I never finished my write-up for pulling the motor on this Mazda, but I did finish the job. Well, I'm about to just gotta order and install the new cat.

I want to list some faults and fixes here because this was an interesting one for me. Focusing on the thread title fault. The star of the show is the "Radio Interference Capacitor."

When this car came to me it had bad exhaust leaks from both exhaust manifolds, professionally diagnosed with only snapped studs.



Think I'll make these into a commemorative keychain


It felt under-powered when driving and sounded like a lawn mower, so I tended to that first. Along the way I repaired all the oil, vacuum, and trans fluid leaks. It sat for 4 months while I screwed with it in our carport. When it was all done and assembled I took it for a drive and it idled rough (rev followed by lull), ran like garbage, shifted hard and erratically, overheated after 30 minutes, and couldn't exceed 40mph. It also had an intermittent, flickering low oil light at idle. Also, when electronics were turned on, or the engine revved, all the gauges in the dashboard would sometimes sweep. Full gas, overheating, full battery, going 120mph at redline rpms. Then go back to normal.

The more times I started the car to test it, the worse the idle got, and the more the gauges swept, as if the car was learning to run worse. They started sweeping every time I pressed the gas. When they swept, acceleration would cut out. I had to push the car back up the driveway numerous times.

Had a mobile mechanic come out for a second opinion. He suggested the catalytic converters were bad. This turned out to be correct. Front right was so clogged that it was causing a sort of limp mode as well as the overheating. My scanners picked up that the exhaust was failing but didn't list any faults. Likely caused by being driven extensively with the significant manifold leaks.
Regarding the electrical issue he pointed to the Range Sensor. If not the Range Sensor, the PCM. That part was not correct, but it gave much needed direction.

I replaced both the range sensor and the PCM and the fault went away, only to come back two days later.
At this point I started stripping wrap off the wiring harness in areas that looked ragged or re-done. All fuses were tested, as well as relevant relays swapped. I was working from the shop service manual, but couldn't run their fancy computerized tests. Well anyways.. It appears the indetectable fault was caused by the absence of the radio interference capacitor. It somehow affects interference generated, if my internet sources are accurate, by the ignition coils. The interference caused the PCM Communication Failure code detected by the mobile mechanic's snap on scanner, which neither my Innova or the Torque app could pick up. It coincided with the fault being triggered by the gas pedal.

The part cost $18.19 with tax from Ford.
Part #: F6AZ 18801A
Description: CAPACITOR ASY - RA
If your Mazda (or Ford Escape) has a suspect PCM, but nothing inside the PCM's casing is burned or discolored, consider this. I haven't yet found anything about it in the service manual regarding testing or faults, just a step for taking it off when disassembling the engine.

To whoever sold my neighbor this car, thanks for the challenge! I learned a lot.

Replaced: Gaskets

• valve covers
• upper and lower intake manifold
• timing cover
• oil pan
• throttle body
• front crankshaft
• cv shafts
• iacv
• all exhaust

Replaced Parts:

• rf headlight assy.
• oil pressure sensor
• lower control arms
• anti roll bar end links
• spark plugs
• pcv valve
• air filter
• battery
• thermostat
• belts
• atf cooler lines
• fuel filter
• oil filter
• pcv hose connections
• front right (against the firewall) cat converter

Cleaned Parts:

• throttle body
• egr
• iacv
• injectors
• all electrical grounds in engine bay
• cooling system

- Pyts