Hi,

I just got my first running RX-7 and it is a 1985 GSL-SE. I seems to run good, but the other day while driving it, it took off all on it's own. I had to shut the car off and coast to the next turn off. I tried to start it, and it went to redline again with no throttle input. Even while watching the throttle cable, and it not moving in the normal idle position, it went to redline. The third time I tried to start it, it ran properly, and I drove it around for a while with no further problems. Where should I look to try to figure out why it did this? Anyone else have this happen?

Thanks for your input,
Eric

 

i would manually operate the throttle under the hood, and if there is nothing obviously wrong like the throttle linkage stuck on a hose clamp or something, i'd probably clean out the throttle body

 

Sounds like a choke system or cruise control cable may be getting stuck.

 

Thanks for the suggestions. I am in the middle of some repairs on another car, but will either report back when I get the problem solved, or ask more questions when I can take a look again.

 

another idea: i would imagine there should be a throttle return spring somewhere on the throttle body. check to see if it's connected properly. i had a similar phenomenon happen to me several years ago and that's what it was.

 

sometimes the tb gets collected with crap n that will hold to plate open but will take a while to climb to red line(under load) but like these guys said check the spring and linkage to see iff its gettin caught. one instance on my friends se(will probably never happen to anyone else) he forgot to put the ground strap back on the tranny and the linkage became a new ground which welded the plates open, scary as ****!

 

This seems like an extremely common problem on Rotaries. I just read a thread not too long ago about the same issue. I don't know if it's just the throttle setup on the older engines or what, but it's not just you that this has happened to. And I'm not referring to welding the plates from a ground strap not being put back correctly, that would be some crazy stuff!

I had it happen to me as well, where on acceleration it stuck WOT on me and I had to shut it off and coast to a stop. It still did it on 3 start ups and on the 4th it was fine. I still, to this day, don't know what it was but it hasn't done it again. Mine though is a carbed 12a so I think it was my vacuum activated secondaries first time fully opening in the years the car had sat before I bought it. I must admit, it was quite a ride!

 

I haven't driven the car all that much since this has happened, just a couple of times, and it has not happened again. However, now it has a very eratic idle... swinging from 1200 to 350 or so and back again, and an occasional stalling out. The car had sat for over a year before I got it, so I probably need to get in there and get things cleaned up and checked out. It is very odd to me. I'll admit this is my first rotary car and I have a bunch to learn. Between this car and my 1989 Volvo 240, I'm learning diagnostics of quirky issues. All the other Mazdas we own have been pretty trouble free.

 

clean out the throttle body and the BAC valve, and then set the throttle position sensor. you're kind of right, this is one of the quirks of the car. the valve and throttle body get carboned up and require cleaning every decade or so

 

Water got in through the bin rust on the driver's side and corroded the cruise control unit.

Turn the cruise control off (button is near cig. lighter socket) and see if it goes away.

Yes, it's disconcerting when it happens. Yes, it's easiest to just do away with the cruise control.

 

I had this happen as well, its the tb butterflies, where the polls go through the tb spray it with some wd 40 inside and out. The metal is sticking, that should fix the problem. Worked for me perfect