I think I found my surging idle problem

[Burbdood 74]

So, for the last couple of years, I've been dealing with an intermittent surging idle on my 88 Burb. I've chased down the EGR, EGR solenoid, checked for vacuum leaks, done just about every thing I can think of but to no avail.

So, I noticed the other day when I pulled into the drive, the idle was perfect. I had to back up over the edge of the concrete and I blipped the throttle and immediately it started to surge. I stepped on the throttle and gave it a little gas and smoothly took my foot off the pedal and the idle was perfect again. I was able to do this 3-4 times in a row.

So my thought is, and correct me if I'm wrong, is that the throttle shaft bushings on the TBI are worn out, the throttle blades are sticking slightly, and it's causing a vacuum leak and thus, it's surging. Am I on the right track or am I way off base?

 

[rampage]

I'd check to see if the throttle cable is sticking in the sleeve that it rides in. Sometimes the cable wears a groove in the sleeve, or it just may need to be cleaned and lubed.
Disconnect the throttle cable from the TBI unit and manually operate the throttle blades and then the cable to see which is the culprit.

 

[4X4HIGH]

If the throttle shaft bore is worn it would run the same ALL the time, there is no way of making the shaft seal for a minute and then not seal again.

 

[454Sub]

Im betting your problem is either the throttle cable not letting the throttle close all the way, or the throttle shaft bushings are worn. Something else just popped into my mind, are the throttle plates themselves tight on the throttle shaft? I remember when I was porting mine, I had to get them lined up just right for it to close all the way, and one of them moving around could cause it to run awkward. Either way I think you have narrowed down your search to a small area.

And maybe it is possible for that throttle shaft to shift slightly in its bore to both seal and unseal it, you never know with vehicles, finicky like women sometimes.

 

[Burbdood 74]

Looks like I've got me some more investimgating to do. But I do believe I'm on the right path since I can smooth out the idle with just some manipulation of the throttle. I do believe I will work on the throttle cable this weekend, (I never thought of that as the culprit so thank you guys for that).