Rough start and white smoke, but no coolant smell in exhaust
 

There are a lot of threads here about white smoke, but most of them also report a coolant smell in the exhaust, indicating a failing water seal.

I've got white smoke for 30 seconds or so on a cold start, but zero coolant smell from the exhaust, and it starts up fine while cold. It does idle roughly for those 30 seconds, and then it's fine after that. There IS a coolant leak somewhere. I can smell coolant in the engine bay after running it for a while, and the coolant level is dropping. But no coolant smell in the exhaust. It needs additional coolant daily.

This could be a separate issue, but in addition to the above, it has trouble starting when it's hot. To get it to start when it's hot, I crank it for about 2 seconds, then release the ignition. I repeat that 2 or 3 times, and then it fires right up. Then it has a rough idle for 5-10 seconds.

Once it's started up and running smoothly, there's no loss of power or any other problems while driving. No problems idling at stoplights. All the problems are right at startup.

I just bought it a few days ago, and the previous owner just recently changed the coils and wires. I changed the spark plugs 2 days ago, and when I did, the rear 2 plugs came out with black, sticky goo on them. Probably not coincidentally, I'm getting a flashing CEL (misfire), and the code indicates it's the rear rotor.

I'm working my way through the troubleshooting tips in the misfire and rough idle threads. In the meanwhile, I was wondering if anyone had any ideas about what could be going on.

I had an RX-8 before, but I had to sell it 9 years ago to move overseas. I'm back now, and really glad to have an RX-8 again, even if it does have a few problems ;)

Sort of an obvious question but did have a compression test done before buying? Those symptoms point to a likely new engine in your future, regardless of where specifically the leak is.

Still, one thing to consider is a stuck injector in the rear rotor. Black goo means excess of gas or oil. If oil, Wwe are back to new engine time. If gas, you might be running silly rich in that rotor

I almost did a compression test before I bought it, but decided not to after I test drove it. Other than startup, it drives great with no loss of power, so I kind of just crossed my fingers and hoped for the best. Also, I really want to try my hand at a rebuild, so I wasn't super worried about the engine possibly being on its way out. The car is on its second engine, and the "new" one has 60k miles on it.

Thanks for the suggestion about the injector. If there's that much oil I would probably be seeing blue-ish smoke, right? If it's a stuck injector, do you think I need to take it out to fix it? On the other hand, would I be getting a CEL with a code that indicates it's running too rich? The only code I'm getting is P0302 (misfire).

Correct, oil smoke is bluish. White smoke that doesn't smell like coolant could be simple condensation, or it could be running pig rich, which is why I thought the injectors might be involved. How much smoke are we talking?

The other thing is, if the previous owner did not actually change all the coils, or changed them with faulty ones, you'd have the same symptoms. Try to swap rear rotor coils to the front and see if the misfire travels with the coils. OR if you're handy with electronics, pull the coils out and check that they in resistance spec. Here's a guide:


For your coolant smell, if it smells under the hood, see where it's leaking. One known issue is broken overflow bottles, so check around and under there for green deposits (assuming the previous owner used proper Mazda coolant). Check under the engine as well. It's got to be somewhere.

The smoke isn't very thick, but it does seem thicker than condensation would be. The weather's also still pretty hot here in San Antonio. As it's idling a little rough during a cold start, it's a light, steady stream, and then every few seconds there's a stronger puff from the rough idle and it blows a ring of smoke. Reminds me of Gandalf.

Great advice about the coils. I'll test their resistance, and may switch them as well just in case.

Looks like there is a little coolant under the reservoir, but maybe I splashed a little when I topped it up. I'll top it up again and make sure it's all clean, then inspect again as it gets low.

Thanks!

If it's smoking white it could be coolant or oil, I have seen both emit white smoke on my own car. But you need to start at square one and troubleshoot.

The coolant reservoir definitely has a leak. Ordered a replacement. Still need to check those coils.