Well, after screwing around last night for several hours, I managed to get the beast to run, albeit only on one rotor at a time.

I put everything together, hooked my downpipes into my ghetto-muffled-get-the-exhaust-outta-the-garage-so-I-can-test-fire-it system, filled it with coolant & oil, added a little two-stroke oil to the leading plug holes to lube the housings (first start without the OMP), and turned her over. Lotsa smoke and nastiness for about 15 minutes of cranking when finally...

She came to life....

But not in the usual way...

Reading 800 RPMs on the PFC with serious throttle-body-modulation (i.e. my foot on the gas) to keep it alive, the bitch moaned with a

phlaaaaap phlaaaaap phlaaaaap phlaaaap

...while belching loads of smoke. It seemed to only be running on the rear rotor, since I disconnected the #1 leading plug with no change. I moved the #2 leading plug wire to the #1 leading plug (same coil) and, well, it started running on the front rotor...

Pulled my plug wires off the leading coil, and sure enough, one of the bastards was broken off at the connector. Time for new plug wires, and maybe I'll have more than 1/2 a motor the next time I try to fire her up...

There's a slight possibility that I even broke the wire <while> I was pulling it off, so if anyone knows why the engine might run this way, please let me know.

I had -

good fuel pressure
no vacuum leaks
all sensors (map, etc) ok
clean plugs, etc

It really seemed like an ignition problem, so that's where I was leaning...

Went to sleep at 2:30 after deciding to call it quits (and not having any more plug wires).

 

might be flooded or bad spark plug?!

did you build this motor?

 

Eh, I'm fairly sure it was the bad plug wire, since either rotor would fire (but not both).

No, mazda built this motor

 

Do not put the plugs the wrong way for a long time - I probably destroyed my first engine due to detonation as a friend confused the spark plug wires...completely
Impressively, the car would start (abeit with FC sparks) and run well

 

Well, the T plugs are where they're supposed to be.

As I understand, the L coil is wasted spark so its position (1 or 2) is irrelevant.

 

correct

 

do you have any pics of your setup fully done? I haven't looked at your origianl thread about the project in a while but it was pretty interesting when it was always up top on the 3rd gen section.

 

oh, my the smoke

alright, so I replaced my plug wires and I'm still idling with a

phluuum phluuum phluuum phluuum

It sounds like something's missing (i.e. an ignition cycle).... swapped ECU's, same behavior. Fires right up on the first crank, just runs like crap. I have to keep the T/B open to keep it going.

Bad coil perhaps? What should I try?

 

Have you removed your airpump since you last started the car? With my airpump electrical connectors disconnected, the car has a very consistent drop in idle, it idles smoothly (without any throttle input) for maybe a second at a time, but drops by 200rpm or so at a very even interval (once per second maybe?), then goes back to idling fine for another second.

-s-

 

test for spark could be an open injector

 

No airpump. I am about to go and clear the plugs again.

 

Well, I'm making progress.

I let her warm up a bit even though she was running erratically. The idle was very rich around 600 RPMs with about 10mmHg vac with what seems like the ICV opening and closing trying to control the idle, then, at one point the fans kicked on and suddenly it idled perfectly around 800-900 rpms with smooth ignition throughout and 16-18 mmHg vac... then the fans shut off and it went back to its usual routine.

Intake manifold, ICV, 4x 850cc injectors, PFC, and that's about it. Ideas welcome.

 

I've heard its uncommon for an ignition coil to go bad. However, I've had the pleasure of having one go bad on me

The bad coil caused a lot black smoke out the exhaust. The smoke smelled HEAVILY of gas. The idle was extremely choppy, hard to start car sometimes. The car would drive initially (for maybe 2 weeks), but ran like ****. The car would bog really badly at mid rpms with plenty of black smoke. The car pop pop pop'ed a lot at idle.

Initally I thought it was the plugs/wires. Changed those to no effect. The plugs showed the car to be running extremely rich (no surprise). Finally I took it into a local Mazda dealer (the only one on Oahu that has experience with rx7s). They tested the car (not sure how they tested it, the guy knew of a method without actually having the car run, as my car would not start at this point). It turned out to be one of the coils. The car ran great afterwards.

Not sure if this is related to the problem with the coil, but they also had to clean the O2 sensor because the car would not come out of "limp home" mode after they replaced the coil.

Hope this helps

Ryan

 

Thanks, but I'm convinced it's computer related. After warming up, the car went from crappy to great and back again. Now it's cooled back down and I can't get it to start or run for more than 10-15 sec again. I'm stumped - I'm going to quit for tonight, unless anyone else has a novel idea. I've checked for vacuum leaks five times over. I've checked the MAP sensor - it's reading properly.

I'd be happier if it just didn't work at all... but why did it suddenly run great once the fans kicked on?

 

Alright, now that I have a chance to think about it...

First, thanks to everyone for your help and comments so far.

I'm fairly sure that the problem is not strictly mechanical. As I mentioned, there was a period of time that the car was under EL (per the PFC), I assume from the fans being on, during which it ran perfectly. I tried starting it with the rear defrost on (and the E/L indicator on), but no change.

I have repeatedly cleared the plugs, which makes it a bit easier to start; I also made sure the PFC was set for 850/850 and disabled the warm-up enrichment for the 30ish degC region, and that made it easier to get started.

Currently, there are no ancillary components other than the alternator, water pump, the idle control valve, four spark plugs, four injectors, and a fuel pressure regulator.

After cranking, the car will begin to fire, run crappily for about 20 seconds, and then die. When running, vacuum doesn't go under 10mmHg, although last night, for a minute or two (as I said before), the vacuum went down to a normal 16-18 mmHg and it idled great...

After turning the key off, the Idle Control Valve (or IACV, or ICS, or whatever mazda calls it) can be heard buzzing. Unplugging the connector stops the buzzing, but I don't think it closes the valve. Can they be stuck? When the car is limping along in idle there's a considerable amount of airflow going into the ICV port in the throttle body...

Should I remove the ICV and check to see if it is stuck open?

I also found this thread:

https://www.rx7club.com/3rd-generation-specific-1993-2002-16/car-starts-but-stalls-idle-189127/

Which describes the exact same problem. I sent him a PM.

 

And I just responded to your PM. But in order to give everyone some more info:

The problem I was having at the time of that thread was a leaky fuel injector (stock injectors). Actually, to be more accurate: one of the primaries was basically stuck open. The engine basically flooded itself out, unless I was somehow able to keep it running long enough to warm up. I replaced the injector with a stock replacement, and viola! Worked like a charm.


You said you replaced the wires, which didn't solve the problem. But have you tried replacing your coil with a known good one? It really sounds like an ignition related issue. Also have you made sure that you properly changed all the correct parameters in the PFC to account for all your modifications?

 

Thanks for the help, I just responded to your PM. I am going to try swapping in my old 550cc primaries tonight and see what happens... that just may take care of it.

IIRC some time ago I pressurized the fuel system and noticed that the pressure fell off pretty quickly after the fuel pump shut down... didn't think much of it. Perhaps I should have

 

haha. Good luck. Let us know how it turns out.

 

Also check all your grounding. I've seen cars run 100% better after changing out that grounding cable thats on the back corner of the uim. I run a 4gauge wire there and it made a HUGE difference in my idle. Could be that as you run larger injectors, ect you need more/better grounding points.

If you dont think thats the problem then (like already mentioned) I'd check injectors and the coil. Also, make sure the coil is connected well, sometimes those connectors where the harness plugs to the coil dont seat well. Might want to look at that if you havent already.

Did you remember that black spacer that goes under the primary rail?

 

I went over the grounding pretty thoroughly already but I will certainly check that out again, after I swap to known good primary injectors.

Already did!

Yep! The little guy sure is a PITA to get lined up prior to putting bolts in it, though!

 

Alright, I give up.

I swapped in the 550cc injectors (which I'm not entirely sure are good, anyway), and made appropriate PFC adjustments, checked the fuel pressure, etc, won't start.

Unflooded it about three times. I am thinking the excessive fuel/etc in the motor is left over from before. It's cold here so that's not helping starting either. It did fire for a few seconds and then died. This could have been residual fuel, or it could have been really running, who knows. Currently the plugs are out and I am just going to let it sit for a while.

Two things - does anyone know, on the 550cc injectors, are the pintles that stick out of the bottom of the injector supposed to be movable (like the 850cc's are?)... these 550's are very old and I'm worried they may have rusted/stuck/whatever.

Secondly, after the fuel pump is off and the engine is off, how much pressure should remain in the system and for how long? My pressure drops off pretty quickly, and is under 10 psi in about 20 seconds or so. Is that fuel leaking back through the pump, or might I have a leak somewhere?

I am exhausted and tired of screwing with this thing.

 

Yea, the pump leaks the fuel back into the tank. As long as you have 38-42psi of rail pressure at idle you should be ok as far as correct pressure and possible leaks are concerned. What is your actual fuel pressure at idle?

I think at this point its possible that this other set of injectors is bad but it seems more likely that you have an ignition problem rather than a 2nd set of bad injectors. Especially since earlier you said you pulled the first rotors plug wire off and it didnt make a difference in the way it ran.

I'd try swaping the coil.

Do you have an ignition amp like a HKS or MSD hooked up?

Have you checked the TPS and made sure its plugged in real good?

 

Found the problem. It's flooded as ****.

Although it's still not fixed, I have a leaking injector or primary rail (or leaking secondary injector or primary rail).

I don't think it's the secondaries, since the secondary rail is largely unmodified with the exception of being tapped for 1/8" NPT fittings.

I arrived at this conclusion after I pulled the plugs and cranked the engine with both leading plugs out. I was rewarded with clouds of fuel vapor and blackened liquid fuel goo flung all over the inside of my otherwise clean engine bay.

I decided to remove my downpipes; lo and behold I had LIQUID FUEL coming out of the downpipes! Yes, that's right, black, carbon-saturated gasoline pouring out of the exhaust. Sounds like I need to replace a rail/injectors.

So, I am currently looking for an unmodified primary rail & two 550cc stock injectors. I've got to start somewhere.

 

haha well sounds like you are set man good luck finding those parts .. peace

 

At first sounds like your vaccum hose from your boost sensor is off and should be connected to the intake plennum to the boost sensor. That would cause and sound like its missfiring and have to keep throttle open to about 3-4 rpm just to keep it going. But good luck if thats not it though.