I've got a 2004 RX8 that is my wife's everyday driver. It has 35000 miles on a rebuild. It lost a little power, which felt like the typical case of coils going out. Replaced plugs and coils (good plugs, cheap coils) and it felt perfect for about 2 miles, then (once it was warmed up?) I could barely get it home.

Cat was completely shot. I gutted it and cleaned out all the debris.

Car will now start cold, but dies once warm and will not start warm.

Just did a DIY compression test, pulling the schrader valve and taking video of the test. Numbers are in PSI, normalized using the Rotary Compression Calculator,

FL: 80 74 74
FT: 80 74 74
RL: 85 79 79
RT: 85 79 79

From reading the test instructions it sounds like this method reads low. Are these numbers low enough that the engine is toast, or might there be another issue? It seems like a big coincidence that it went from losing a little power to being completely undriveable by replacing plugs and coils.

Thanks

 

It's toast if those numbers are at 250rpm.
Did you take apart the intake to replace the coils? Possible you left some stuff unplugged?

It could be low on compression AND have other issues. The clogged cat certainly did you no favours.

 

I'm not very optimistic. Trying to figure out how much time and money its worth to chase down any potential other issues.

I also just found out it is leaking oil and the pan has a big ding in it that I haven't ever seen before. Don't know if that can be related. What happens if the oil is over-filled? Will that cause a leak anywhere? Yes, I have a reason to believe it may have been up to a full quart over filled (don't ask). It is obviously dripping from the pan, but I know that doesn't necessarily mean the leak is anywhere near the pan. I'll clean it up tomorrow and see if I can tell where it is leaking from.

 

Out of ignorance I initially used to race with an extra qt of oil (around 2005). Some engines can benefit from that, but not the Renesis as I later figured out. It won’t really hurt anything or cause leaking in itself, but if you have a lot of combusted gas blow-by into the sump it can enhance the chance of blowing oil up through the oil fill extension and into the accordion tube at the throttle body inlet. Which if blow-by is bad enough will happen even at the proper oil level.

Leaks are almost always caused by bad seals/gaskets or in your case potentially a puncture in the pan itself. So the silicone sealer gasket at the pan, the oil level sensor gasket in the LH side of the oil pan, the front and/or rear e-shaft seals, the oil pressure sensor at the upper LH rear side of the engine, the oil filter gasket, filter stand gasket, and oil cooler piping connection at the upper LH rear corner of the engine, the oil cooler piping connection at the lower LH front side of the engine, and the oil metering pump gaskets on the lower RH front side of the engine are the potential culprits.

 

Still not hopeful. More checking and cleanup and it still starts fine then dies after a couple of minutes when it warms up, then won't start again until it cools off.

My question now is why am I NOT getting a CEL with a completely gutted Cat?

 

It varies a lot and is the least of your problems. Engine is likely burnt toast

 

I totally get that. I was just curious.

I'm figuring out what to do with it now. I don't think I'm going to fix it because the combo of a new engine and a new cat is pretty high, but it is in good shape otherwise, good quality new clutch, tranny from a low mileage 2006 plus I have 4 new struts in boxes that I am not going to be using. I'll get next to nothing for donating it, so I guess I'll see if it is worth anything to anybody locally for parts or to rebuild.

 

It seems strange you suddenly have the dying issue.
Checked the plug wires were snapped on tight?

Did you jack it up to gut the cat or on a lift?
If you jacked it up maybe a little blow by oil was sitting in the intake and got stirred up enough to blow all over the MAF?

Clean the MAF sensor and ESS?
Did you unhook the battery and reset the NVRAM?
Check the terminals and grounds to see if you might've knocked one loose?
Wouldn't hurt to check those if you didn't.

 

It was jacked up on an incline (driveway) while oil level was too high, so blow by is definitely a possibility. I'll clean the MAF sensor and ESS. Unfortunately I do not think that could explain the classic low compression symptoms. Symptoms are the same with old ignition coils as well as a new set.

I have reset the KAM and the NVRAM.
Strong battery and starter and good spark. Classic low compression symptoms. It starts fine cold, then dies when it warms up and won't start again until it cools down. I tested the compression for all three faces of both rotors using the DIY method with video, and they all come back consistently low.


Thanks.

 

If you have an OBD reader, read your fuel trims while it warms up. The sudden onset is uncharacteristic of low compression. You could still have low compression, but its possible it was tolerable until whatever work you did added another issue on top of it.

Fuel trims should be near 0 once it gets close to warmed up. If the fuel trims are pegged at +25 your problem is not compression. If they're 0 ish all the way through and it dies then I give up, it's compression.

 

I have an 07 mt with a mazdaspeed cold air intake and 89900km that I think has low compression. Replaced coils, plugs, and wires as well as an oil change at 87000km. I drove it during last summer and near the end it started to have a rough idle, misfires, and dies when coming to a stop sign. One time coming home for work the car died at a stop sign and wouldn’t start, sounded like it was flooded. So I did the deflood procedure and it eventually started and was able to get it home. Wasn’t able to start it for a month and a half so I bump started it by getting towed behind a truck. Once running it had significant power loss and hesitated at 5000 rpm, but was able to get it to my dads shop for the winter to store. Fast forward this weekend after doing a ton of searching I decided to get a fuel pump and starter. After replacing them it started after about a 8 second crank and was idling terribly from 1500 to 750 rpm and was still misfiring and then eventually died. Tried to start again, but it was flooded so deflooded it and started again after about 8 seconds, and same thing but the idle started to steady around 1000-1100 rpm after about 5 minutes. After 15 minutes of same idle took it for a drive and still had power loss but didn’t seem as bad as before and hesitated at 7k. I was able to get it back home and read what codes it had, it had always had the cel on because the the intake but had never read the codes till now since I just got one. My codes it read are po506
po410 po171 po411. I’ve redone the intake and made sure there is no leaks, cleaned throttle body, mass air flow sensor, ess. Forgot to mention when changing my plugs i found that they they were all trailing plugs and no leading, so now I’m not really trusting what the last owner. So today I’d figure I’d check if the cat was gutted and it was. So I’m baffled as to what to do next, does it need more time to learn fuel trims? Is it low compression?

 

The intake shouldn't really cause any codes by itself... do you know what code it had before?
Was there oil in the intake tract when you took it apart?

It sounds like you're getting unmetered air in somewhere (P0171), and that your secondary air pump is missing or broken. The unmetered air thing would also explain the symptoms. It doesn't really sound like low compression (but is not proof that it's not ALSO low compression). Are there any open cracked or hoses anywhere after the throttle body? Is the secondary air pump in fact installed? Does it run better or worse if you disconnect the MAF, and/or if you disconnect the Baro sensor?

Are the spark plugs connected to the correct coils? Any other mods or previous-owner problems?

 

Thanks for the reply! I do not know what codes I had before because I never had a reader until now. I have not taken apart the the upper intake manifold yet but tomorrow when I’m able to work on it I will take it of and take a look. When I took apart the intake ducking to the throttle body I found there was no oil as well the throttle body. I don’t have an air pump ( assuming previous owner took it off) Could not see any noticeable cracks or unconnected hoses after the throttle body. Haven’t tried running it without the maf or baro but tomorrow I will see if it makes a difference. I’m pretty positive that the plugs are connected to the right coils, but now I’m questioning myself lol. No known previous issues with the car as the owner didn’t really seem to know the car well. I will attach a picture of my engine, doubt it will help, but it’s a visual. Thanks again

 

Thank you for the reply! I have no idea what code it had before because I had no reader until now. There was no oil in the accordion tube or throttle body, but I’m going to take off the upper intake manifold to see if there is any there and to check for cracks. It looks to me like I have no air pump, the last owner took it off. No open or cracked hoses that I can see but I will take a better look. I will also disconnect the maf and baro to see if it helps. I’m pretty sure that I connected the plugs to the right coils, but I’ll take another look and make sure. No other problems that the previous owner told me of, said it’s always ran good. I will attach a picture of the engine bay, i dont know if that will help or not. Thanks again

 

So a couple of things...
- have you checked the VFAD vacuum nipple underneath the throttle body? It's put of sight, you have to feel for it. It should be capped.

- it's not clear but it looks like a vacuum line going to the air pump valve is missing, which might mean another uncapped nipple. It's the black hat shaped thingie on the passenger side of the engine, there is supposed to be a line going from the oil neck or manifold ( I don't remember which) to the back of it.

Might want to google rx8 vacuum diagram and generally check that things are plugged in the right places

 

The vlad hose is still connected to the intake, so that’s all good. I found the hose that was supposed to be on the air control valve and it was capped with a screw, so I put it back on and zip tied it together for now till I get hose clamps. Then capped off the other side of the air control valve. I checked everything over and found nothing else out of place. My car has no exhaust on it right now because i was checking to see if my cat was gutted and to check for leaks. So I didn’t really want to run my car for very long because it was late I started the car after about a 6 second crank with touching gas, it was idling rough again so I unplugged the maf then the car died. Tried again with the maf unplugged and i only took 3 seconds no gas then idled steady at 2100 rpm for about 5 mins till I shut it off because of noise. I’m getting new exhaust hangers tomorrow so I’ll put it back on so I can do better testing. But could the maf be the issue?

 

Hmmm but wait. You don't have a VFAD any more if you have the AEM/Mazdaspeed intake. So what is that hose connected to?

I don't think it's the MAF itself, but the fact that the car ran well with it unplugged firms up the notion it's a fuel trim/unmetered air issue. I mean definitely clean the MAF with the right cleaner to be sure, and check for damage, but it's rarely the sensor.

Another place to have a look is at the vacuum box at the back of the upper intake manifold that feeds vacuum to the oil injectors. It can crack.

 

The vfad is connected to the intake, there is 3 hoses coming off intake and the vfad is one of them. I found the hose that wasn’t connected, it was the one from the bottom of the upper intake manifold that went to the vacuum chamber. So re connected and ran really good all day, Steady idle at 850rmp, didn’t die coming to a stop. Cleared all codes and none have popped up for a couple drive cycles. Was still having starting issues tho, and noticed that my battery terminals were very loose and they were as tight as they go, so I bought new ones then switched them out. Now still having starting issues (6-8) with needing gas and is dying when I come to a stop again. I still have a good idle and no cel. So did I reset something when I discounted the battery? Thanks for all the help so far!