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I acquired an RX8 with a seized up motor a few weeks ago, just a quick introduction - and letting you guys know where I'm at.
Pulled a new motor from local junkyard and got it installed. I ran compression the other day and came up with 9.13, 9.13, 8.3 - 8.72, 8.72, 7.90. Unfortunately I'm only getting 160 - 170 RPM's during compression testing. Tested all the starter wiring and the battery. Those check out. Seems like my starter brushes are worn out.
Besides the starter I discovered an ignition coil which wont fire at all. I'm replacing that today. Hoping the car will fire up, even with the low RPM at cranking.
Let me know what you guys think, I now open the floor to questions, comments, concerns, tirades, barrages.
I replaced the starter (old one was only giving me about 160rpm.)
New starter is cranking at about 200-210. Motor started firing up and immediately shut back down.
So ignition system, check, compression, check, I'm down to fuel or vacuum. I did notice my brake light was pulsating while starting. - possible vacuum issue?
So I pulled the upper intake manifold, and the middle one, and after some investigation, found a bolt I stripped on the SSV actuator. I thought i got it tight enough, and when I felt it overtighten and start to strip. I stopped. hoping it would work lol. apparently not a great plan. During disassembly the bolt basically fell out. I also found a check valve I had installed backwards - the one going from the electronic vacuum dealy's to the upper intake. Not knowing they had a direction. In addition to those two issues, I found a port on the back of the intake manifold, that leads to two tiny ports inside the intake manifold. I had left this one open.
My plan is to cap that valve, I fixed the stripped bolt using copper strands, and I flipped the check valve.
I'm going to finish re-assembly tomorrow and give it a shot. If anyone has anything relevant to share I would appreciate it.
Pretty normal to need a new starter, you may as well get one. How did you manage a compression test with the starter spinning so slowly and the car not being able to warm up?
Replace all 4 coils not just the broken one. Number one killer of engines.
Take down and inspect the interior of your catalytic converter. Number two killer of engines, closely related to the first.
I did the pulse compression test using an excel sheet with an rpm adjustment on it, with the engine cold. I know this isnt ideal, but I'm working with the resources I have available.
This is the first time Ive replaced a motor so this is sort of a wild experiment. I chose the RX8 because its small enough to fit in my garage.
Also the catalytic converter was fine, although I deleted the oil metering and am going to run premix, assuming I get it running I'll cut the cat out of the equation. No emissions in KS.
I will replace all the ignition system components eventually, I'm just trying to get the motor to fire up before I get involved with the performance aspects of the vehicle.
Last edited by andrewball2019; 02-09-2020 at 08:16 PM.
I did the pulse compression test using an excel sheet with an rpm adjustment on it, with the engine cold. I know this isnt ideal, but I'm working with the resources I have available.
This is the first time Ive replaced a motor so this is sort of a wild experiment. I chose the RX8 because its small enough to fit in my garage.
Also the catalytic converter was fine, although I deleted the oil metering and am going to run premix, assuming I get it running I'll cut the cat out of the equation. No emissions in KS.
I will replace all the ignition system components eventually, I'm just trying to get the motor to fire up before I get involved with the performance aspects of the vehicle.
The test on a cold engine means nothing but it should be good enough to start and run. Deleting the OMP is generally a bad idea on this car. Better to run a Sohn adapter instead. If your ignition system, cat and everything else is fine and the car still wont start, I would begin to start checking fuel pressure.
I'll check the factory service manual for test location and pressures. I definitely have fuel, I'm not sure about the pressure though. The engine sputters while cranking, and Ive gotten it to start up for about two seconds if I flutter the throttle around.
Any thoughts on the pulsing brake light during crank being related to the reversed check valve? Im finishing reassembly and trying again tomorrow anyways.
Oh and the sohn adapter does look like a better option. I'll add it to the list of post idling motor purchases lol.
Depending on how you deleted the OMP, the computer will not allow you to rev over 3k without it. So yeah. You can premix and run Sohn adapter, they complement each other.
You definitely need the 2 tiny jet air ports connected to the intake. Critical for starting and idle.
Possible it's flooded from all your starting attempts?
Glad you got it started but the O2 sensor isn't used during startup. It's cold and can't provide any reading, so the fuel trims aren't modified at all. If it was overfueling, it might still be.
Well, my $150 junkyard motor didn't work out, the car starts, and warms up, and craps out any time it get's over or around operating temperature. I tested spark on all plugs during a previous issue. I'm going to check hot compression when I have some time later this week and see where it's at. I feel fairly confident the motor needs a rebuild. Which makes me a sad panda. I have an automatic 6-port, I've contacted one rebuilder who pretty much told me by the time I was done paying him for rebuild it would cost less to just buy a new motor from Mazda.
I see sets of rotor housings on eBay for about 800 bucks. And I have been eyeballing the $700 rebuild kit from Atkins rotary since I bought the car.
Is there a reason I can't start a thread in troubleshooting? It's just telling me I'm not authorized. Is this standard for regular accounts on this forum?
Well, my $150 junkyard motor didn't work out, the car starts, and warms up, and craps out any time it get's over or around operating temperature. I tested spark on all plugs during a previous issue. I'm going to check hot compression when I have some time later this week and see where it's at. I feel fairly confident the motor needs a rebuild. Which makes me a sad panda. I have an automatic 6-port, I've contacted one rebuilder who pretty much told me by the time I was done paying him for rebuild it would cost less to just buy a new motor from Mazda.
I see sets of rotor housings on eBay for about 800 bucks. And I have been eyeballing the $700 rebuild kit from Atkins rotary since I bought the car.
Is there a reason I can't start a thread in troubleshooting? It's just telling me I'm not authorized. Is this standard for regular accounts on this forum?
It's far better in your situation to get a remanufactured engine or an already rebuilt motor from a reputable rebuilder. Your lack of knowledge about how rebuilds work will cause you incredibly difficult problems. You dont just buy a rebuild kit and you are good to go. You need to first tear the engine down and go over what you need before ordering any kit. Save yourself a lot of trouble, money and time and get an engine that's already good to go.
You need a certain number of posts to post in other forums. Just keep your thread here, this works fine.
I did do a cold compression test, although I turned the rotors and verified the apex seal springs were functional with a poker as well.
I haven't resistance tested the ignition coils, I tried to last night but I'm not sure my multimeter is sensitive enough to pick up on the resistance.
The car still runs though right? It would be possible to do a hot compression test to get real numbers. Apex seal failure isnt the only way these engines lose compression. Could have a bad side seal.
It does run yes, I'll try the hot compression test next and we'll see where its at. I'll have results in the next couple of days.
It's your best bet because your symptoms may not be because the engine is bad. If it passes the test you can start investigating your ignition system and vacuum lines.
Checked coils today, the one advance sold me had the wrong tolerances, went back and exchanged it, tested it right there, the new one had the wrong specs as well, tried a different brand and got one that has the same resistances and now I've got solid spark on all 4 plugs.
I tested all the coils again, and they fall within spec, I also tested them hot, again within spec. The only thing I noticed is that the FSM says to test ignition coils pin C + and B - and look for some resistance. However the only way I was able to see resistance on this was by testing pin B + and C -, could this be some sort of issue?
Here's the cold stats, I didn't take the hot ones down, there were minor differences but no major.
Test 1, Test 2, Test 3
1.541, 1.048, 0
1.592, 1.099, 0
1.614, 1.075, 0
1.402, 1.115, 0
Fixed the limp mode issue, the OMP sensor was slightly off from where it was originally, I realigned it with the old imprint and now I'm out of limp mode.
I got to take it on a short drive, which was super awesome. It was nice to get some gratification out of this project. I've come a long way from a seized motor.
Still dies at idle after warming up. I'm running a hot compression test Monday or Tuesday, if the compression is bad it's getting tabled for a while. Good compression = parts shotgun.
I also checked vacuum while I was out there, It was idling rough by the time I got the vacuum tester on the car, and it was hovering between 10-12, steady rev at 3000rpm gave me a steady 20. While the engine was cold I got about 15 at idle.
I know I should be checking compression hot but I don't have the tester here, I rented one last time, I'm going to buy one in the next few days so I can check it.
Last edited by andrewball2019; 02-23-2020 at 05:34 PM.
Sounds like you've made great progress! Definitely test the compression hot. You actually were in true limp mode from the OMP sensor. Glad you found the cause and dont worry too much about your ignition system at the moment. At least it can run well enough to do a compression test. Interested in seeing your results. They will determine your next move.
I heard a whistling noise from my engine bay while doing the compression test.
Blew cigar smoke in the intake and found I forgot a gasket between the plastic oil receptacle and the engine oil receptacle. After installing a gasket and capping a random port (I have no idea what this port goes to, it's coming off the plastic oil receptacle). I'm still the whistle and having idle issues.
Blew cigar smoke in to the intake again and found that I am getting smoke somewhere beneath the plastic manifold, near the metal intake manifold. I'm not sure where yet, I did have to remove the VDI for a swapped intake manifold, and I reused that metal/papery gasket, although it looked good the whistly vibration style noise I'm hearing does seem like it could be that reused gasket.
I heard a whistling noise from my engine bay while doing the compression test.
Blew cigar smoke in the intake and found I forgot a gasket between the plastic oil receptacle and the engine oil receptacle. After installing a gasket and capping a random port (I have no idea what this port goes to, it's coming off the plastic oil receptacle). I'm still the whistle and having idle issues.
Blew cigar smoke in to the intake again and found that I am getting smoke somewhere beneath the plastic manifold, near the metal intake manifold. I'm not sure where yet, I did have to remove the VDI for a swapped intake manifold, and I reused that metal/papery gasket, although it looked good the whistly vibration style noise I'm hearing does seem like it could be that reused gasket.
First of all, numbers look great. Are they adjusted to 250 RPM? Well above minimum spec if so. This is fantastic news just on it's own. I love the cigar smoke trick, it works like a charm. Could be a bad gasket there yea. some of those are an absolute bitch to get to though.
it seems that the lower intake manifold I got from the junkyard was missing a bolt on the secondary shutter valve. Causing a vacuum leak which lead to failing idle.
Ive got a coolant leak around the thermostat somewhere, both windows are acting wonky, the shift linkage was damaged during thr engine swap, and the driver door handle is broken off. Other than that its great! Lol. Oh and I have a clunking sometimes which I think is motor mounts.
Also, im running premix so Im going to replace the cat with a straight pipe and throw a o2 bung on it.
02-06-2020, 07:24 AM
