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FIXED - 2001 MR-2 Spyder
Issue:
Very rough idle. Engine rocks back and forth, then shuts off after about a minute if you don't throttle to keep the RPMs high. Car drives, but power is lacking. It feels like you're in too high a gear when trying to give it power. The engine stumbles when you try to throttle hard.

OTHER DETAILS:
OBDII codes: P0300 P0301 P0302 P0304

All ignition coils replaced.
(improves performance momentarily, and may rotate the engine codes, but doesn't permanently solve the problem. The code just jumps around, indicating misfires on different cylinders)
All spark plugs replaced with NGK Iridiums.
2 sets of O2 sensors burned out and had to be replaced.
Checked catalytic converter. Surprise, guys. It was empty. All the honeycombs had been burned out.
Replaced catalytic converter. Didn't solve the problem. 1 more O2 sensor burned out after that. Replaced. 1 more Catalytic converter was blasted out. Replaced.
MAF sensor checked. No issue. Changed it anyway. Checked for vacuum leaks in the intake manifold. None. Passed compression test. Changed valve cover gasket to ensure proper seal anyway. Checked fuel pump. Pressure is consistent.

Transmission was replaced at 110k miles.
Engine was rebuilt at 90k miles.
Car currently has 124k miles.
No crank sensor issues.
Timing is fine.
Belts are new.
No exhaust leaks

SO WHAT WAS THE PROBLEM?
The fuel injectors

These were the original injectors that were in place since 2001. I changed them out with some OEM remanufactured injectors and now the car runs perfect. All the power I dearly missed having is back.

The injectors couldn't deliver consistent fuel, so they would cause the engine to idle rough.
But under throttle, they would deliver inconsistent quantities of fuel to each cylinder, which would exhaust unburnt fuel out of the cylinder and launch a fireball through the exhaust system, destroying o2 sensors consistently and blasting out the catalytic converter.

This is also why the issue looked like a timing or ignition issue because of all the misfires, when really it was a fuel delivery issue. The electronics were firing at the right time, but the amount of fuel being delivered was completely at the mercy of the old injectors.

A fuel injector problem doesn't necessarily show up on a fuel pressure test, which makes sense, since there's nothing wrong with the fuel pump.

Was this the only issue? Doubtful. But since almost every peripheral has been changed out at some point, it would be difficult to pinpoint any other trigger points retrospectively.

Hopefully this analysis helps out someone who may be having similar issues with their vehicle.

- Demi
 
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