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Jan. 13, 2011 7:49 p.m. unevolved HalfDork
I finally got the motor in my '85 RX-7 GS running, in the most basic sense of the word. This is not the original motor, although it is also from an '85 GS. The motor had over 120K miles on it when I got it, although I don't know the exact figure (dash was gone when I pulled the motor). I was merely promised it ran when the car was parted out (matter of weeks, not months/years). There was no stipulation on how well it would run, as it was only $150.

Here's my list of problems:
1. Surging Idle- Usually symptomatic of a vacuum leak, although I can't find one. Often caused by something else, though. Tach doesn't work either, although I just replaced the trailing coil.
2. Won't run without choke- It will idle for as long as I ask of it, but the moment I open the choke, it dies.
3. Water in the exhaust. LOTS of it.- Clouds of dark steam are coming out the exhaust filling up the garage, and puddles of black water are forming under an exhaust leak under the car. I tried an RX7Club recommended fix of Alumaseal (thread here: http://www.rx7club.com/showthread.php?t=750774) and that doesn't seem to be doing a lick of good.
1 and 2 could most likely be solved with a carburetor rebuild, but 3 worries me greatly. I'm afraid this motor is a paperweight. Is there anything I'm not seeing here, or not trying?
Jan. 13, 2011 7:53 p.m. MrJoshua SuperDork

Did you have the intake off? The o-rings leak letting coolant into the motor. Might be your issue.
Jan. 13, 2011 7:55 p.m. unevolved HalfDork

MrJoshua wrote:

Did you have the intake off? The o-rings leak letting coolant into the motor. Might be your issue.

I did, but I RTV'd quarters in there. Think that's worth checking on? This is just unholy amounts of water coming out of this engine.
Jan. 13, 2011 8:05 p.m. Curmudgeon SuperDork

I am assuming you are running antifreeze: Is it plain water leaking out or is there coolant in it? Plain water could be just accumulation in the exhaust, if it has coolant in it it's leaking from somewhere.

Before you go rebuilding the motor, see if the intake gasket is bad. (Mr Joshua beat me to this!) On 12A's there are two passages between the intake and engine which carry coolant. Leaking intake could explain both problems. Search rxclub, somewhere there's a how to on blocking the water passages with freeze plugs.

I had a carbed GS (my '82') do the same choke thing you describe, turned out to have just about every passage in the carb base plate clogged with goo because it had been sitting.

About the tach: have you confirmed the trailing ignition is actually working? Check for spark on that coil. No spark and no tach means probably the ignitor module on the dizzy is bad. If so and you have no spares, I have 4 extras for sale. Caution: when replacing those things, get real heat transfer grease (wheel bearing grease or white lithium will NOT do!) and coat the back of the module before installation.
Jan. 13, 2011 8:21 p.m. Toyman01 SuperDork

Steam and water in the exhaust is never a good sign. Is it a lot or just a small amount. Did it get better the longer it ran or stay the same. Like Jensenman said it could be just condensation. Your tach could have the same problem mine does. It doesn't work when it's cold. Once the heater starts warming the car is comes back to life. The carb probably needs a good cleaning. When I did mine I used the opportunity to strip most of the extra junk off of it as well as getting rid of the rats nest of vacuum lines under the hood. Good luck.
Jan. 13, 2011 8:30 p.m. unevolved HalfDork

I'm running plain water in the motor, and it's losing a lot through the exhaust, almost a cup a minute. I'm not a rotary expert, but that doesn't sound like most other coolant seal problems. The amount of steam always stayed consistent. I just got back from the store with some 20mm freeze plugs, Hylomar, and gasket material, and I'm gonna clean that sumbitch up and do it right.
Jan. 13, 2011 8:35 p.m. Tyler H Dork

On the bright side, if there was any carbon in there, it's gone now.
Jan. 13, 2011 9:59 p.m. unevolved HalfDork

Just pulled the IM, cleaned everything up, put in 20mm freeze plugs, cut a new gasket, and Hylomar'd both sides together.

Didn't change a damn thing. That wasn't it.
Jan. 13, 2011 10:30 p.m. amg_rx7 HalfDork

That is odd. I don't think a bad coolant seal could leak 1 cup a minute but I could be wrong.
Jan. 13, 2011 10:34 p.m. unevolved HalfDork

It's not leaking anywhere externally, it's all coming out the exhaust in one way or another. And it's a ton of smoke.

I may be in the market for a new project car here pretty soon. Anyone wanna trade for a clean RX7 shell with a great rebuild candidate?
Jan. 13, 2011 10:36 p.m. MrJoshua SuperDork

A megasquirted second gen 13b would really make that thing go!
Jan. 13, 2011 10:42 p.m. unevolved HalfDork

Definitely, make it go right into someone else's garage.

This is looking like the second AutoX season I have to sit out because of this car. Sure, rotaries can be reliable, but only if you start from scratch. There's no undoing previous owners' mistakes.