TBIThrottle Body Injection discussion and questions. L03/CFI tech and other performance enhancements.
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Recently, I installed a larger bore (46mm) TB unit on my camaro.
The unit has a rebuilt throttle shaft with new bearings and no play in the shaft whatsoever.
After first installing the acclerator was hard to depress, and I came to the conclusion that the throttle blades were sticking at idle (a fairly common problem), I adjusted the IAC to prevent the blades from closing completely and the throttle can easily overcome the vaccum and the accelerator easily depresses and take off is smooth.
Now, the odd problem I am having is that the throttle sticks after speeding up to any regular speed and letting off the pedal. The car will hold the rpms steady or slightly decline, almost like the cruise control is on. If you quickly romp the throttle it breaks the sticking free and the rpms drop like they should, but not if you just let off the throttle.
Is this a matter of the blades getting physically stuck at higher rpms or that there is not enough vacuum to pull the blades back closed or is it just a faulty throttle shaft?
ANY SUGGESTIONS, OR ANYONE HAVE THIS PROBELM BEFORE?
The vacuum actually makes in harder for the throttle blades to close as there is alot of force on the blades when vac is present. Combine this with the TV cable and throttle cables pulling on it, and the throttle may not close on its own.
Check to make sure that the throttle cable isnt under tension when the throttle is closed. If it is, then slightly elongating the eye in the throttle cable end might help.
Throttle cable isn't tight in tension when they throttle is closed. I have heard that there is a spring that can be swapped to allow the blades to close quicker, but this was for a carb? You think that could that be the problem on a TBI?
Throttle cable isn't tight in tension when they throttle is closed. I have heard that there is a spring that can be swapped to allow the blades to close quicker, but this was for a carb? You think that could that be the problem on a TBI?
With the car shut off, close the throttle all the way by hand and make sure there is still a very small ammount of slack in the cable. Its likely to be fine but with the manufacturing tolerances of some of these parts things can be a little off sometimes.
The spring is easy to install. Clip it to the throttle shaft and to something else nearby thats stationary and thats it.
Sounds to me like the 46mm TBI has some machining faults. Maybe the bores aren't perfectly round or the right diameter. Maybe the new bushings are too tight. Maybe the line boring slightly shifted the shaft out of center...
From all I can tell the bores are very precise (no rubbing but no excess space between the blades and the bore). The throttle shaft is brand new and also doesn't seem to have any play in it. As far as the bushings being to tight, I'll have to tear the air breather off and check again.
I've only heard good things about this guys TB's unless this one just has an error. It's a kit form Xtreme-FI.
Just pull the throttle cable off the linkage and see if you can pull it further. The gas pedal will move up as you pull past the closed throttle point on the cable. I highly doubt that's the issue, considering this TBI is based upon and still highly resembles a stock TBI.
Double check that the return spring on the TBI unit is clean and free of funk. That spring will corrode a bit and create all kinds of funk in there that impedes the movement of the spring. A few hits with carb cleaner and a toothbrush can make the TBI operate much smoother. I would add a small drop or two of clean oil to it as well to ensure that is stays lubed.
While I was checking everything out I decided to adjust the TV cable properly because I was getting extremely late shifts.
The good news is that the throttle no longer sticks (maybe TV cable was in too much tension), and shifts are where they should be.
The bad news is that I have no 4-3 3-2 4-2 downshifts whatsoever, even at WOT. (The reason I used a rebuilt stock TB was so that all the linkage would be correct so it is my understanding that the TV cable is set correctly)
If you were getting late shifts before and no kick down now i would guess cable is not adjusted properly. btw if any one starts building big power and has the throttle stick, have your hand on the ignition key ready to shut it off before you go blip the throttle. I know a guy that was in a full body cast and laid up for months because he did this and the throttle decided to stick wot.
Throttle just starting sticking again, I am still battling the transmission/tv cable issue but it seems to have noe bearing on the throttle sticking/hanging rpms.
I don't see how the uneven wearing can still be a factor is the shaft and bushings are new.
I considered using a light carb return spring(but I needed some pics of how this is set up first)
I know this thread is old, but I was searching for a cure for my problem which seems to be exactly what yours was! I just put a built 350 in my 92 RS and have the same problems you described as "throttle sticking after speeding up to any regular speed and letting off the pedal. The car will hold the rpms steady or slightly decline, almost like the cruise control is on. And if I "quickly romp the throttle" it breaks the sticking free and the rpms drop like they should, but not if you just let off the throttle. Further more, it actually speeds up more! WHAT WAS YOUR CURE!!!
I am just reading it now. Well mine did the same thing you need a new spring on the throttle or heavier spring. Because its not springing back closed fast enough. It might be b/c the spring is also stretched. I would say go get a new one don't bother messing with the old one. You will see a difference.
I know this thread is old, but I was searching for a cure for my problem which seems to be exactly what yours was! I just put a built 350 in my 92 RS and have the same problems you described as "throttle sticking after speeding up to any regular speed and letting off the pedal. The car will hold the rpms steady or slightly decline, almost like the cruise control is on. And if I "quickly romp the throttle" it breaks the sticking free and the rpms drop like they should, but not if you just let off the throttle. Further more, it actually speeds up more! WHAT WAS YOUR CURE!!!
Then why at the same time, are you posting statements like this in the other tread?
Quote:
Originally Posted by 92Vortec
I`ve been happy with mine so far. It has only been in for 1 month, but so far so good. It is a ported (50mm) Rochester TBI 220 stock unit. Flows 700 cfm. Great unit! they also have a really nice pressure regulator for only $40. I got 9C1 injectors from them, too. I`m running imine with a Vortec headed 355 with LT4 Hot Cam & 3.23`s. I used to be an L03 car. I don`t even have 500 miles on the motor yet! http://www.xtremefi.com/QA.htm
The TPS effects the throttle follower. If the ECM thinks the throttle is open, it will retract the IAC to provide additional airflow when its not needed.
cause it's not actually the throttle sticking but the tps makeing the ecm think the throttle is open and turning the whole system stupid and keeping the engine at a higher rpm.....fix: new tps or BFH and wish it the best a luck lol
