akasnajo

My Jeep generates a tone at 2200 rpm when under load (accelerating only).
I've ruled out the stereo, amps, speakers, the gauge cluster, and the door chime by removing them electrically (or physically) with no change to the tone.

The problem started after I replaced my main electrical cables with 4 gauge wire.
The following was installed:
B+ to Starter
B+ to Distribution (Fuse Box)
B- to Engine Block
Block to Firewall (ground)
Alternator Case to B-
B- to Fender (main body ground)
Alternator to Distribution
150 Amp ANL Fuse

Troubleshooting steps taken:
1. Disconnected power to amps and head unit (no change)
2. Disconnected speakers from amps. (no change)
3. Pulled speaker wire out of the driver-side under door wire channel (noise reduced)
4. Pulled all speaker wire out of vehicle (noise further reduced)
5. Cut/pulled wires from all speakers (no change from 4)
6. Removed warning chime module (no change)
7. Removed gauge cluster (no change)
8. Removed fuse at the battery side of the audio power cable (no change)

I've checked all the new wires to make sure they are connected properly. They've been installed since July. I've had some health problems so I've dealt with the noise by avoiding the 2200-2300 RPM range and/or by turning up the sound system to drown it out. I figure with thousands of dollars and hundreds of hours, I owe it to myself to solve this one.

I'm going to pull the fuse from the stereo power wire in the engine bay to see if I'm getting inducted noise from the B+ to Distribution into that cable and thus the rest of the vehicle. They run right next to one another for 18" or so.

I'm not sure what to do next. Replace PCM? Replace Alternator? Install a huge-*** cap someplace? Pull relays? It's super hard to identify the location of the noise because it only happens under load at 2200 - 2300 rpm.

Any advice would be appreciated. I'll post updates as I learn more.

akasnajo

Tomorrow I'm going to take a look at the engine wiring. Maybe there's something stupid going on that I missed. After that, I'll see about replacing the ECU and the alternator.

akasnajo

Could this be vacuum related? It really sounds electrical because it's a constant sounding tone. I would expect vacuum sounds to vary.

Is there anything that our engines do at 2200rpm (or there-abouts) that they don't do at other rpms?