Mystery
Ignition
Noise Problem
My 1999 4.0 liter jeep Cherokee Sport had a very quiet
ignition system when it rolled out of the factory. No pulse
noise, no whines, or clicks, just nice and quiet. At the
50,000 mile point, the dealer said it was time to replace the
plugs, plug wires, distributor cap, and rotor. So, thinking
nothing of it I said go ahead and drank another cup of their
free coffee as they took care of it. A half hour later I
rolled out and the nightmare began. A couple miles down
the road I snapped on the 220mhz rig and was greeted with
horrendous ignition pulse noise on a local, full strap
repeater!!! Obviously thinking something was wrong, I
turned around and went back to the dealer and told them that
something they had done was fubar. They quickly rolled the
vehicle in and went through everything. Nothing was
cracked, unseated, or incorrectly installed. But the
pulse noise continued. Oddly, the AM broadcast band of
the vehicle radio did not seem to be affected, but the FM
broadcast band was. Very odd indeed. I grabbed the
old wires, plugs, distributor cap, and rotor and took them
home with me, figuring I could quickly get to the bottom of
this. Strange as it may seem, subbing the parts back out
did not resolve it. It was there and it was very
prevalent on the VHF bands. A shortwave radio 30 feet
away was easily overcome with the same noise when the engine
was running. Before this incident, I could put the
shortwave radio on the hood of the engine and it would not
hear any engine noise. All my body panel bonding straps
were tight, the exhaust system was still grounded at several
points, and my direct wiring to the battery connection block
was still good to go. All the normal methods of avoiding
these problems were applied and unchanged from the quiet days
prior to the "tune up". Soooo... where to go from
here??? I did some web research and found a company
called Magnecor. They make inductively wound ignition
cables with a ferrite core to resolve stubborn problems with
RF noise.
Magnecor
Ignition
Wire Company
I went ahead and ordered a pre-cut set of the KV85 CN
series wires for the Jeep 4.0 liter engine and waited for them
to arrive. Within a few days they were in my hands and I
hastily ripped out the Jeep/Chrysler carbon resistor wires and
installed the KV85 CN set. They looked great!
Although the wires are
1.5mm greater in diameter than the stock carbon wires,
they easily fit into the wire guides on the engine
block. Unlike carbon resistance wires, these wires
do not deteriorate over time, and have much less
resistance than the stock wires, resulting in a hotter
ignition system. The engine starts on 1/2 turn in
all weather, and runs great. However, the
nicest thing is that the engine is once again completely
RF silent on all bands. Problem solved! I have
no idea why the replacement wires and the old original
wires were so noisy, but the new Magnecor wires are
awesome. It is one of those mysteries that shows up
now and then, but I am glad I was able to resolve
it. The ignition wire kit cost about $65 and was
worth every penny.