Hey all,

I have been on this site before searching for different things but this is my first time posting on here. Anyway, let me explain the issue I am having and see if anybody knows what might be going on.

About three weeks ago I purchased a used 2004 Rx-8 with 74k miles on it. For the first couple weeks the car ran ok except in hot weather, like 90+ degrees, the car would occasionally stall out after dropping from 4000+ rpms. I did some looking online and found multiple different things that may be the problem such as needed to clean the throttle body, clean the MAF, or maybe carbon build up in the engine.

So to try and remedy these I bought a fuel injection and engine cleaning fuel additive, an MAF cleaner, and a TB cleaner. My car has a Mazdaspeed Cold Air Intake on it which I took apart to clean the MAF and TB. I cleaned both and added the fuel additive to my gas (approx. 3/4 of a tank).

I put everything back together and waiting a little bit then started the car. It ran fine and idled at 850 rpms and I let it do so for about 5 to 10 minutes while I cleaned up. I then jumped in the car drove about 750 feet getting to like 25-30 mph in 1st and then when I pulled it out of gear the car stalled out.

Ever since then it has almost always stalled or dropped to like 300 rpms when I pull it out of gear. When the car doesnt stall out though, it hunts for idle and cannot stay idleing at 850 but jumps around alot. I also am getting a code from the engine light about a pre cat "too lean." Also when I was driving yesterday for about an hour the car had a sudden huge loss of power and refused to accelerate with the pedal to the floor. After it started to accelerate the engine light flashed a few times. I assume it misfired but I dont really know.

The problem has not really gotten any better but I have had multiple people (whom are fairly decent with regular cars) tell me it could be that the computer just needs to compensate for the now clean TB (since there was alot of buildup) or that the cat is bad or the O2 sensor is bad. Ive also heard that there could be a vacuum leak but I dont think so.

Also my uncle thought about resetting the computer and suggested unhooking the battery for a few minutes which we tried last night and the car still runs like crap.

I am new to the rotary world but have always thought the Rx-8 was a pretty sweet and unique car. Also, besides the cold air intake the car has racing sparkplug wires. These are the only mods to my knowledge and everything else is stock.

Any input is appreciated

 

Clean your ESS sensor. It's magnetic, so just wipe it off.

Little hard to get to, but that is exactly what will happen to my car if the ESS gets dirty. I clean that, the MAF, and the TB at tune-up time.



It is possible that it's just relearning the fuel trims, but that shouldn't take but one or two drive cycles. If you still can't maintain an idle, then clean that ESS.
Let me know if that fixes it please.

 

Agree with Mazurfer on his suggestions first. If that doesn't cure your ills then checking these out might be worthwhile:

https://www.rx8club.com/series-i-trouble-shooting-95/neutral-switch-133529/

https://www.rx8club.com/series-i-tech-garage-22/engine-code-p0850-engine-idle-hunt-problem-231084/

 

Thanks for the input. I cleaned off that sensor, which was really dirty by the way, and it seemed to help somewhat. I also had the fuel injectors cleaned out yesterday which also helped a whole lot. The car still is jumping around at idle, like between 750 to 1000 rpms mostly and sometimes dropping below 750 but catching itself.

One guy I spoke too said the gas smelled really lacquered and I only have about 1/15 of a tank left. Im hoping that some fresh gas will help aswell.

 

Did they physically remove the injectors to clean them?

If not ... my belief is that stuff is mostly just snake oil (just say'n)

Bad gas will cause issues for sure.

+1 with Mazsurfer
Now the neutral switch is interesting ... I've never read those posts, thanks for the link Voodoo

Other free items to check (depending on your mechanical skills)

- Clean maf
- Reset ESS learned memory with 20 brake stomp
- Check plugs
- Check air filter
- Check Throttle Body (clean)

And just to add another diagnosis thing to your list:
- IIRC a bad throttle body position sensor can cause Idle hunt

 

i would have said neutral switch having seen it alot here and dealt with it myself. but these guys have you covered as for what to check. good luck and let us know what you find.

 

Another thought.
When you took apart the CAI did you notice the screens?
If those are out of place, loose or missing you will have a weird idle as well.

Also check for open lines. uncapped nipples on the TB and UIM, things like that.

Major loss of power sounds like coils.

 

I had my buddies father take a look as my car today. He was a GMC master mechanic and he listened to the engine run and determined there was some kind of a "vacuum" leak and started spraying brake cleaner to find it.

As it turns out when I reinstalled the cold air intake into the rubber boot on the throttle body it wasnt pushed in all the way forward and was causing some kind either air leak or letting too much air in. Either way we adjusted it and now the car runs really smooth.

Also I did see those screens and they seemed proper when I put them back the last time but I adjusted them again. Anyway, thank you guys for your input and if it resumes to do the same thing as a later point I will know what else to check.

I also dont have a power loss anymore so I guess I can assume the coils to be ok.

 

Well........glad you got it fixed..........that's the main thing!

 

I went through a similar prob - with the "Hunting idle and occasional stall out."

Engine replacement = AUTHORIZED ! - RX8Club.com

Long story short....it was a tugged electrical line in one of the fuel pumps making the other one work harder and causing the hunting idle and occasional stall out.