I have an '04 Mazda RX-8 with 87500, I bought knowing it had issues and did extensive research before purchasing. No mods have been done except now I am straight piped for reasoning listed below.
I am going to start out by saying overall I love this car and have had an adventure with it since I bought it in September this last year. With that being said I have has a number of issues with this car that I cannot seem to fix, and by fixing preexisting issues seem to get worse.
Lets start with the things that I have replaced:
Spark Plugs - Twice
Wires - Twice
Coils - Once
Cat - 3 times (now straight piped)
Fuel Injectors - Once
Throttle Body Assembly - Once
MAF - Twice
O2 Sensors - Twice
All Recalls have been performed. Which took them a month to do...
Now with that being said I am sure that I have replaced other things that I cannot remember at this point.

When I first got the car I needed to replace the Cat, Plugs Ect. car ran great for 2-3 months, then I had an a significant loss of power, and replace the plugs and Cat again, and O2 Sensors. After replacing those the car ran great for another month or so. Then I had the Idle hunting issue then replace the MAF. That seemed to fix the issue. Until the next problem cropped up.

I initially had an issue with the Cat having a severe fuel dump collecting in it, removed and replaced injectors and cat. Car ran great for exactly three days. My cat clogged again and this time melted the O2 sensor that was located in the cat, my car had blown the honeycomb out and thus clogging my cat. Replaced everything bit by bit also took me about a month of not being able to drive my car, and only having weekends to work on it got my car up and running again. It ran very well for about two weeks, and now I am having an issue where only when the car is warm it will hunt for proper idle speed and eventually stall. Also when the car is running and I press on the accelerator slightly the RPMs will fall significantly and then rise.

Please help.. I really want to keep this car but I am getting to the point where I cannot keep doing this.

 

What intake do you have?

 

As far as I know it is completely stock has not been changed. At least I did not change it.

 

So it sounds like you're not getting an accurate or stable airflow measurements. Do you have an OBD reader or can you get one that connects to a smartphone? (they're about 15 bucks).

What you're looking for is long term and short term fuel trim data, airflow and AFR at idle. Once you have data, we can diagnose based on that. Do you have any malfunction codes?

 

I will be able to get accurate data tomorrow, I'll have access to an OBD2, where I can get more detailed information for you, I do not have any CELs.

 

Long term -10.15

Short 14.56

Not sure about the airflow or afr was not able to find that data.

I have reset my fuel trims in the past and nothing fixed the issue.
When I set the fuel pulse width for have the injectors fire at 3.2ms it idles completely fine and bring my fuel trims within 3% of each other.
my computer is not relearning itself and I have no clue why.

 

Fuel trims on a warm idle should be zero. Positive fuel trims mean you're ingesting unmetered air, so air that's not coming through the MAF. Start looking for a vacuum leak, a crack or unplgueed hose, somewhere in the intake and vacuum piping.

Er sorry, I misread. High negative LT fuel trim and positive ST fuel trim often points to an eccentric shaft position sensor problem. You can do the 20-time brake stomp procedure (look it up). Leave the injector pulse width at stock, there is nothing to be gained by playing with it. Some of the parts you replaced were probably not necessary.

 

I can bet most of them were not necessary either. I did that and now it will not stay running at all. It immediately dies as soon as I start it.

 

I also replaced the crankshaft position sensor as well

 

Believe it or not, not starting is progress. You changed something that produced a change in behavior, so we're getting warm. So yeah when you replace the sensor, you need to do the 20-time brake press thing, so it relearns the new sensor. It's in memory that disconnecting the battery won't clear.

I suppose pull the battery at the same time to clear the fuel trims, so everything is learning from fresh.

Does it normally have issues restarting while warm?
What did you replace the sensor with? Is it a Mazda original part?
No CELs at this point?

Since you've had the fuel injectors replaced, verify that they're plugged in correctly. Same for the wires and spark plugs, you'd be surprised how often people mix up which one goes to where. And yes, the engine will run, sort of, with them crosswired.

 

It starts but will not stay running. Dies as soon as the car starts. Unless I press on the throttle, and that was after the 20 brake "stomp". I replaced the injectors and plugs one at a time, plug for plug wire for wire. So I haven't crossed anything at least I shouldn't have. I haven't been able to find a reliable diagram for the plug wires. Same with a decent diagram for the vacuum hoses havent been able to find a reliable diagram to make sure that none of those hoses ended up crossed.

 

No CELs, previously it never had an issue starting while warm I have been getting progressively longer starts occasionally.
It is not a Mazda original part. Reason being is that they wanted $230 for a $50 part.
It will idle fine while it's cold but after it warms up it all goes to sh*t

 

Get data again as close to the point of dying.
Do you have an ignition coil tester to verify they're firing?

 

Long term sits at that point it will die or start to die when short term hits about -7.
I do have an induction timing light and they were all firing but I can check again and see if anything has changed in that regard.

 

I jucst checked to make sure all of my coils are firing they are indeed firing, I replaced the plugs about 3 weeks ago. The wires are NGK wires. They are all going to correct coils and plugs. I will post a video of what exactly it is doing. If I can figure out how that is.

 

Do you still have the original eccebtric shaft position sensor? Aftermarket sensors have been known to cause problems. If you can, try swapping the original back in and do the 20-timr brake press again. The symptoms so far tell me it's something with the sensor.

 

Seems like ESS doesn't fail often. Usually it just gets metal dust on it as it's magnetic, which can throw the reading off.

 

There was a thread maybe a month ago with similar symptoms: low ltft, high stft, unable to idle. I believe it went on for 3 pages and was solved by replacing the aftermarket ESS with a Mazda original one. You're right, they don't fail often, so the odds it needed to be replaced in the first place are pretty low.

 

It had the exact same issue with the mazda one in it. I was originally told it needed to be replaced, but here we are experiencing the same issue with one I got from intermotor. I even cleaned the other one to see if that would fox the issue and nothing. Is it possible the contact point needs to be cleaned?

 

Hmmmm. Yeah definitely examine the wiring and connector to the ESS. The thing is, if it was heavily damaged, the computer wouldn't be able to keep time and the coils wouldn't fire or fire intermittently. So I'm thinking that if it is the sensor, the actual problem is that the signal from it is noisy.

When you had the induction light on the coils, were they firing in a nice constant pattern?

One other thing I could recommend is pulling the spark plugs and examining the deposits on them. That'll tell if you the actual conditions in the engine. If they're black, you're rich. If 3 are clean and 1 is crusty, it's not wiring. That sort of thing. You can post pictures here so we can help read them.

 

When I had the induction light on the wires it was like a constant strobe on all 4 wires. I will check the condition of the plugs momentarily I will have pictures for you guys.
A new thing that has been happening now is my coolant light will come on and I am spraying coolant around my engine compartment.

 

 

I have also read that an aftermarket MAF will also cause the same issues that I'm having which I do have an aftermarket MAF.

 

This car has no camshaft

An aftermarket MAF could be it too. You can check via OBD what airflow value it reports. On a warm idle it should be a pretty steady 5-ish gram/second. About 13 g/sec on a cold idle at 1700rpm.

 

Thats what I thought... This is the information I was able to pull off of my OBD 2 and what my plugs look like.. Back
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