zane9000

So last week I bought my first RX-7. I had never read much about rotary engines, but I am really liking all that I have been learning lately and my car is a blast to drive. I do have a few concerns though.
First, the engine tends to bog down a bit between 2k and 3k rpm. I wasn't sure what this was at first so I replaced all the plugs, wires, rotor, cap and checked that I have a strong spark on each plug. Since all that is good I am assuming that the issue is in the carb. The other day I was playing with the carb a bit and noticed that if I accelerate very slowly the car will just die completely around 2800 rpm. I know that I can probably fix this with a bit of trouble, but I think my plan is to buy a used carb and to a total tear down/ rebuild and convert to mechanical secondaries, then do a swap. That way I will learn more about the Nikki carbs inner workings and still have a running car in the mean time.

My second concern is the "Overheat Exhaust System" light comes on just about every time I drive it after about 10-15 minutes, then will shut off after a bit and not come on again till the next time I start it up. I figured I would drop my cat and see if I can unclog it, but what is the best way to do that? Should I just bang it against the ground until everything comes out? or maybe dump a solvent down in there? I have no idea... Sorry if this questions a a bit dumb, but I have never dealt with a car that needs emissions stuff. My main project car has been a 1973 Datsun and in California that means its smog exempt.... so keeping all my emissions equipment in good order may be a bit of a challenge for me :S

Thanks!

FirebirdSlayer666

iTrader: (3)

I would also replace the fuel filter and make sure the air filter is clean. A good way to see if the cat is clogged is to give it a good drive until the exhaust light comes on and pull over to see if the cat is glowing red at all. If it is then it's clogged. Welcome to the forums and post pictures of your RX

zane9000

I had meant to change the fuel filter also, just hadn't gotten around to it. Air filter is good. My car has a fuel filter right before the carb. Is there also one by the gas tank?

FirebirdSlayer666

iTrader: (3)

There may be

zane9000

Lol, thanks. Ill climb under there today.

zane9000

So last night the Overheat Exhaust System light came on again so I pulled over and got under the car to look at the cat. It was not glowing and the metal around it did not feel very warm. Does this mean I probably have a bad sensor or loose wire? I read that the sensor is located under the carpet under the seat. Which seat? Also is there an easy way to get under the carpet? I tried to pull it up but it didnt seem like it was going to happen very easily.

Thanks!

darkblaze

the exaust sensor is right behind the passanger seat close to the storage bends. i know this cause i ripped all the nasty A$$ carpet out. theres 1 wire for the sensor!

zane9000

Thanks. I will check it tonight and see if there is an issue. Any idea how the sensor works? Is it variable resistance or an on/off bi-metalic deal?

chiefmg

iTrader: (5)

The bogging might be due to your secondaries not opening. This would probably be caused by a faulty diaphragm in your actuating motor (little piece on the front left side of your carb as you face it). Long time ago mine went bad and it took me forever to find a dealer with a parts guy savvy enough to find it in the fiche. You should be able to check for this by removing the top of your air cleaner and having someone rev the engine. Looking down into the carb throats you should see the secondary butterflies open as well as extra fuel being squirted in from the accelerator pump (should be around 3,000 rpm IIRC). If the secondaries don't open you can move the actuating lever by hand while the engine is revved and see if that solves the problem.

The fuel filter should be located under the rear driver's side just ahead of the fuel tank. On an '81 it will be a white plastic cylinder with an inlet hose coming in one end and the outlet leaving the opposite end (this is for a factory filter).

FirebirdSlayer666

iTrader: (3)

Secondaries won't open while revving in neutral, they need to be under a vacuum load, or open then manually like you stated

zane9000

Actually, I was playing with them the other day and they do open while in neutral. I was just moving the main linkage by hand so I cant tell you what rpm they opened at, but they did. However they did not go all the way, so I am planing on rebuilding a carb and doing the mechanical linkage mod before installing.