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Engine Rebuild - Engine Stops Running After Several Minutes - Won't Idle
Hey guys, I'm not exactly new to the forums but I guess I don't have the post count to put this anywhere else. I'm going to try to provide as much detail as possible in this post so I apologize in advance if it gets lengthy.
I've been the owner for a 2004 6 Speed MT RX8 since February 2006 and have been through many various troubleshooting and DIY stuff here on the forums. I've done quite a bit of searching and can't really turn up the issue I'm having so any help would be greatly appreciated!
Anyway, my RX8 got its first proper engine rebuild about a month ago from a reputable rotary builder. The old engine had approximately 88K miles and died due to lack of compression when warm (hot start trouble). The short of it was that I hadn't really treated it that well over the years and had some pretty bad housing wear along with some other "not so common" wear according to my builder (E-Shaft, Rotor Bearings). This was a Mazda Reman for the record.
My builder and I opted for brand new housings and resurfaced irons, brand new e-shaft, brand new rotor bearings and of course all new seals/o-rings/gaskets. Essentially, my engine is almost 100% brand new with the exception of the re-used rotors. To the best of my knowledge it was unmodified from stock in that it has not been ported or otherwise changed. The only exception is a higher PSI oil pump at my builder's recommendation.
I've got the engine back in the car, fully re-assembled, all sensors, hoses and wires seem fine. I have no leaks as far as I can tell in the coolant or oil lines. The issue I'm having is pretty much exactly what the thread title says. My engine starts, runs a bit rough (as to be expected), levels out and then after about 4-5 minutes of running shuts off. The shutoff doesn't appear to be mechanical in nature (no sounds or feeling, just a clean fuel cut) and almost always happens within the first 5 minutes of running the car. I have repeated this process 8 or 9 times now and the engine will always shut off, no matter how much throttle I'm giving it, after about 5 minutes. I have not broken 4K RPM during the break-in and have not really driven it more than about a quarter mile. Additionally, the car won't idle. If it drops below 500 RPM If I'm quick I can revive it. It is also worth mentioning that I have to throttle assist slightly to get it started.
I had been running it on old plugs and coils for the break-in and definitely had a lot of trouble getting it started up initially. I've pulled and cleaned the plugs several times during this process. The first few times, the plugs were pretty dirty as expected. The rear plugs always seemed more dirty though up until the last few pulls. These plugs weren't in great shape to begin with. The last couple times I've popped them out though they've been pretty clean. I decided to put my new coils and plugs in today just for kicks. I definitely had a much easier time getting started and everything sounded quite a bit better, even felt better (placebo affect maybe but I don't think so). Still shuts off after 5 minutes though.
I'm getting three codes coming up on my cheap OBDII reader as follows:
Of those, all three are in the "Pending Faults" list. Only P0171 is in the "Confirmed Faults" list. I'm not sure if this matters.
The car will not start again after the 5 minute shutoff for about an hour regardless of the temp readings. It is important to mention here that the car is NOT over heating. Temps are reading around 205F at the hottest but I've had the car shut off at 175F, 195F, and 205F or anywhere in between so this does not necessarily appear to be temperature related. The thermostat and radiator are brand new.
My starting RPMs look pretty good IMO, above 350RPM initially and up to 475RPM when the ignition kicks in (but won't start).
I've cleaned the MAF and the E-Shaft sensor. I know my front O2 sensor looks like hell and I'm considering replacing it. I have the original CAT/Midpipe assembly but the Cat is gutted (Cat died some time back). My car is pretty much bone stock other than that. No aftermarket header, midpipe or CAT Back. No aftermarket ignition, intake, tune or anything else to speak of.
I have eyeballed the entire intake system, hoses, intake manifold etc. to check for obvious things I might have missed. I've tested the solenoids as well (checked out good). Admittedly, I have not thoroughly gone over the intake/checked vacuum though and seriously wonder if this could be the issue. I do find it strange that it runs so strong right up until it shuts off though, but I do not claim to be a mechanic or rotary pro.
And before anyone asks, yes I'm also contacting my builder for suggestions and yes I followed his instructions. I'm just interested to see some other responses and possible thoughts on the issue as well.
Any insight you guys have is greatly appreciated. Thanks!
Hah okay, although my searching didn't turn up much, I did see a few other similar posts while just manually scrolling. Apparently I'm bad at searching or something. Anyway, still interested in any thoughts you guys might have. I've seen suggestions in other posts mentioning to check vacuum or just drive it. I guess my concern with driving it is stalling out and not being able to start again for an hour. I already dealt with that with the low compression/hot starts!
It would appear to have fuel pressure and spark but won't start. I get this impression because when I pull my plugs they do have fuel on them after trying to start it and I do hear the pump pressurize. Also, if I hold the pedal in when starting (the no fuel de-flood procedure if I'm not mistaken) the engine turns over at about 350 RPM. If I let out and try to start normally, I get up to about 475 RPM and it sounds like its firing and trying to start but won't. It sounds like it's right on the edge of starting from my experience with the car. I've had the battery on charge and jumped it with no luck either. The battery is brand new.
I've tried the 20 brake pedal ECU reset when it won't start after shutting off and this does not appear to decrease the start time.
I have started it once without the MAF purely on accident, but I don't recall how well or long it ran. I have not tried this again recently though so I'll give it a shot this afternoon.
I would check the fuel pressure 😊 Low fuel pressure often manifests like that ...
Also disconnect the battery to reset the ECU. The 20 stomp only resets part of it.
@dannobre: I'll try pulling the negative and holding the brake to clear out the caps and fully reset the ECU. I've done this before but I have not checked to see if this reduces the startup time after the shutoff though. I'll also check out the fuel pressure. The pump was replaced under recall when I had my compression test done right before the rebuild and my fuel lines are securely hooked up.
@Charles R. Hill: Thanks for the suggestions. The throttle body was cleaned before re-install but it's easy enough to check again.
I'm very confident in the fuel injector install as I left the secondary yellow injectors in place when I tore down the engine. I reinstalled my red primary injectors and I had very good picture references with labels for the connectors. I'd like to try to diagnose the issue with the engine as assembled as possible as tearing it down again inside the car really sucks, but I'm definitely not opposed to doing whatever it takes.
Today I was going to really dig into the vacuum/air intake side of things since I can do that with everything still assembled. Do you guys think there's any chance that this could be the issue, especially given then P0506? I noticed the VFAD has air hoses that ultimately connect to the throttle body if I'm reading the diagrams correctly. Could a leak here be the culprit?
Tried capping off the nipple behind the throttle body for the VFAD, no luck.
@dannobre: No luck on starting it without the MAF plugged in. I'm not sure what that means. It fires up without the MAF but instantly dies no matter what I do with the pedal. Also, a full ECU reset with battery off and brakes held in did not start me up again after it died.
I decided to drive it down the street, started off low power and rough but came into its own right up until it died on me mid u-turn with he clutch in and me feathering the gas lol.
I did notice I had a whopping +25% fuel trim according to the reader. I'm going to guess I'd probably notice a vacuum leak causing that much trim right? Either way it does seem to either have too much air or too little gas. I think I'm going to have it vacuum tested and maybe its also time to check out the injectors. They are likely the originals with 135k miles on them, dunno if they were replaced in the reman.
Sorry wasn't ignoring the fuel pressure check, I just am not sure how to test it. I don't have any gauges. I'll search the forums and see if its something I'm up for or should have it done somewhere else.
@Zig: Yeah I feel like if I could get it somewhere I could drive it continuously that might help. I'm considering having family tow it to a nearby lot and giving it a shot but I'm still on the hunt for issues while I've got it where it is.
Hey guys just an update. We took the UIM apart again today and resealed the gaskets. I double checked my injector harness wiring per the shop diagrams and all is correct there. I was pretty meticulous about that during uninstall/reinstall. I cleaned my MAF with electronic cleaning spray again. I also cleaned the throttle body and oil filler neck again.
Now for the interesting part. My SSV wire harness cables were stripped bare for both leads and were wrapped around each other...ouch. We fixed that issue and also tested the SSV and VDI (VDI right?) actuators and they appear to be moving just fine.
The car now starts and held idle for over 30 minutes today. I decided to give it some throttle while being stationary and as per usual after about 5 minutes it dropped briefly to 1k RPM before shutting off.
We decided to go for a drive and ended up driving it for 30 minutes between 1st and 4th gear up to 55 MPH and always over 1k but below 4k RPM. Drove pretty good, lacked some low RPM response as expected at this stage but over all ran good. Pulled it back into the shop and it instantly stalled again.
The plan for tomorrow is to replace the front O2 sensor and check vacuum per the shop manual with a vacuum gauge. Every time the car switched into closed loop and used the O2 sensor it shot straight to +25% STFT even when driving and getting air into the intake.
I still haven't had a chance to check fuel pressure and I'm not writing that off completely but do remember that I drove this very same vehicle to its current location about 2 months ago with no incident. The pump itself is quite literally brand new. Still, I understand things happen.
I'll give you guys updates when we have the new O2 sensor in and see how vacuum looks. Plan to do another evening drive too and see how that goes. Any ideas based on the new info is of course always welcome. Thanks again guys! Progress!!
Edit: Just FYI my two problems are still no idle after throttle changes (but now idles on its own from startup pretty much indefinitely), and won't start while hot (though my builder mentions this is a common issue when breaking-in).
Another update. Today we hooked up the vacuum gauge and saw about 10-12 in/Hg at the LIM nipples. Not sure if that's normal or not tbh, I was under the impression it would be a little higher. We replaced the MAF o-ring and took it for a drive. Its definitely opening up more, the idle was a bit stronger today, up from the 700s into the 800s. After the drive we brought it back to the shop accidentally stalled. We think the stall was just from putting load on the clutch and not enough gas though.
Anyway, we let it cool to 150F (it would not start at 170F). It started up with some hesitation so I decided to let it idle. It cycled between 700 and 1200 RPM idle for about 45 minutes and eventually settled in the 830-950 range, never dropping below 800, never going above 950. Total idle time was about 2 hours. The engine is definitely running smoother, no more shaking or super rough idle. I hopped in, pulled it into the shop and gave it some revs to 3500 RPM or so. Once that seemed smooth after a few goes, I revved to ~3700 RPM and let it drop down on its own. It caught around 1100 RPM, dropped to about 800 RPM and held idle FINALLY.
Things are looking better so tomorrow we have a small oil leak in the pan to fix and I think its time to get it back on the road for the break-in period. The plan is oil change at 500 miles, and under 4K RPM for the first 1K miles. I'll update again after that and let you guys know how things are looking.
Hey guys, here are my spark plugs after 150 miles. Rear plugs in the left, front on the right. What could cause the rear to be black but the front to be literally pristine. I expected some buildup on both. What's got me baffled is how clean the front are.
My understanding is that rich =black, lean it's lighter/whitish? Pristine is?
Car does drive and idle now but after 150 miles I'm hitting a 3500 RPM wall in 3rd. Have been up to 6th at 70 mph. More than usual backfiring on the rebuild. Still high stft. Fuel seems ok, fixed a small leak in the vfad hosing. Replaced front o2 and MAF just in case/preventative. Still thinking I've got vacuum issues tough, still haven't had a chance to get it smoked.
Just curious what you guys think could cause such a huge discrepancy in the condition of my plugs. They are new coils and plugs by the way.
Hey everyone my names adam and i got a 2004 rx8 and i got a problem and dont know what it is i need help. Ok so when i go out to start it first thing in mornin it will run perfect i can put it straight into drive and it works but as soon as it warms up it falls on its face it will just die and it will start back up sometime and sometimes it wont. But if i go out in the mornin and start it and leave it in park it will stay idleing and you can rev it up but once its warm and you go to put it in drive it dies i really need help please
A compression check would likely be the first place to start. If that is OK there are many places to go from there. What is the age of the ignition components? If you can't get a compression check done pull the.plugs and see of they are all firing
Often a T coil or wire failure will show up as idle problem...and it runs decent other than that
Hey zrock, did you figure out what was wrong and why the front spark plugs were not firing? I have been following the thread and was just wondering if there was a happy ending to your rebuild.
I have been contemplating doing a rebuild on my 2009 RX-8.
Pretty great builder to send you on your ways and not troubleshoot the issues that have manifested post-rebuild. Not to mention the leaky oil pan, stripped wires, and vacuum leaks. Sounds like someone may have played you for a fool, i would seriously question the work and test the compression and take a closer look at the car.
Hey guys, so with Irma and work I hadn't had a lot of time to work on the car and we gave up on fixing it ourselves. We decided to take it over the Jeff at Maztech in Tampa. Let me just say that Jeff and Steve are absolutely amazing. Top notch service, friendly and very knowledgeable. I'd recommend them hands down to anyone with a rotary or other Japanese cars as that's their specialty.
The issue turned out to be that my front rotor primary injector wire harness had a bent prong causing it not to inject fuel correctly. The reason the car surged and ran fine after 4500 RPM was due to the secondary injectors kicking in.
The oil leak turned out to be from the oil galley plug on the rear iron. Jeff and Steve figured it out pretty quick and patched me right up.
I drove the car home this evening and oh man how I've missed a rotary with good compression! Car runs absolutely amazing. That being said, the builder did a fantastic job with the build as compression was "perfect" per Jeff and Steve. The oil leak was a mishap I need to get back with the builder on as the irons were sourced by him, but I cannot really fault him for not knowing of the leak in advance as it only leaked under pressure. Every other part provided appeared to be in top order and resulted in an excellent rebuild. I'll name the builder once I get the final stuff sorted out, but suffice to say, I'm not upset with his work.
Thanks again for all the suggestions guys. So glad to have the 8 back!
Edit: Also real quick @Xero Ryuu, I provided the builder a bare block and he provided me it back rebuilt. He was very friendly and helpful, the other issues were entirely on us and our lack of knowledge regarding re-installing a rotary in an 8!
I have a rx8. I bought a not running rx8. Did new spar plugs maf sensor and coils. After this it did run good but when It w was warm I would not start. So I did a rebuild.
I rebuild the engine and cleaned the engine bay.
First time starting the rebuild engine started good after cranking for oil pressure without the plugs.
The engine runs for 2 minutes then it starts to idle rough. It goes high idle then low idle and dies.
When that the engine is warm it idles nice.
The engine sounds happy it had good power starts quick.
The problem is that It does not idle wel when cold.
I have checked for air intake leaks but I can't find any.
I have a rx8. I bought a not running rx8. Did new spar plugs maf sensor and coils. After this it did run good but when It w was warm I would not start. So I did a rebuild.
I rebuild the engine and cleaned the engine bay.
First time starting the rebuild engine started good after cranking for oil pressure without the plugs.
The engine runs for 2 minutes then it starts to idle rough. It goes high idle then low idle and dies.
When that the engine is warm it idles nice.
The engine sounds happy it had good power starts quick.
The problem is that It does not idle wel when cold.
I have checked for air intake leaks but I can't find any.
Does anyone have a idea what to do?
Check that the injectors are hooked up correctly. It's easy to hook them up wrong. Also double check the coil/plug wiring just to be sure
^^this, if not that, then get some airflow, fuel trim and temperature data via OBD2. It'll tell you if there's an air leak you haven't found or give other leads.
08-08-2017, 08:02 PM
Engine Rebuild - Engine Stops Running After Several Minutes - Won't Idle
