and fitting I could find connected in any way to the intake manifold. I also removed the TB, cleaned it, and replaced the gaskets. But it still idles rough. Figuring it is a hard-to-find vacuum leak, I did a smoke leak test and found a lot of smoke apparently blowing out through where the throttle shaft goes into the TB, on the driver's side, behind the coiled return spring. Only thing I can guess is the throttle shaft bushing is no longer sealing. Is this a problem anyone else has noticed, or am I probably wrong because that kind of issue is basically unheard of? But if it likely the bushing, what's the best way to fix it? Rebuild? Send out for rebuild? Buy new replacement? Aftermarket replacement? Thanks!!
Intermediate
Joined: Jul 2013
Posts: 33
Likes: 0
From: Wickenburg, AZ
same results on my 90 L98
So my '94 LT1 powered corvette has had a rough, rolling idle for a couple of years now, but since I don't drive it much I haven't bothered dealing with it until now. I replaced every rubber hose, plastic line, and fitting I could find connected in any way to the intake manifold. I also removed the TB, cleaned it, and replaced the gaskets. But it still idles rough. Figuring it is a hard-to-find vacuum leak, I did a smoke leak test and found a lot of smoke apparently blowing out through where the throttle shaft goes into the TB, on the driver's side, behind the coiled return spring. Only thing I can guess is the throttle shaft bushing is no longer sealing. Is this a problem anyone else has noticed, or am I probably wrong because that kind of issue is basically unheard of? But if it likely the bushing, what's the best way to fix it? Rebuild? Send out for rebuild? Buy new replacement? Aftermarket replacement? Thanks!!
I, too, just did a smoke test to look for a vacuum leak. I've had a high idle (1100-1500 rpm) on my 90 L98 manual coupe with 103K miles and I assumed I had a vacuum leak that was supplying a little too much air. If it gets a little too high at a light I can "kick it down" so I wondered what kind of vacuum leak would act like that. I did my smoke test and noted smoke coming out of the TB at the bearing near the cable connections. From what I have read so far, there is no replaceable bearing or seal behind that.
Did you have your TB reman'ed or bearings installed? did it fix your problem?
