The Back Story
The Mazda RX-8 entered the market with a lot of hype, hope, and enthusiasm. Unfortunately it left the market with little attention due to disappointing sales and a bad reputation. This bad reputation means some RX-8s are pronounced dead too quickly, when there may actually be a fixable problem.
This is a shame, as the chassis is a very capable one. The overall chassis design itself was basically shortened and then duplicated to create the third generation of the Miata (2006-2015). You know if the overall layout of the car is good enough for a Miata, then the handling it provides must be pretty respectable.
The problems with the RX-8 lay in trying to update Mazda's13b engine for modern emissions standards. With close to 10 years of development time between when the RX-7 left the U.S. market and when the RX-8 arrived, there were lots of changes made to the 13B design that all addressed power, fuel efficiency, and reliability. Considering Mazda was the only company applying research and development into the rotary engine, the performance increases over the older rotary engines of the past were impressive. It sounds like winning situation, but it wasn't to be.
Hamstrung by tighter emissions regulations, the new redesign did not live up to the expected performance numbers. Using a turbocharged system like the previous 13B-REW seemed to also be off the table due to newer emissions standards. Nevertheless, owners of the manual transmission, high output model RX-8 found themselves with an agile, responsive, fun to drive car making approximately 240-250hp. Not as bad as many have come to believe as years went by.
Achieving better torque and horse power than previously naturally aspirated rotaries meant changing the design of the intake and exhaust ports on the engine, and designing a radically advanced intake manifold system to change air flow characteristics at different engine speeds. Using several systems of valves and runners in the intake system helped the new engine achieve optimized air flow for optimized power at all engine speeds, similar to how piston engines use variable valve timing to achieve the same performance goals. This complicated system of valves and actuators controlled by the vehicle's computer can sometimes cause running issues that can lead an owner to believe they have a bad engine.
The Project
This particular RX-8 arrived with a recently rebuilt engine and complaints of being unable to rev the engine beyond 7,000-7,500rpm without experiencing hesitation and power loss along with a check engine light. While red-line for the car is indicated at 8,000, the engines easily rev to 9,000rpm. Either way, it should not stop at 7.
Investigating the car's stored engine code revealed a code for voltage too high on one of the intake manifold runner circuits, along with engine codes associated with the running issues this caused. Without that advanced intake system working properly the power simply won't be there when you need it, and a rotary that doesn't rev to the sky is no rotary at all. Time to get started.
The Mazda RX-8 entered the market with a lot of hype, hope, and enthusiasm. Unfortunately it left the market with little attention due to disappointing sales and a bad reputation. This bad reputation means some RX-8s are pronounced dead too quickly, when there may actually be a fixable problem.
This is a shame, as the chassis is a very capable one. The overall chassis design itself was basically shortened and then duplicated to create the third generation of the Miata (2006-2015). You know if the overall layout of the car is good enough for a Miata, then the handling it provides must be pretty respectable.
The problems with the RX-8 lay in trying to update Mazda's13b engine for modern emissions standards. With close to 10 years of development time between when the RX-7 left the U.S. market and when the RX-8 arrived, there were lots of changes made to the 13B design that all addressed power, fuel efficiency, and reliability. Considering Mazda was the only company applying research and development into the rotary engine, the performance increases over the older rotary engines of the past were impressive. It sounds like winning situation, but it wasn't to be.
Hamstrung by tighter emissions regulations, the new redesign did not live up to the expected performance numbers. Using a turbocharged system like the previous 13B-REW seemed to also be off the table due to newer emissions standards. Nevertheless, owners of the manual transmission, high output model RX-8 found themselves with an agile, responsive, fun to drive car making approximately 240-250hp. Not as bad as many have come to believe as years went by.
Achieving better torque and horse power than previously naturally aspirated rotaries meant changing the design of the intake and exhaust ports on the engine, and designing a radically advanced intake manifold system to change air flow characteristics at different engine speeds. Using several systems of valves and runners in the intake system helped the new engine achieve optimized air flow for optimized power at all engine speeds, similar to how piston engines use variable valve timing to achieve the same performance goals. This complicated system of valves and actuators controlled by the vehicle's computer can sometimes cause running issues that can lead an owner to believe they have a bad engine.
The Project
This particular RX-8 arrived with a recently rebuilt engine and complaints of being unable to rev the engine beyond 7,000-7,500rpm without experiencing hesitation and power loss along with a check engine light. While red-line for the car is indicated at 8,000, the engines easily rev to 9,000rpm. Either way, it should not stop at 7.
Investigating the car's stored engine code revealed a code for voltage too high on one of the intake manifold runner circuits, along with engine codes associated with the running issues this caused. Without that advanced intake system working properly the power simply won't be there when you need it, and a rotary that doesn't rev to the sky is no rotary at all. Time to get started.
The code could be cleared, and would not return until you once again attempted to take the engine over 7k rpm. Almost every time the code was reset, it would return as the same P2010, although it did show up as a code P2004. Since these codes are associated with the APV system, one of the valve systems in the intake manifold, testing began there.
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This system uses a geared electronic motor to turn two valves in the manifold. Bench testing the motor directly found it to operate when power was applied. Turning the corresponding gear on the intake manifold showed the gear could be moved easily, indicating that the actual valves were not stuck due to carbon and corrosion. This can happen to RX-8's that don't get run in the upper RPM range as often as they should. Similar problems can occur to piston engine cars that also don't see higher RPMs on occasion.
Still, testing indicated that the motor, and actual valves both appeared to be working. This left wiring to the motor and the PCM as culprits. The wiring was tested, and found to provide proper power and ground to the motor. The three signal wires that run from the motor to the PCM were also tested and found to have good continuity. |
That left the PCM. Replacing a PCM for this sort of failure is highly unusual, and not cheap. Modern PCMs are complicated, and require reflashing/special programming when installed into cars that also comes with its own cost. Analyzing the situation further, it was thought that the APV motor could still have a short. While the motor could be made to run by applying power and ground to it directly, there was a chance that the fault lay somewhere in how it accepted input from one of the three signal wires coming from the PCM. While the wires them selves tested good, it was possible that a short in the motor could make it unable to accept input from the PCM while still operate during bench testing.
A new motor was installed, and the problem persisted. During the testing of this system, other codes relating to the other intake runner systems in the air intake would occasionally show up. The SSV (secondary shutter valve) and VDI (variable dynamic intake) systems, respectively. While it remained unlikely, it was elected to test the actuators and solenoids for both of these systems on the possibility that they could be the problem.
A new motor was installed, and the problem persisted. During the testing of this system, other codes relating to the other intake runner systems in the air intake would occasionally show up. The SSV (secondary shutter valve) and VDI (variable dynamic intake) systems, respectively. While it remained unlikely, it was elected to test the actuators and solenoids for both of these systems on the possibility that they could be the problem.
So, it looks like it's time for a recap of the situation.
With every other avenue of repair exhausted and thoroughly tested, the only possible component left was the PCM. At this point the car was passed over to a local Mazda dealership with the correct software to install and program the a new ECU to communicate with all the other electronic modules installed on this vehicle. Even with the right ECU, with out that programming, the car wouldn't work.
While this situation turned out to have the most unlikely of failures (the PCM), and needed to go to a dealership for the final step in the process, it's not at all uncommon for the running issues being experienced to occur because of the other electronic components mentioned. That's important to remember since so many RX-8s are thought to have a bad motor when it can actually be something else.
With the right repair this RX-8 became a great driving car again. If your RX-8 is suffering from a similar issue give us a call to look it over before giving up on it.
While this situation turned out to have the most unlikely of failures (the PCM), and needed to go to a dealership for the final step in the process, it's not at all uncommon for the running issues being experienced to occur because of the other electronic components mentioned. That's important to remember since so many RX-8s are thought to have a bad motor when it can actually be something else.
With the right repair this RX-8 became a great driving car again. If your RX-8 is suffering from a similar issue give us a call to look it over before giving up on it.