Hey guys, new here, and wanted to ask what to check on a car that I am interested in purchasing and jumping into the rotary world. It is a 2007 RX8 Touring with a 1.3 L R2 motor. I was told by the owner that the car is fine with one flaw. After it starts up it runs for about 15 minutes and then it turns off. He said he had a mechanic look at it and that the only repair it needs is a catalytic converter. He says after the car shuts down it takes another 20 minutes or so for the car to cool down and be able to start up again. For those experienced here, is this a plausible diagnoses? What else could cause this kind of shutdown? And what else should I check for when I go look at the car? Any info is welcome, thanks.

 

An inability to idle when warm is a classic symptom of low compression. Before you buy get a compression test done (a rotary-specific compression tester must be used). A Mazda dealership or a rotary engine shop would be able to do this.

There is also the possibility that the fuel pump is failing, but in any case you should get a compression test before buying any used RX-8, regardless of symptoms.

 

Walk away, you're buying problems with this car.

 

Is the low compression issue a common thing in the RX8's? If it is a compression issue, what are the fixes and costs involved? Compression issues are new to me, I've never had that sort of issue in any of my previous cars.

Will it at some point involve a motor swap? I've swapped a motor only once before in a grand prix and it was a pita but it was worth it just for the experience. Not sure if I want to go through all that trouble to save a car that I dont fully know yet. As Loki suggests I might walk away but I would like to learn more about these issues, because sooner or later I will be getting an RX8 since it was one of my dream cars since it was released.

 

Do yourself a huge favor and read this thread all the way through.

https://www.rx8club.com/new-member-f...t-here-202454/

Compression failure is unfortunately pretty common in RX-8s. Some fail due to defects, but most fail due to owners who do not understand what they have or how to maintain it properly.

Regular mechanics usually fail miserably at diagnosing problems in cars with rotary engines.

You must have any RX-8 you are considering buying compression tested at a Mazda dealership or reputable rotary shop. The test requires specialized equipment that only they have.

The only solution to a low compression engine is to have it rebuilt or buy a reman. The cost is typically $3000 to $6000 depending on who does it and how much labor you can contribute.

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Thanks Steve, so does this mean that his "its just the cat converter"story total bs?

 

not totally he could of had a mechanic tell him that a lot will just guess based on the symptoms your having kind of like a doctor but for cars, he maybe took it to someone who isnt familiar with rotaries

 

I'm not going to say he is dishonest, but his mechanic probably has it very wrong. Bad cats come into play 2 ways in this car.

1. The engine dumps fuel and oil into the cat, which causes it to clog. The clog robs performance in the higher RPM range.
2. The clogged cat pushes tremendous amounts of heat back on the rotors, which causes eventual compression loss and engine failure.

The main reason this happens is found in the ignition system. The coils, wires, and plugs are wearable items in this car, and they weaken over time and tend to fail around 20K miles. Once the ignition is weak, fuel and oil burn becomes incomplete. See number 1 above.

Read the ignition health section in the thread I linked for information on how to prevent this from happening.

A bad cat causing the engine to shut down after 15 minutes does not fit with any reasonable explanation that I can think of. What is more likely is the ignition system killed the cat, which killed the engine.

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Thanks again, that's some great info right there. Also read the new owner thread.

Yea I'm def walking away from this one, it just sounds like the problems of this car were due to low maintenance from the previous owner/owners :/