Radio noise

For the last couple of years, I've had static on the FM stations on the radio. Frequency directly related to engine RPMs.

As near as I can tell, the block ground is good.

It's done this with 2 different radios, and the current deck is grounded back to the battery (also has a noise filter on the 20A positive lead.)

After I got back from Moab, the noise had mysteriously disappeared. And the distributor bushings started squeaking. I put in a new distributor today, along with a new set of Mopar Performance plug wires. BTW, plugs are Champion Truck plugs, new a year ago. After putting in the new distributor and wires, the FM noise is back.

As near as I can tell, it's got to have something to do with the distributor.

Any suggestions?

Radio noise can sometimes be cured by switching to resistor-type spark plugs. Also, a bad plug wire, cap, or plug can cause radio noise.
Make sure the antenna cable is well grounded at the antenna base as well.

Concur, antenna ground or antenna cable connector loose/wire broken, on the passengers side interior.
Eagle recommended grounding the battery to the front clip, removed most of my FM radio noise. Tightening a loose antenna base took care of the rest. Cleaning the motor to firewall ground, also helped some (sure made the motor run better).
Found a broken middle wire on the interior passenger side antenna connector on one XJ. Poor reception/noise. Antenna wire was hanging and the passenger often stomped on it.
Had one antenna (retractable) that wasn´t making good contact (poor reception/noise), the base of the antenna was corroded, simple Ohm test from the antenna, to the middle wire, tipped me something wasn´t making good contact. Broken wire or poor contact seems to be, where much of the random noise gets in the system or overpowers the filters.
I´ve had bad experiences with aftermarket condensors and filters for the ignition system.
I´ve had amatuer radios and CB´s in all of my rides, over the years. Random noise is an old foe.
Filters are an iffy thing. They only filter certain noise (freq´s), not all.

Radios can pick up ignition noise three ways: through the power cables, the antenna, or the radio case.

The radio case is the least likely, they are made better these days, but grounding it and putting a grounded foil blanket on the inside of the case top helps cure that.

The power cables are the most likely culprit and the easiest to cure. Filters are available, get a beefy one with a big capacitor.

The antenna is the tough one. If this is the problem, then I agree that filters on the antenna leads probably won't help much. You can tell if your antenna is the problem by determining whether it is just your vehicle that causes noise or whether it happens when other vehicles (esp. older ones) are next to yours. If that is the case, try getting one of the short loaded coil antennas and ground it well. Otherwise, try re-routing the lead and wrapping it with a grounded twisted-pair cable.

hth

Whine or pop type of noise? Whine is a ground loop...make sure you grounds are good. Sounds more like you have a pop, a few thing mentioned will help, sence the noise returned after you worked on the wire, cap etc. I would look at resistor plugs, and make sure you used spiral wrapped wires to help with the EMI.


Rev

It's a pop noise. Frequency is directly related to engine RPM.

The radio has a dedicated 20A positive with a filter already. Also, it's grounded back to the battery.

The noise has actually persisted through multiple plugs (both Bosch Platinum and Champion Truck,) wires (Autozone and Mopar Performance), caps (Autozone and Mopar) and radios (both Alpines.)

The really odd thing is that the noise had disappeared after I returned from Moab. And reappeared with the new distributor, cap, rotor and plug wires this weekend.

I may just replace the coil on general principles. It is the original coil.

Lemme guess....popping only on the radio...not tape/CD, right? If so you are picking up ign. noise. This noise has to start somewhere in the secondary ign. system. pull 1 wire at a time off distributer and see which wire is doing it? If you need help....I am in Plainfield...would be willing to try to help.

Rev

Rev Den said:

Lemme guess....popping only on the radio...not tape/CD, right? If so you are picking up ign. noise. This noise has to start somewhere in the secondary ign. system. pull 1 wire at a time off distributer and see which wire is doing it? If you need help....I am in Plainfield...would be willing to try to help.

Rev

Click to expand...

Yup, just FM radio. AM radio works fine, as does the CD.

I'm a dumba$$.... should have though of pulling a single wire at a time. That'll show if it's a single wire or plug. I kind of doubt it, as the problem has persisted through a complete change of hardware downstream from the coil.

New ignition coil today.

No more noise.

ChiXJeff

ChiXJeff said:

New ignition coil today.

No more noise.

ChiXJeff

Click to expand...

When you really think about it.. you either had a private jamming transmitter or.... your XJ was alive and was trying to tell you something

Btw, some might find this of interest... and this