i know it sounds bad and yes i’m looking into a rebuild for a coolant seal but i wanted some more insight. car has a rough cold start with smoke but when warm it more or less perfect besides running pig rich on stock ecu that i’ve been trying to figure out for a week also.

 

Check your vacuum, map sensor, 02 sensor. Could be a stuck or leaking injector, stuck side or corner seal.

 

It could be a few different things. Its not always a bad coolant seal. Similar symptoms exist with various issues.

It could be an injector issue, an issue with one of the seals on the rotors, a coolant seal of course or a number of other things. You just have to run through the troubleshooting process to rule things out.

If you're looking for help then being less vague with what's going on helps us help you. Giving information about the car, the set up, what mods or maintenance things you've done recently, the last time the car was running fine, what happened between it being fine to not, PICTURES.....

The more information you give us the more useful the community is. You'd be surprised what things were noticed from pictures that weren't even relevant until it was seen..

to summarize, your question here is basically "my car is doing something its not supposed to. What do you guys think it is".... theres nothing we can with that.

 

if its rich, that can lead to the rough start/one rotor starts, mine would do that if i started it and didn't warm it up all the way on the stock ecu

 

Since it's running way too rich, I agree with the above that it's more likely that issue that's causing the 1-rotor starts from being flooded.

If you're not losing coolant, it's not likely a coolant seal issue.

 

Boy there are a lot of things it can be. The oem ecu is really temperamental. What do the plugs look like?

 

i did notice some black carbon build-up on the leading plugs. thinking possible coolant sensor making the ecu run it too rich and I'm flooding

 

yeah, no problems overheating or topping off the system, just the rough cold start. thinking maybe the coolant sensor is faulty and I heard it would make the ecu run rich

 

car is fully stock with an axle back, high mileage now with 102k. changed the o2 sensor and spark plugs and no luck on that. bled the whole coolant system and seems to run better when warm but still having 1 rotor cold starts until i give it a slight rev

 

any error codes?

 

Mine does this same thing. Takes about 3 tries to start it with some accelerator help and then it slowly chugs to life. Tons of fuel smoke at start up. Idles rough as hell when cold. Once warmed up, she's fine; stable idle at 980 to 1000 rpm. No clue as how to fix. I just deal with it.

 

Guessing, but it sounds like a leaky fuel injector loading the intake with fuel after shutdown.

 

anything i can run through the system or is it best to just take them out and get them rebuilt and cleaned ?

 

It's worth running some injector cleaner through, doesn't cost much and it's easy to do. You will want to get on the secondary injectors as much as you can when you are running that tank through so they get hit with the cleaner as well.

Dale

 

so more or less just let it open up while on this tank with cleaner

 

sounds like fun haha, hopefully this works. if not i’ll be pulling the injectors in hope of that fixing it all!

 

If you suspect a sticking injector(s) I don’t think it hurts to run a bit higher dose of a good injector cleaner…or repeat it a tank or two. I like the BG stuff the best or Techron. It doesn’t sound all that serious to me. Personally I would definitely try the cleaners before deep-diving to pull injectors.

Unless you’re pumping out steam with a distinctive sweet smell to it on cold start…your coolant seals are probably fine.

What’s the ambient temp btw when you have these lumpy starts? There’s also a fuel temp sensor but not certain of symptoms from a bad one.

 

just started it after running half tank of cleaner and still one rotor start with a lot of distinct BLUE smoke. cleared up after a little rev

 

in california so morning before class is high 60’s low (fahrenheit)

 

Aw man,

I had the exact symptoms as RotaryRTK, and it sounds like the OP is having the same problem. It ended up being an Oring leaking from my injector, and I believe the injector itself was leaking in the intake; this was part of Mazda's recall for FDs catching on fire. (If I'm not mistaken) I just dealt with the problem, which eventually worsened over the months. Finally, the leak got so bad I had raw fuel dripping on my floor, so be cautious of this problem.

I would do a fuel pressure test to see if it holds pressure because when I did a pressure test; it couldn't keep above 20PSI; the average is 32-34 psi at idle. My injectors were leaking inside the intake since the car would idle rough and smokey during a cold start and eventually turn normal. Also, one rotor did this, like yours.

It's a tough job to replace the injectors. I don't recommend rebuilding them because the shop that rebuilt mine destroyed them by crushing the plastic filter screens to the primary's, which you can't buy separately.

I recommend buying new injectors, which come with new Orings. This is what fixed my problem. On top of that, I would replace the primary and secondary grommets and the primary and secondary injector diffusers since it's a big job to get to them if you still have the rat's nest. This also opens up a can of worms because you have to remove the rat's nest to get to the primary injectors.. so yeah. There's that.

Part's list that fixed my issue:
Rx7 Primary Fuel Injector (N3A1-13-250)
Rx7 Secondary Fuel Injector (N3A2-13-250)
Lower Primary Fuel Injector Grommet (N3A1-13-257)
Lower Secondary Fuel Injector Grommet (NF01-13-257A)
Primary Fuel Injector Diffuser (N3A2-13-C61)
Secondary Fuel Injector Diffuser (N3A1-13-C60)

 

super grateful for this response. going to grab a pressure tester and see what happens. i’d be happier with injectors then a coolant seal.

 

42 psi before starting with f/p and grnd jumped in diagnostic box, and 33 at idle. starting to think it’s something electrical. car ran solid though. barely a hiccup on start

 

Did you monitor the FP after shut-down with the pump off? That should tell you if an injector is leaking or not. It one or more are leaking the FP will drop off fairly quickly after shut-down.

 

FP is 30 psi after more or less 20 minutes

 

I've got to swap my plugs and wires this weekend, so I will run a can of injector cleaner through and see if that helps clear the problem. I have a FP gauge in the engine bay and it's super slow to drop to 0 after shut down. I will pop the hood when idling to see if it gets above 30psi. I do know that if I run her consecutive days, there isn't as much smoke and she starts on the first try. Everything on my car is 15 plus years old, so I'm slowly replacing everything with new.