A mechanic told me that the Mazda FC Throttle Body is fragile – the steel throttle rod wears the opening in the aluminum body. This allows the throttle to jam wide open. The TB can’t be rebuilt and is dangerous. I’ve had the throttle jam open twice on my 91 TII. The first time Mazda replaced it and the second time I managed to find a new one.

What I want to know from you guys is if you’ve ever heard of this or if you know any horror stories. I’ve searched the archives and come across several ways the TB can get stuck at WOT such as –

floor mat interference (not my problem)
stuck throttle cable (not my problem)
problem with cruise control or cc cable
bound MOT rod
bolt stuck in TB control
dirty TB
my personal favorites -
razor blade stuck in throttle butterfly
gremlins

No one ever blamed the TB design. If there isn’t a basic design flaw, maybe I can clean up the TB with 64K miles and use it. If old TB’s are dangerous, we should all practice reaching for the ignition switch so that we can save our *** and engine when our toy goes WOT.

 

oh god not another one of these things.

you know, there is an ignition switch if that ever does happen, or better yet, pop it out of gear, and pull over.

sigh.

 

Yeah ... but the questions are does this happen a lot and is it a design problem?

 

never heard of that before, i think it's some mazda mechanic shenanigans

 

The best you can do is clean it and make sure nothing is in the way of the linkage. Your sure its not he linkage or pedal?

 

Wasn't the linkage or pedal for me. I think the cruise control is a possibility. If no one has ever heard of the sloppy hole theory, I've got o beleive the mechanic was snowing me. A lot of people make up stuff when they don't know or don't want to do something.

 

I've seen a few threads where it got stuck open, but I've never heard of a sloppy hole theory..... but I like the way that sounds.

 

my tb stuck open once after i let it sit for a while.

the solution u ask? WD40 on the arms that move the butterflies. It never happened again. and I have 110k on it.

All the stories I've heard of are from what you've already found, and i think your mechanic is just either messing with you or blowing smoke

 

Another reason why I am my own mechanic. I just can't trust anybody else.

 

All I can say is this is the first time I have heard a "sloppy hole theory" referred to in the context of RX7's. I think you might want to find a different mechanic.

 

I dont mind sloppy holes. Better than nothing

 

Never.

The throttle bodies can stick because of dirty external linkages. They can accumulate dirt and grunge, which gets stuck in the springs and actuators. Due to the double throttle design (and the vacuum operated tertiary throttles) the FC throttle body has more linkages then normal but they aren't really prone to jamming.

Also keep in mind that almost any car made in the last 30 years has an aluminum throttle body with a steel shaft. Sometimes bronze...

Most of the time the throttle body will stick if it's been cleaned or lubricated. They are designed to operate dry and if oiled, the oil will attract dirt. A simple spray down with brake cleaner generally frees it up. WD-40 is such a light oil that it evaporates quickly when the engine heats up so normally no harm is done.

 

Even if the pivot hole did get so hogged out that it became a problem, it would be quick work for a machine shop to mill it out and install a brass bushing.

 

or buy a used one from a forum member if yours is messed up. $30 make u hollla

 

Opps. Gross error. Never mind.

 

What you didnt see / hear is what your mechanic said to his friends after you left...

"guess what i got that a$$hole to believe!"

 

Probably, but the guy who said it didn't make any $$. He rebuilt carbs for a living. At the time, Mazda didn't stock any new ~1K TB's. I found a new one on the net for about $340 and had another mechanic install it.

 

Be glad you don't own an SR20DET...
Those things break TB's cause the throttle shafts snap in half.


-Ted

 

I have never seen a throttle body wear out to the point it would stick wide open. Even when covered in grease , grime and oxydation... Sounds to me like it was the linkage or the throttle cable or the gas pedal. I would say take a look up under your dash and make sure there is nothing impeding the pedal/linkage movement, like ghetto alarm wiring

post detailed pictures of said TB

 

<sarcasm>no, not a mechanic. that has to be the most honest trade i have ever heard of. </sarcasm>

i have never heard of the "sloppy hole theory" although i have seen a few. lol. i would lean towards cruise control on that one.

 

It's sitting in my garage and looks pretty good - untouched since I changed it. I'll post a picture as soon as I can get my act together.