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A parade of symptoms, need help

Old 09-04-2015, 04:27 PM
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A parade of symptoms, need help

Hello everyone, I've been dreaming for an rx8 for years, I've went trough countless posts here, I am now an owner of a 2003 (231) MT from 2 weeks.

My Story
I both it used with 114K km and a flashing cel (misfire)

I drove it a bit, car was running full power.

200 KM laters it started having weird rattles, and started loosing power after about 10-15 mins of driving. Oil light came (newby), added oil, ran a bit better.

A few drives later it started rattling again and loosing power when hot. I changed Spark Plugs with NGK 8-L & 9-T's.

Flashing CEL continued but car was running like new for another 300 KM on a long, hot drive.

Filled a full tank of 95 octane fuel (low quality, compared to 100 octane) and the car instantly lost a bit of power, say 1/4

I continued highway driving until the point where I could barely keep 100 km/h. Oil light came, I stopped for 5 mins, check, it was full (I didn't overfill it the list time I added oil ). I continued on with huge power loss and rattling even at 4k rpm. Had to push it hard just for stop & go traffic, but it barely got to 4k rpm.

Replaced fuel with 100 octane, didn't solve the problem. Car became sluggish even on short drives.
I installed new NGK Coils, NGK Wires and I already had NGK spark plugs. Cleaned K&N Filter, did not over oil it but there was a lot of oil in the rubbery accordion thingy after the air filter.

In the end...

My ignition is new (wired properly),
my battery is new,
oil level is good 5W30,
the car has it's CAT removed.
It starts within a single second (hot and cold)

When warm:
1. Power is about 3/4,
2. normal idle,
3. misfires above 5k rpm

When HOT:
1. Power is about 2/4,
2. idle below normal, but stable,
3. misfire consistently,
4. makes rattling noises between 4-6k rpm.
5. throttle response: giving it 20% throttle and 100% throttle barely makes a difference! I can feel the engine is under more load, but the power output is the same. It even feels like it is choking when giving lots of gas, as makes more power when I let off the throttle.
6. the A/C - makes idle rougher, more vibrations.
Also keeping the car at 3k RPMS with A/C On makes a weird issue - every 10 seconds it spikes a bit (100 rpm) and drops down about 400 rpm for 3 seconds, than goes back to 3000 rpm.

On my list...
Clean MAF
Get Flash MSP16
Ask for Heater hose for M.I.A.C.
Check compression (altho it starts instantly)
Check fuel pump pressure
Premix with 2-stroke
Your suggestions...

I have been searching & researching here since before I got it. Any help would be greatly appreciated! Rev on!
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Old 09-05-2015, 11:42 PM
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I would check the fuel pressure first...sounds like it could be a dying fuel pump

What are your ST and FLFT's? Do you have any CEL's? other than the flashing ones?
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Old 09-18-2015, 11:14 AM
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Thanks for your suggestion dannobre, I did check the fuel pressure after an average drive when power was about 1/2. The pressure indicates ~2 Bars, but it should be at ~4 bars (58psi).

The car was diagnosed and it did show an issue with the fuel pump, nothing specific. I did change the filter inside the pump but it did not help.

The car runs superb a few minutes after taking off with about full power. But the more I drive it, the worse it becomes.

The weird thing for me is heat. A hard drive at night is 1/2 of power lost. A soft drive in hot weather is more than 3/4 of power lost. How can the Fuel pump be influenced by heat when it is inside the tank?

Is it possible for the Fuel Pump to overheat and reduce pressure?
Recently O2 sensor CEL's popped up P0037 & P0139 (don't know if they are related).

My question is: Should I replace the whole fuel pump assembly? Should I replace only the pump with something like walbro? Can the fuel pressure regulator be faulty and restrict fuel flow in hot weather? Any ideas?

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Old 09-18-2015, 12:11 PM
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You might want to get it on a lift to check the catback exhaust to be sure there are no old chunks of cat strata blocking the pipe or muffler.
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Old 09-21-2015, 06:36 PM
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A flashing CEL is always a misfire.

Fuel pumps on series 1 RX8's are prone to overheating and shutting off as they age, and especially if the fuel level is low in the tank (this uncovers the pump and takes away the cooling of the pump by the fuel) The best option is to replace the entire fuel pump assembly, if that is the issue.

Starting the Engine
• Starter
• Battery
• Engine Compression
• Grounding Wires
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Fuel Pump
• Fuel Injectors

Generating Power at Full Throttle
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Engine Compression
• E-Shaft Sensor (ESS)
• Air Filter
• Intake Valving
• Throttle Body
• Mass Air Flow Sensor (MAF)
• Fuel Pump
• Fuel Injectors
• Catalytic Converter (Cat)

Keeping the Engine at a Cruise
• Ignition Coils
• Spark Plugs
• Spark Plug Wires
• Engine Compression
• E-Shaft Sensor (ESS)
• Intake Valving
• Throttle Body
• Mass Air Flow Sensor (MAF)
• Fuel Pump
• Fuel Injectors
• Front O2 sensor
• Catalytic Converter (Cat)

RX8 Club’s recommended maintenance schedule, more comprehensive and proactive than Mazda’s schedule.
30,000 miles:
- Replace Ignition coils
- Replace Plug wires
- Replace Spark plugs
- Clean MAF (mass air flow sensor)
- Clean ESS (e-shaft sensor)
- Reset ESS profile
- Clean power steering connections
- Clean battery terminals and clamps
- Replace transmission fluid
- Replace coolant (Mazda FL-22 is highly recommended)
- Replace air filter
- Replace brake fluid (fluid in the brake lines AND the clutch line)
~$300 USD in parts if you shop smartly.

every 60,000:
...all 30,000, plus...
- Clean all chassis electrical grounding points
- Replace accessory belts
- Clean OMP lines
- Replace rear differential fluid
- Replace thermostat
- Clean / Straighten AC condenser fins
- Clean / Straighten oil cooler fins
- Inspect catalytic converter
- Clean / Inspect intake valving
- Consider / inspect all points in 90,000+ as well, many items fail early
~$130 USD in parts if you shop smartly.

...all 30,000, plus any 60,000 not yet done, plus...
- Replace coolant bottle
- Replace radiator hoses
- Replace radiator
- Replace front O2 sensor
- Replace motor mounts
- Inspect clutch pedal assembly for flex / weld breaks
~$900 USD in parts if you shop smartly.
At 100k, anything original in the cooling system is really suspect and failure prone. It represents the biggest threat to your engine.

Last edited by gwilliams6; 09-21-2015 at 06:39 PM.
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Old 09-22-2015, 06:36 PM
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Thanks for the response.

Misfire is gone after i cleaned MAF sensor (should have done that before I changed the whole ignition system)

I'm changing the fuel pump with the assembly tomorrow. I hope it's not an electric issue with wires overheating.
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