Rexy-8

I just bought a 2004 RX-8 from a friend of a friend --140k miles. He said it needs new apex seals but I did enough reading online to know that actually it needs a new engine. But I got it for under $1k and aside from the engine the condition seems to be ok so I figured it was a reasonable price.

This is my first experience with a rotary engine and a Mazda so I know I've got a lot to learn. I've owned and wrenched on a 91 Toyota MR2 for a long time so hopefully some of what I've learned from that will cross over.

200.mph

iTrader: (9)

read the new owners thread 10x. yes apex seals can fail but its not always the issue. get a rotary compression test and if it doesnt pass the best route is a mazda reman keg

CaymanRotary

You'll want to go through the car fully and make sure the rest of the car is in good shape before replacing the engine. The engine is easily the most expensive thing to replace on the car but if you also have to fix other stuff it would make no sense. Even if you got the car for free if it costs more than the car is worth to fix it, then it's not a good idea.

Definitely get a compression test first, it's possible the engine is fine and some other issue is causing the problems.

Rexy-8

Thanks for the welcome and info. Reading through the New Owner thread right now!

Rexy-8

I was able to get the car started but once it warmed up it would not idle. If I pressed on the gas pedal to keep the revs up, it stays running but the RPMs tend to jump around every few seconds. For instance, if I push the pedal down to bring it up to 4k, it may suddenly drop to 3k for a few seconds, then 2k, then back up to 4, then 2.5, etc. all while holding the pedal at a constant position. The PO said once it was warm he couldn't restart it until it cooled down, but I was able to restart it with some extended cranking.

After reading through the newbie thread I think I've determined an initial course of action -- do a complete tune up. plugs, wires, coils, coolant. then see how it runs. I figure if I have to replace the engine I can still reuse all those parts on the new one.

I would also like to do the compression test but the nearest Mazda dealer is an hour away so I'm going to have to DIY. I saw a video on YT about how to do it with a regular compression tester (which I have) but it's a bit involved. I thought I saw on ebay a rental service where you "buy" it and send it back in two weeks but I searched today and couldn't find that.

CaymanRotary

Definitely do the compression test first before investing money into those parts you mentioned. Are there any engine codes?

Rexy-8

The CEL was on but I didn't have my OBDII dongle at the time. Next time I'm at the car I will read the codes.

Regarding the compression test, any opinions on this technique?

CaymanRotary

It does work just won't be totally accurate. A rotary tester is definitely preferred but it will give you a rough idea of what compression is like. Definitely read the codes and give the compression test a go. Remember, the engine needs to be warm before performing the compression test.

mgilham

Hey, if I could put my 1 cent in here, it sounds like a plugged cat, caused by bad coils. You can check the coils by grounding a spark plug with a jumper cable. Pull each plug wire, connect to the spark plug and have someone turn it over. Repeat for all 4 plug wires. My wife and I bought an 04 RX8 new and at 70k miles it would barely run. Turns out after chasing my tail for about a month, 2 coils were completely dead, one was weak and one had good spark. I had a compression test ran and was scheduling a motor rebuild when I decided to check the coils based on what I read on this site. I also upgraded the under powered starter, again based on what I read here. When these guys say RX8 coils go out at 50k miles and the starter is junk BELEIVE IT! Lack of spark put unburned fuel into the cat burning out the 1 of 2 honey combs plugging the cat and the muffler. I bought LS2 coils from a wrecking yard, built a bracket and mounted them in that tiny little spot where the originals were. A ton of work and time. I would buy a coil kit if I had to do it now. I rodded out the remaining portion of that honey comb by cutting a hole in the cat and was able to clean out the muffler but it caused an o2 code. I thought it sounded great but the wife said it was too loud. I didn't like her driving with a constant engine code so wouldn't know if something else was throwing a code so I bought a cat off of Amazon. Keep in mind I will step over a dollar to pick up a dime.... I did a little test drive last night after replacing a right rear wheel bearing, brake pads and rotors and was reminded why I shouldn't drive this car, holy **** this thing is fast! Damn near had another heart attack! The car has 130k on it now but runs better than brand new. Thanks to the guys here on this site!

Rexy-8

I got my OBD2 dongle plugged in and read the codes using the "Torque" app on my phone. Codes were:

P0130 - O2 sensor circuit, bank 1 sensor 1
P0506 - Idle control system RPM lower than expected
P0661 - Intake manifold tuning valve control circuit low, bank 1

The car actually started pretty easily this time and seemed to run better but it still would not idle once it warmed up. Also, the radiator fans did not come on even when the engine temp got over 190 (I watched the temp with the OBD2 app). Afterwards I tested both fans with 12v and they both ran fine so I'll have to diagnose why they are not turning on before I drive it.

Another thing I noticed is that even when it got up to temp, it was not hard to restart. The PO said he could not start it once it was hot. Though maybe letting it idle up to temp is not quite the same as driving it and then shutting it off.

I think I am going to give it a tune up with plugs/wires/coils. The PO said they were not replaced any time recently so I think it's a good starting point.

CaymanRotary

The coils/plugs and wires should give you a stable idle and solve that code. The p0661 is those 3 solenoids by the firewall under the UIM. You will also need to replace all 3 because if 1 is going bad, the other 2 aren't far behind. It requires to remove or at least loosen the UIM to get to them so its better to just do all 3 while you are there. The last code is your front O2 sensor. This does go bad over time and needs to be replaced. You should also drop the cat while you are at it and make sure it isn't clogged.

First thing you really should do before buying anything is a compression test. You really don't want to be dropping hundreds of dollars on an engine in unknown condition.

Rexy-8

There's a small garage in town that seems to work on a lot of imports, some quite pricey looking. I'm going to check with them to see if they can do a compression test. Even then, I'll still have to get the cooling fans working, I definitely don't want to overheat it!

0-TO-100_Real_Quick

What area do you live in?

Rexy-8

northeastern PA

200.mph

iTrader: (9)

theres a few of us on this site in nepa.

Rexy-8

Cool

The garage I called last week never called me back to say they could do the compression test. So I have to assume the answer is "no"

200.mph

iTrader: (9)

where in nepa? if ya dont want to post it on a public forum shoot me a message. im not far from scranton

Rexy-8

So I installed the plugs, wires, coils and scratched my forearm up pretty good in the process -- but I'm used to that from working on my MR2

I'm not really sure how much better it may run now as I didn't take it for a drive (because of the cooling fan issue) but it still wouldn't idle after warm up, so I want to replace those three solenoids next. If anyone would care to suggest an online vendor/vendors for purchasing OEM Mazda parts, I'd gladly accept the recommendations!

CaymanRotary

You really need to perform a compression test on this engine. This is the main symptom of low compression.

RastaRx-8

its actually a very good indicator that your engine has been overheated and continued to be driven.. which does happen a lot with the dummy factory water temp gauge that is very inaccurate. Any time i hear that an rx8 wont restart after warm its usually this. The motor has taken in coolant into the rotor housing/combustion chamber and is trying to ignite it... causing your housing surface to corrode and lose compression over time plus reducing burn and compression while its still in there... rebuild the motor now before all the other parts fail you will probably just be buying 2 new housings

Rexy-8

Yes, I know. I was hoping to find a local garage that could do the compression test for me but so far have come up empty. But even then, I have to get it running well enough to make it there unless I trailer it. I think I'm going to try that youtube technique of doing it with a regular compression gauge.

And actually, I have been able to restart it after it's warmed up, counter to what the PO said, without any undue effort. Though warmed up from idling may not be quite the same as warmed up after driving. Once I get the cooling fans working I'll be able to drive it and find out better. Hopefully it's just the 40a fuse. I'll be checking that today.

Williard

iTrader: (18)

Rexy,

like 200 asked, where in PA? Several of us are in PA and many of us have rotary specific compression testers and most if not all are far cheaper than the dealer and far more accurate than a piston compression tester.

Travis

Rexy-8

The car is near Berwick. That would be awesome if we could work something out.

Rexy-8

I did some more work on the car recently.

I cleaned the MAF sensor and repaired a cracked hose that goes from the crankcase to the intake. This seemed to make it run smoother but it still would not idle once it got warm.

Yesterday I removed the catalytic converter to inspect. It did not look like it was really clogged but I knocked it out anyway. Afterwards I drove it around a bit and it sat and idled pretty smoothly without stalling. Also, the fans seem to work fine. I watched the temp with my OBDII and when the coolant hit 203F the fan came on.

So each time I do something the car runs better which is encouraging but it is still hard to start when hot which is discouraging. I'm going to do an ECU clear today and see if that helps.

RastaRx-8

Great that you are fixing her up , but Im not sure if you are understanding how bad for your motor it is to keep trying to run it if it has had a coolant seal failure from a previous overheat... you are going from no damage internally just rubber seals bad to both rotor housings being trash (700 each ) ... i would just bite the bullet and rebuild it now while you have possibly good parts still inside