low RPM bucking
 

When I'm just driving around town 25-45 mph, the engine bucks a lot. I get the same thing while slowing down on the freeway also. Is this a carb adjustment ?('85 base model RX7)

Good question. I'd like to know about this one as well, though mine only does it below 2k rpm and only in first or second.

It could be a carb adjustment, although the symptoms sound more like a bad motor or transmission mount. Generally, if the air adjust screw is misadjusted, the motor kind of "surges" rather than bucking like you mentioned.

After looking at some of the threads on the web site, I believe its the idle mixture screw. The car only has 81k and the trans is very tight.
There is a metal cap over the idle mix screw, how do you get this off(its very hard to see whats holding it on and the manual shows it in a different place!

what type of bucking does it feel like. Is it a total loss of power, or just a surging where theres lotsa power, little power lotsa power. I would say its the engine mounts and suggest getting new engine mounts, or a torque brace. Just my .02 thou

Its the around or under 2k studder I've now read about in othet threads. The engine mounts are in great shape, the car only has 81k on it (the engine is so clean you could eat off of it.)
Anyone know how to get the metal cap off of the mixture screw without breaking anything?

mine did it when the engine was about to pop, due to too low of vacume
just an idea
BTW bouis you sure you dont knwo anyone with a 12a?

Re: low RPM bucking
 

If it's occuring when coasting between about 1500 and 2500, the "problem" is that you have a rotary.

The shutter valve is supposed to alleviate this, but it's possible that yours is not functioning for whatever reason. IN any event it's not perfect, and so you still get bucking.

Note that the bucking is intake vacuum related. And as you make the ports bigger, the bucking threshold gets lower until it bucks at *idle*. Brap brap brap brap...

Sorry wwilliam, I don't know of any 12a's around. Well, none with less than 190k miles anyway.

We'll have to put off that test ride too, as I still have some issues to work out. I'd tell you more but I'm waiting to see what CP Racing will do.

pm me about that 190k one, i might need some spare parts

How do you get the metal cap off of the idle mixture screw without breaking something? Anyone?

dremel?
thre is a special tool tht gets around it, the haynes manuel tells about it

I don't know about the metal cap, but I have read that a torque brace will solve this "bucking". Its just something a rotary does. Nature of the beast it seems (or something like that).

Where can I get a torque brace? There seems to be plenty available for FCs and FDs but I seldom come across one for the FB.

I've owned four RX-7's that all did this, despite changing bushes and playing with the coasting valve. Possibly related to having removed all the emissions gear, but I'm not too sure having never driven a RX with any emissions still on it. I just put it down to the lack of torque & engine braking inherent in the rotary design when deaccelerating. Meh, you learn to drive around it pretty quick.

Any engine will do that if you get the RPMs low enough.

www.racingbeat.com They sell torque braces, they're pretty cheap too.