TannerRich

Okay like I said just bought my RX-8 it runs and idles but is stuck in limp mode. I attempted to run a compression test myself and I'm not sure if I did it right but I'm pretty sure I need a rebuild. Then today I was checking the omp and the oil lines are very brittle and look like the might be dry. I looked at the bottom of it and saw this. Probably need a new one I'm guessing lol

MincVinyl

Can you give more details towards the condition of the engine?
Miles?
Codes?
Wont go over 5-6k rpm?
Wont hot start?
dies at idle when hot?
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If the omp is toast might want to read up on premixing to save the engine. The 4 oil lines to the injectors will become VERY brittle over time which is usual since they are in a high temp area and will break easily.
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Unless you get an actual rotary compression tester it is hard to really go off of whatever compression numbers you get. This is due to how compression increases with rpm, a tester adjusts values to 250rpm for comparable results. However if you are not having hot start issues, flooding issues, or smoke of any sort, the engine might be good for a while.

CaymanRotary

Would concur with the above. Don't be so quick to pull the engine. Make sure its damaged before putting the effort into rebuilding. Many times, it's a different issue than low compression that can cause engine issues.

TannerRich

Forgot to add miles. It has 160k it had an engine rebuild at 80k and thats another reason why I assumed it needed a rebuild

TannerRich

It has been sitting for around a year, when I got it the idle was rough it would sit around 1000 rpm then sound like it was going to stall. After I tried to run a compression test (with a cylinder compression tester) it now idles better with a little vibration. After it warms up it won't start again until it cools some. When it first starts it will rev but after a few seconds it won't go past about 4000rpm. The compression test I tried to do read 60 psi in the rear rotor and 70 in the front all 3 sides of both rotors pulsed at the same psi, but I have no idea what rpm it was turning at. From what the guy told me it was running when it was put away before last winter. I've had it since Friday, a week before that I didn't even know what a rotary engine was but I've been reading a lot on here and I really like the car and am going to try to do all the work myself. I'm pretty good mechanically so I shouldn't have much trouble it's a fun project and a learning experience, so any help is greatly appreciated.

TannerRich

It has been sitting for around a year, when I got it the idle was rough it would sit around 1000 rpm then sound like it was going to stall. After I tried to run a compression test (with a cylinder compression tester) it now idles better with a little vibration. After it warms up it won't start again until it cools some. When it first starts it will rev but after a few seconds it won't go past about 4000rpm. The compression test I tried to do read 60 psi in the rear rotor and 70 in the front all 3 sides of both rotors pulsed at the same psi, but I have no idea what rpm it was turning at. From what the guy told me it was running when it was put away before last winter. I've had it since Friday, a week before that I didn't even know what a rotary engine was but I've been reading a lot on here and I really like the car and am going to try to do all the work myself. I'm pretty good mechanically so I shouldn't have much trouble it's a fun project and a learning experience, so any help is greatly appreciated. I tried posting this with the pictures of the codes a couple times so sorry if it posts a bunch of copy's of the same thing

TannerRich

P0442 evaporative emission system leak detected (small leak)P0113 intake air temperature sensor 1 circuit highP0103 mass or volume air flow a circuit high

TannerRich

P0442 evaporative emission system leak detected (small leak)P0113 intake air temperature sensor 1 circuit highP0103 mass or volume air flow a circuit high

Loki

iTrader: (1)

Before you go and rebuild the engine, let's fix the immediate problems. The engine might be on its way out, but you don't want to fix it, put it back in, and only then start dealing with problems that aren't the engine. It'll be much harder to diagnose anything after you've taken it all apart.

Also I'd strongly suggest not trying to fix your engine. That's not how this stuff works. You want an engine built out of good, reusable parts of other engines. Chances are your engine doesn't have a complete set of good parts now, and you need to go buy them which baloons the expense. You're much better off buying a known good engine from a known good rebuilder (Pineapple Racing, Pettit, Rotary Resurrection, Mazda dealer, etc.)

P0442 sounds like a loose gas cap or disconnected vacuum hose to the EVAP system. Easy fixes.
P0103 & P0113 sound like your MAF is not connected. The temperature sensors is in the MAF, they're the same plug.

Not revving over 4000 is your OMP, almost guaranteed. The crack you see might be a sign someone has had it off the car and didn't bolt it back in properly (it looks loose, not cracked), which might also be a sign they didn't know how to align it properly and now the computer can't make heads or tails of what the OMP is doing. Reassembling the OMP requires alignment. Relatively easy fix, it's well documented here as many people overlook that detail when messing with their OMP.

BigCajun

iTrader: (1)

+1^

Idk how much research you've done.
Better too much than not enough.

I would recommend reading Shadycrew's amusing but relevant rebuilding thread.

https://www.rx8club.com/series-i-tec...engine-231883/

Then read the Rebuilders thread, there are several other threads linked in it that could be helpful to you.

https://www.rx8club.com/rx-8-discuss...ilders-265177/

MincVinyl

So if the car is having those hot start issues, it is 90% going to be failing compression. Depending on what was used in the original rebuild, you could be looking at replacing rotors as well as the usual housings/seals all around (go with mazda oem for side/corner/apex)
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Imo while the engine still starts to a degree it may be worth it to try to fix as many of these other issues you are listing so you have a solid car ready for a new engine. The codes are possibly why it wants to die at idle, yes low compression will inevitably cause bad idle but that only happens at the very end of an engines life after already suffering with hot start issues. Mine couldn't idle after about 3000 miles after hot start issues started (a night of spirited driving was the last nail in the coffin).
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After your engine codes are solved
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If your starter can spin the engine at 300+rpm when starting, that means your battery/starter are in a decent position. If you are getting less than 200rpm it could definitely be hindering compression due to spinning to slowly. Many people end up upgrading to a more powerful starter+ high CCA battery.

Ignition coils/plugs could help idle for sure. People tend to go to an LS coil kit. Maybe take a look at the crank position sensor and clean it off.

Issues climbing in rpm can be signs of a bad fuel pump, and at that mileage it wouldn't surprise me that it is dying as well. (check your intake for vacuum leaks or maf issues first to see if those clear up idle+rpm) other than that I'd point my finger at the fuel injectors/gas.

TannerRich

Okay so just want to let everyone know that I am constantly reading threads and learning all I can about this car and I realize I may have bitten off more than I can chew, BUT I am willing to put the time and effort into doing whatever it takes to get this thing on the road even if that doesn't happen until next summer. I'm very interested in the rotary engine because it's different and it gets a lot of hate because of all the maintenance it requires and that just makes me like it more. Again I appreciate the help and now at least I know where to start because I am a little overwhelmed, I'm going to start collecting the parts and tools start with the small stuff you guys are talking about and work my way up. I'm probably getting a settlement next year so worst case scenario I end up having it rebuilt by a professional then

MincVinyl

https://www.rx8club.com/new-member-f...rx-8-a-233937/

This is a good read through when you have time, helped me a bunch when it came time to choosing things to get stock or upgrade while i'm at it.

I'd definitely say that the biggest issue with rotaries is the knowledge gap you have to first cross. Sucks that due to many people selling neglected cars that new rx8 owners end up going through a nightmare initially. I got both mine for under $2000....they were not in great condition by any means, but I built it up to a great car. Trying to get a third right now that is a rust free shinka edition.

CaymanRotary

Same, 3 of the 5 RX8's I l've got were under $2000 to purchase. That being said, the best cars always arrive on tow trucks.

TannerRich

I got the car for 800 plus 50 bucks to borrow a friend's trailer, and everything is in really good shape accept the front tires and whatever is going on with the engine so I really can't complain, if it turns out the engine does need rebuilt I may just shop around for another one and just replace it, I've looked a little but all I've seen comes with a transmission. This is a 6 speed btw I don't think I've specified

MincVinyl

If you are not planning on rebuilding yourself, make sure you really do research on builders. Mazda remans are not always great too, if you look up angel motors on youtube they did two vids of engines they got from mazda that were not in great shape. I'm in New Hampshire aswell and in my experience between NH and MA I don't think I would trust any dealer to ever take my car.

TannerRich

So I'm thinking about fixing all the small stuff and running with low compression (assuming it does have low compression) till the engine goes then just get another engine, I just changed my plugs and it starts easier. Next I'm going to figure out what's wrong with the OMP. It has a cold air intake so maybe that's why I'm getting the code for maf? Thoughts on this? And any ideas where I should get an engine. I also have a link I just made a couple quick videos, cold start when it lets me rev before limp mode kicks in and then the car in idle https://www.youtube.com/channel/UCTv...-_iiG51NhB-6QQ

TannerRich

https://www.rx8club.com/series-i-maj...tments-120276/
ive been reading up on OMP issues as this is my next step and this thread seems really interesting, has anyone done this successfully? I plan on putting an adapter on so I can have a reservoir of 2 stroke but I feel like it would be better to pump a little extra oil if possible.

CaymanRotary

You should really start with getting a compression test done. Make sure the engine is in good enough shape for the car to be usable. Then decide what you need to do.

MincVinyl

So my first thoughts on the cold air intake, check to see if there is honeycomb mesh inside the intake. The mesh is there to straighten the airflow so the maf can get an accurate reading. Doubt someone took it out, but who knows. Otherwise start checkin wires. Have you already checked the wires from the omp? It could be that the connector is simply failing, the rx8 has quite a few common issues that has to do with connectors.

Definitely don't rev it cold anymore, the bearings will get damaged without oil. But it does tell you at least that your fuel pump may be in decent shape although you are not sustaining high rpm.
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Pretty sure I saw this car for sale on facebook marketplace, lmao was gonna see if the guy would sell me his intake. For engine builders id probably look towards banzai racing or rotaryengine.com if I were to ever have someone do a build.

TannerRich

Yeah I'm working on a space I can work on the car easier. when I changed the plugs I put a little 2 stroke oil right in the engine so I could make the video. You probably did see it on facebook because thats where I found it. I did look at the wiring to the intake theres a connector not attached but I can't figure out where it goes. And the OMP I am having a tough time getting to it from what I can see the connectors are good but I got to get back under there and check it over because as you can see from the picture I posted it looks like it needs to be realigned And I'm trying to figure out where I can get a rotary compression test I'm in northern new hampshire so there's probably not a ton of rotary experts up here

MincVinyl

If you plan on sticking with the rotary financial burden and all I would just suggest getting a compression tester from https://www.rotarycompressiontester.com/

I'm down around Nashua, I'd let you borrow mine, but my pressure transducer got damaged.

Loki

iTrader: (1)

Can you show a picture of the connector?

If you can make it to Montreal, there's a good rotary expert in Terrebonne. Derwin tuning. It's what a couple of hours drive?

I pass through NH often to see my dad or for work, when the border is open again we should do a meet. Seems many folks from NH got RX8s lately

MincVinyl

@Loki sure helps when you can find running rx8s around here for under $2000. People selling before winter helps aswell.

BigCajun

iTrader: (1)

+1^
At one time RCT was renting them out.
Idk if they still do.