Another starting problem! My 87 na starts excellently when cold, or when it's cooled off. But for the last two days, it starts on one rotor when hot, sometimes. If I shut it off, then restart a few times, it will run on two. It runs well, otherwise, steady idle, no hesitation, revs well...
I'm guessing fuel injector stuck, or a heat-short in a coil. Any experience with this?

 

Still no improvement on this. I have added MMO to the last two tanksful, but no improvement yet. I'm going to do spark plugs and plug wires this weekend (Mazdatrix willing), but the fact that it runs so well the first time I start it, but on one rotor when starting hot, then good again after a couple of hours sitting really has me stumped. Ignition? Coil? Fuel? I don't know!

 

try cleaning out your injectors.

 

sorry noob question, how can you tell if its only starting on one rotor?

 

lol.. if I let mine sit for a week or two, it likes to start on one rotor. sounds kinda lawnmowerish instead of rotary. it clears up for me in less than a minute though.

 

check compression

 

Believe me, you'll know it if it's running on one rotor! Sounds different, no power, shakes, etc....!
I spotted a code while it was running on one. One long pulse only, then repeats. My code list says O2 sensor, but I don't think that's it. It might mean CAS; I need to check which led is lighting to know for sure. CAS makes sense, I guess one side can go out due to heat. Anyone got a good shiney one for sale? SoCal area preferred!

 

My 86 GXL does this every once in a while, Its like it will half-flood a quick rev or a few seconds idling and it cleans right up thoguh

 

It definately was an O2 sensor code, which probably came up because raw gas is being fed to the exhaust manifold and downpipe. All I could do tonite was clean some connectors with contact cleaner (CAS, O2 sensor, grounds etc.), but I'm sure I'll have the problem again tomorrow.....

 

make sure your injector plugs are not loose.

 

I'll check those connectors next.

 

When this occurs overnight but not after a short shutdown/restart, it can indicate a coolant seal issue which is letting coolant seep in and puddle up in one of the 2 combustion chambers. Then when you start the engine the coolant gets splashed around and wets the sparkplug, and keeps it from firing until the heat burns the coolant off of the plug and it starts firing again. This would indicate a smaller, less advanced coolant seal leak, because the coolant leaks in slowly overnight, but not every time you shut it off and restart it.

IT could also be as simple as fouled/worn plugs that need to be changed.

Another good possibility is that you have a leaky fuel injector that follows the scenario listed above for coolant, but in this case gas is doing the flooding over a period of time.

I believe you are on he wrong track about the CAS and oxygen sensors...many an FC I have seen/rebuild runs perfectly with no o2 sensor whatsoever, except for a 1-2mpg difference on the highway. I was able to get 23mpg from my t2 on a trip recently without the factory o2 sensor...I had a wideband in it's place and the wideband had no narrowband output to hook up to the computer.

And CAS's themselves never go bad. At least I have never seen a truly bad one. The wiring may go bad, not the CAS. But if you are getting spark and fuel, then the CAS circuit is working properly.

 

RR, I hope you're right! I'll be putting in new plugs and wires this weekend, including going back to NGK wires and removing the two-year old Mallorys. The car starts very well when cold, after sitting overnite or for a couple of hours, so I think (hope!) the coolant seals are okay.
If there is no failure mode for the CAS where one side is out, then that would rule out the CAS.
The injectors have never been removed/cleaned, only gas treatment for them. I am hesitant to remove the UIM to get to them, but at this rate I will have to. I know it would help my mileage, which sits at about 15mpg around town with the air on.

 

Mazdatrix comes thru again! I'll be doing the plugs and wires this weekend, and try to get some compression readings while I'm at it...

 

This condition occurs even when I use a fuel-pump cut-off to stop the engine, so I can discount the leaky injector theory.
I am hoping that new plugs/wires and a coolant change will help. If it continues to show the same condition, is there any way to help a slow coolant seal leak without tearing open the engine?

 

When you use a fuel pump cutoff switch, the engine does not run the rails dry. There is still fuel in the rails, just not under pressure. Since injectors operate under pressure and won't really flow anything when not under pressure, the fuel pump cutoff kills the engine. But there is still fuel in the system, and a leaky injector can still...leak.

Although this is unlikely, so odds are you have a coolant seal issue. You can semi-check for that using these methods: http://www.rotaryresurrection.com/2n...l_failure.html

 

Mine alsways starts a little rough, sounds like it starts on every other chamber or something but smooths right out after a few seconds. It always done that and im not worried about it. Starts every time though, catches after the 3rd to 5th crank.

Its like, rump............rump............rump.......rump... ..rump....rump.rump, running.

 

Thanks RR, I'll be doing the test (#2 on your page) this morning when I do the spark plugs.

 

Well, the plugs came out dry after cranking it with the fuel off a few times. The rear rotor's plugs were fouled, black and sooty, but not wet. I've not had a problem starting the car after it sat overnight, so I guess this is not definative for my water seals. Cranking it with the plugs out sounded good, with even pulses, but I did not measure the compression.
Anyway, in went the new plugs and wires, and I changed the coolant.
Went for a drive and it ran well as usual, then I let it sit for five minutes. And it restarted on one rotor again, with an O2 sensor trouble light from raw gas. Problem not solved.
One thing: the trailing coil is too hot to touch after the car runs.
Sound like a bad water seal to you?

 

Sounds like a bad injector to me, fouling the plug temporarily with gas. If nothing else, swap both your rear injectors to the front, and then see if the problem moves to the other rotor.

 

Off comes the UIM, then?
May as well send the injectors out in a set for a cleaning. Where's the best left coast expert who can do a quick turnaround for me? I'd overnite them if I can.
Never pulled the UIM before. Do I need a gasket, or a gasket kit? O-rings for the injectors?
I need to solve this, I've been finding myself looking at Mustang and PT Cruiser ads....but I saw one local RX-8 around $21.5 new

 

You could start with just the secondaries if you want to do some quick troubleshooting...but if a primary is the issue, then yes the UIM will have to come off. It is not terribly hard to do, but you should plan to do gaskets, vacuum hoses, etc.

The first few steps of this can get you there:

http://www.rotaryresurrection.com/2n..._teardown.html

If it were me I would pull the LIM as well and clean/overhaul my 6 port rotating assemblies, and do all new intake gaskets from the block up. If you take your time and replace every rubber and paper part on the top end of the engine you might be surprised how much nicer it runs.

The new mustangs look like dogshit when they are stock/base, but the ones with bodykits and trim on them actually look pretty sick. Even the previous generation mustangs did not look bad at all when fixed up, and I have never been a ford guy.

But a PT Snoozer?

21.5 is a pretty good price for a new '8. The car drives well, handling is on par with an FD. Think of it as a modern FD in a nonturbo/cheaper/more reliable format. They still have their share of issues though.

 

Yikes!
The Mustang reminds me of my '66 289 coupe. Fun car. And I saw PT's in the paper for $12.5K today.

I guess I'll order a PD and some gaskets and check into the injector service. If I rent a PT for a week, that might just cure me!

 

How's RC Engineering in Torrance? I remember Russ Collins racing some fast motorcycles back a ways...Honda fours, I think...
People have posted good things about them.

 

RC is who I use for service. Not accounting for shipping, they usually turn injectors around in 48 business hours.