OK, just got this car, its an 85 GS, and my first rotary. I've owned many, many piston poppers, cars and motorcycles, and I've turned a lot of wrenches. Also I do mechanical engineering, so I'm semi-competent.

Seeing how there are many subject matter experts here, I wanted to ask for advice before I start.

I know that the car has a bad exhaust leak. I can smell it and hear it. The cat has a hole in it at the top, and is going to be replaced in the next couple of days.

Is a plugged cat enough to cause it to sputter and stumble at all speeds when the carb isn't in the secondaries? If I floor it and the secondaries open it doesn't miss as bad, if at all.

I've already replaced the plugs, cap, rotor and wires. The next thing that I want to do is replace the fuel filter and change the oil, and poke around to see if I can spot a leaking vacuum hose or something. I can hear a loud psssst type noise in the vicinity of the carb that I'm associating with the exhaust leak, like maybe the air pump line to the cat is blocked or something.

How much is a carb rebuild kit? That is next on my agenda if the new cat doesn't solve the problem. I think that I'd like to replace the majority all those miles of rubber hoses for the emissions and carby too in the event that they are leaking.

The AC doesn't work either, and that is another country heard from, but not a priority just yet. I was surprised that the cruise control and factory tape deck still work.

The gas hatch struts are shot, of course, and the driver's side door seal is disintegrating.

But the price of the car was right and its a blast to drive.

Any and all advice is greatly appreciated.

Thanks!

 

"sputter and stumble at all speeds when the carb isn't in the secondaries? "

Could this be the cause?
Maybe blocked jet causing primaries to run lean.
Clean out the carb.
Also "psssst type noise" could be air leak causing it to run lean.
Probably not the cat.

 

Okay, some ideas from an EFI guy.

1 - Change anything you can such as oil, fuel filter, check air filter, etc. (just to be sure)

2 - Stand over the engine and rev it to see if the "pssst" noise increases in intensity. If it does, find your vacuum leak. If it doesn't, ?

3 - Carb rebuild kits are pretty cheap (or so is my impression). Not sure where you can get them though, sorry.

4 - Has the car been sitting for awhile or anything? If it has, the gas tank may be corroded and in need of a cleaning. This could be affecting the fuel flow to the primaries (though I'm not sure why it wouldn't affect the secondaries).

Good luck, I'm sure someone on here will give you some better guidance than I ever could.

 

A clogged fuel filter will usually make the engine stumble when you mash the gas. If you haven't replaced it yet I'd do it anyway.

A clogged cat could cause these symptoms, but usually it would be bad performance throughout the car's power band, not just at low speeds. If you don't have to pass emissions I would check out the Bonez cat replacement pipe from Rotary Perfomance in Texas. http://www.rx7.com/cgi-local/1catalog.cgi?cat=4&part=2

Carb rebuild kits are around $60 from Mazdatrix. http://mazdatrix.com/c-3.htm

Victoria British sells a carb repair kit for $20. You can order a catalog on the web at http://victoriabritish.com/rx_cat_page.htm
I agree with Bruceman, this is likely to be your problem. You might find some usefull info at http://members.ij.net/mrmazda/btraps.html#CARBOVERHAUL

Ron

 

Not to disagree with my learned collegue, but instead of just replacing the cat with the Bonez pipe you may want to consider replacing the manifold, cats, and stock muffler wth the Racing Beat exhaust system (header, presilencer, and power pulse muffler) - you'll pick up at least 20 HP just from that bolt-on mod.

As to your immediate problem, odds are good it's the fuel filter.

 

I agree with that, but the replacement pipe is around $100, while the RB system is around $600 with shipping. If you can afford it definately go with the RB system. I have the dual pipe system on my GSLSE. Sounds great.

 

Thanks for all the input. Unfortunately the cat has already been purchased, and $$ is tight, so what I'm having put on is a direct replacement from Midas....I know, I know, but it does have a warrenty.....

I'm thinking that the pffffft noise is from the exhaust gas leaking out of the rusty, plugged cat. Not much seems to flow out of the tail pipes. I'm also wondering if it is from the air pump, like maybe the flow to the cat is blocked...doesn't it then go somewhere else? I need to get a manual.

Thanks for the link about rebuilding the carby. Is it really that difficult to remove? That writeup says to leave the body on the motor, and I'm visualizing me dropping a jet down the carb throat and into the motor while I'm trying to remove it.....

I would like to replace the rat's nest hoses with the silicon hoses, but how much of what sizes do I need?

I'm kicking myself today. I just found out that someone here at work had an 83 with a brand new rebuilt motor from the stealer...the tranny went out and the stealer quoted them $$$$ and so they sold the car for scrap!
I knew they were looking to sell it last month.

Once again, thanks for your help. I'm sure I'll have plenty more questions. (A/C doesn't work).

Strider

 

I know this may sound lame, but I kind of want to keep it stock. I don't have money for mods now, and if I did have the dosh, I'd drop it on my motorcycle. I just need good reliable transport for going to work. Economy is one of my criteria. If I really want to go fast I ride, and I don't think I could avoid tickets in the RX-7 like I do on my bike. (Extremely good brakes and small radar cross section on the bike, plus a good radar detector).

Strider

 

About replacing the rat's nest with hoses:

Speaking from my experience on 13B's, I assume it's similar. When you remove it, most of the lines take care of themselves so that there's actually very little vacuum line left. What is left (only a couple lines) can easily be replaced with 3.5mm silicone (rubber ok, silicone highly recommended) line. There's a ton of threads on this, just do a quick search (upper right corner of your screen). Good luck.

 

When disassembling the carb while on the engine, I stuff a shop rag into the carb ports tightly enough to prevent anything from falling in. Rebuild kits can be obtained from import parts houses, even NAPA offers a kit at approx. $25.00. The las one I purchased was from Vitory Imported Parts, Louisville, KY 502-239-8458, and it had a good exploeded diagram of the carb.

My Rx7 is an 83. I have replaced the fuel tank, pump, filter and fuel filler inlet pipe. I still have a no load miss that I am trying to resolve.

One of the guys thought the source of the problem may be in the emissions equip. I have not had time yet to experiment with this. You might go the the junk yard your friend sold his car to and see what they want for it?? May be worth it.

Be patient and you will get it right. But, they are not cheap transportation compared to more modern vehicles. If you want cheap, but not fun to drive, try an old Saturn, say 1992 or so. Have one with 125k that has cost almost nothing to operate.

Bes t regards,
THC

 

if you're not having the problem on the secondaries then it isn't anything to do with fuel starvation, bad tank, filter etc. if that were the case you'd be fine until you hit the secondaries. same with a clogged cat. it affects a car due to the exhaust gases not being able to escape through. this is, of course, compounded as rpm builds. i would go with a vacuum leak at this point. geta rebuild kit and a 5gallon bucket. fill the bucket with at least 1 gallon carb cleaner and the rest with gas. let all the metal parts soak for about a day, then scrub with brush or tooth brush. if possible, use compressed air to blow through the jets, etc. make sure to plug the intake manifold holes with paper towels as someone else said. also watch when you tearthe carb down as there are a couple of small ***** and rods in there. while you have the carb out,go ahead and replace all vacuum lines while the carb is out since its far easier to reach the carb base. this will fix any leaks since you'll have new gaskets and vacuum lines. it will also clear up any clogging in your primary jets. you will probably want to order new screens for the carb since they don't come in most local store rebuild kits. they are located in the end of the two runners off the main fuel line on top of the carb.

 

i have had all of those problems on my 85 gs. We just rebuilt the carb with a kit from a local mazda dealer, 85 dollars. i think it was worth the money, but beware, they dont come with the carb-to-manifold gasket. youll have to buy one of those seperatly. i guess you could leave the carb on the manifold when you take it apart, but i took it off and soaked it in carb cleaner for a few days. it looked alot better. and let me tell you, as big of a pain in the *** that was to get it back together right while it was off the car. if would have to be 10 times worse with it on the car.

 

OK, got the new cat put on today...runs much better. Starts better, much more power, and the missing isn't as pronounced. But the miss is still there. Its definately a vacuum leak. Sounds like someone letting air out of a tire. I think its somewhere right behind the carby under the air cleaner. I sprayed some WD-40 around, and when sprayed there the RPMs immediately smooth out and pick up. There is some type of valve there. I don't have a diagram in front of me, so I can't identify anything. It was on the passenger side behind the carb body. Anyway, I am going to get my hands on a rebuild kit tomorrow.

Problem is this: How do I purchase replacement hose if I don't know which is messed up? How do I know how much and what size hose to purchase if I want to replace it all with silicon hose? I see kits for hose, but I don't know what sizes I need....anyone done this can tell me what and how much I need to purchase?

Thanks!

 

i believe all the vacuum lines are 3.5mm. someone back me on this as i plan to do it here soon.