ProfessorRat

Hello,

Sorry for posting this in the New Members forum; I normally don't do anything more than lurk and learn, so I haven't met my 10 post quota for proper use of the forums.

In August of 2020, I acquired a brand new (to me), abandoned 2009 RX8 Sport. It had some front end damage, but beyond that was mechanically sound. I did a quick oil change in the parking lot, swapped in a new battery, and drove it home.
Since then, I have done two additional oil changes, replaced the spark plugs, coils, air filter, and flushed the coolant system. No check engine lights, and the coolant level detector seems to work intermittently. Started driving it regularly, with a red line every drive.
Shortly after I came back from deployment in December, I borrowed a compression tester. All values for each rotor face were between 7.5-8.0, with the exception of one 7.3 in the mix.
So, to this point, I assumed the engine was in fair working order. I started buying some parts to put on it; a new exhaust, an exhaust header, etc. Even bought a body kit, because I couldn't find a replacement stock front bumper that would ship out to this tiny little pacific island of mine.

Everything was going well until yesterday, on the way from from work.
I was not driving the car particularly hard, but figured I should red line it once before pulling into town, so I don't get a ticket. It revved fine, then about 2 minutes later, I started having significant acceleration issues. The engine was bogging down pretty significantly at any RPM. Coming to a stop at the light, it idled fine. I took off from the light, and I was unable to maintain above 3k RPM. I continued driving a little bit to get to a parking lot and get off the road. As I started to pull off the road, my temperature started climbing and I immediately shut the car off.
To this point, there are no check engine lights, no warning lights whatsoever.

I pushed the car into the parking lot, and let it cool for a bit. I checked the level in the coolant reservoir, and while not empty, was not on the full line, so I topped it off. Oil is mid dipstick.
After waiting for about half an hour, started the car, idled perfect, still no check engine light, temperatures are normal.
Got back on the road, and about 5 minutes of driving, same symptoms as before. Shut it down and pulled over again.

I had places to be, so I hiked home and left the car for about 5 hours. Came back, and drove it home. Once it got up to temp, smelled anti freeze and the coolant level warning light came in. Thankfully this time I was uphill from my house, and coasted it back home with the car off.

It is now the next day. Still not throwing any check engine light. OBDII scanner doesn't report any misfire conditions. I do not have any visible oil in my coolant reservoir, nor to I have any blowby into the reservoir when the engine is running. It runs and revvs fine in the driveway, no abnormal noises. Checked the cat by visual inspection after getting it up to temp, but I don't think they get too hot unless under loading. It appeared normal.

OBDII Fuel pressure indications also seemed to be normal.

A leak has developed in the coolant system that I'm currently trying to find. Definitely not going to be driving it until I have that fixed.

My questions are:

What could have caused the loss of power issue?
My thoughts tend towards a fuel pump or catalytic converter problem, but I'm honestly kind of stumped.

I've seen posts with somewhat similar issues to what I've had, but they all seem to present themselves gradually. The power cut was all at once, and seemed to go away after I let it sit for a while, only to reappear.




I'm a little bit tired of buying parts for my cars, only to have them break in some new way before the parts arrive.

Loki

iTrader: (1)

Does it specifically not go over 3k rpm? Idles fine? That sounds like limp mode. There are relatively few potential causes: failed coolant temperature sensor or failed OMP control. On S1's its usually the 2nd and usually easily fixable by cleaning and reinstalling the OMP connection. On an S2 I'm not sure, but follow similar logic. I suspect that when you find your coolant leak you'll find clues to the cause.

Fuel pumps don't usually suddenly underdeliver fuel, they die and stall the car. It's probably not the cat either, you would have misfires and power loss at high rpm, but not low down. But it doesn't hurt to check the cat on any new to you 8.

ProfessorRat

No, it wasn't specific to 3k. Once it started getting hot, could barely keep it above idle, before shutting it off. I really hope the engine isn't damaged. I'll have to bring a case of beer to my buddy to borrow his compression tester again. Right now, though, if I go fill it up with water and run it, I can rev all I want, so it isn't stuck in any sort of limp mode.

Coolant leak turned out to be from the top of the radiator, seemingly on a seam between the fins and the plastic bit. Just bought a new radiator and hose set that will arrive in the next few weeks.
When I started it after throwing it on stands, I got a code for the MAF sensor and and a P2070 code. Weird that they didn't show up before.
This little snafu is rapidly eating into the cash I had saved up for bodywork and paint!

CaymanRotary

Compression test. Sounds like the engine is at end of life. Probably overheated from the leak. The cooling system is pressurized, so a leak is a big problem that can lead to overheating, which leads to seal failure.