BTB Failure

[tann3r]

Well after a solid year if tracking my FFS '99 I've had my first failure. The throttle body shaft sheared off at the screw where the butterfly and shaft connect.

It broke while I was out for a evening cruise with some friends. I noticed the throttle sticking slightly open when rolling out of the gas as well as a slight intermittent vibration in the gas pedal. TPS was reading 1-2 instead of 0. Stopped at a gas station and started playing with the BTB linkage and it came right off in my hand. I immediately looked at my friend and said "that cant be good." I checked the 2 butterfly screws, thankfully they were still in place and were not eaten by the blower or my motor. Well a couple zipties later and I limped it home and called it a night.

http://lh4.ggpht.com/tann3r/SN0dHhWM0bI/AAAAAAAAB64/-qVGjgUdozM/s800/IMG_0227.JPG

This morning I ventured under the hood to see what exactly went wrong. I'll let the pictures do the talking.

http://lh4.ggpht.com/tann3r/SN0dIY3B2FI/AAAAAAAAB7I/-GtAtAGTYFo/s800/IMG_0229.JPG

http://lh3.ggpht.com/tann3r/SN0dIx56H5I/AAAAAAAAB7Q/hZBw96kHLoE/s800/IMG_0230.JPG

http://lh5.ggpht.com/tann3r/SN0dJJ7XynI/AAAAAAAAB7Y/DpfAj3m-oJg/s800/IMG_0231.JPG

http://lh3.ggpht.com/tann3r/SN0d8kzTJzI/AAAAAAAAB7k/uAbYSt7HCXo/s800/IMG_0232.JPG

I'm not sure exactly caused this, though i have ruled out a few things. At WOT the linkage hits the throttle stop before the TPS maxes out. Also at idle the linkage is on the stop before the TPS closes. So there is no binding between the spring loaded TPS and the linkage. At idle, however, the TPS is placing a load on the shaft, but if that were the culprit, I would expect the failure to occur closer to the TPS.

I'm not sure if it is a cause or a contributing factor, but I do have my W/I spraying both pre and post blower. The pre-blower nozzle was only added recently, only 1 track weekend on it, so I dont think it is to blame.

At the gas station when we were checking things out, a buddy jokingly asked if it was a BBK. Apparently they have a tendency to fail in this manner. I'm not sure if there is any credibility to this, but though it was funny given the circumstances.

I have the BTB apart if anyone wants any more pictures or anything. I've got a friend who happened to have a spare 65mm to get me back running until I can get another 75mm unit.

Thanks Tom for getting back to me this morning to verify the specification on the BTB. I'm looking at picking up an Accufab 75mm. I'm leaving Sunday for 4 weeks for work, so it'll be a while before i get it in and running. I'll update when i get back.

[Lee_The_CI]

I had the exact same faliure about 3 weeks ago with my BTB as well. Broke in the same place, right at that screw, Tom was nice enough to overnight me one.
It was not fun limping it home though...

[99mx5]

One procedure that will prevent this is adjusting the throttle pedal stop. This prevents pulling on the throttle linkage and forcing it against the stop. the pedal should hit the stop before the TB linkage hits its stop.

[Tom @ Fast Forward]

A little slack in the cable helps too. Funny, we never had a problem until the last couple weeks. Now we have had about 5. 4 were all from the same batch of TBs that I purchased and we sent them to BBK to check. We all figured it was a bad lot. This one is definitely NOT from that batch and broke the same way.

What I think happens is that the screw on the throttle plate loosens, the throttle plate shifts, the throttle plate sticks, you put your foot to the floor and, voila, the bar breaks. The screw is peened on the back side so it can't come out and go into the blower but, evidently, it will loosen. If you want to send it too me, BBK says they will rebuild it.

Each person, so far, says they feel a vibration before it happens and it also seems to stick. High idle or sticky to get off idle.