Ignition noise

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I would appreciate any suggestions to solve a long time problem with ignition noise on the radio of my rust free 87 Mercury Cougar. I believe it is ignition since it is only on AM and is a popping noise (not whine) which changes with engine speed. I have tried the following:
Subsituted the radio with a known good radio from another 87. Noise still present.
Removed and cleaned up antenna/mount assembly. Continuity tests of the antenna and cable assembly end to end are perfect and at specs.
Cleaned up all ground connections which are scattered throughout the vehicle, inside and out.
Ran a ground wire from radio chassis to known good ground point.
Replaced plugs with OEM resistor, plug wires (motorcraft), cap, rotor and coil. No change.
I even tried installing a couple ferrite units from my computer stuff around the radio harnesses which made no difference.
I know vehicles usually have some kind of noise filtering capacitor bolted to the chassis somewhere but I looked everywhere and do not see one. I was considering installing one off the radio power connection.

Kind of stumped and would appreciate any suggestions. I want to keep the original radio in the car.
 
N/M. Reading comprehension issue
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So in my home stuff I will get noises similar to these when I have ground issues. You should make sure the unit has a good ground. You could also try a ground loop isolator. I'm sure they have them automotive style
 
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I just solved this type of problem on my Toyota pickup when I installed a CB radio. Yes the popping sound is ignition noise.

Installed a new 8 gauge ground wire from chassis to battery. Wrapped new hot and ground wires around a Toroid Core FT240-31 Ferrite about eight times. My CB radio does have a noise blanker which helps with ignition noise.

After running new ground wire, and running new wires straight from battery to radio, I could not hear the ignition noise, but could still see it on the receive meter with a press of the gas pedal. I think the noise blanker of CB radio was suppressing the noise. After the toroid core was installed, no noise and no movement on the meter. Not sure if it will help your problem, but it did the trick for me.

You could try a Navone Engineering passive noise filter N-25. They also have a more expensive active noise filter.

http://davidnavone.com/filters-noise-suppressors/

The type of toroid I used can be purchased from kf7p for $7.95 free shipping.

Ferrite toroid, mix 31

Dimensions:

Length 0.5"

OD 2.4"

ID 1.4"

http://kf7p.com/KF7P/Ferrite_chokes.html
 
Does the Distributer have a fresh supressor condensor on the "+" terminal of the coil? If not There is your cause. Make sure the cap is
good.

Now If it's RF cast and received then you have to find the source.( see above) You can poke around with a AM pocket radio, but another likely place is the rotor arm - if its a buss bar rather than a potted supressor resistor.

But you still have arcing at the coil towers and dist caps are not typically RF suppressing.

I get ignition noise but only on bottom and top of the band .

Is your noise all over even on a strong received frequency?

Good luck with this
 
Originally Posted by Lubener
I believe it is ignition since it is only on AM and is a popping noise (not whine) which changes with engine speed.


Are there people that still listen to AM?
 
Yes we have a few well managed great stations for all day news /traffic/weather and sports and good afternoon talk.

WBZ 1030 and WRKO 680 are two of them.

What is there to listen to on FM? Around here all garbage except one 1/2 decent Classical station 99.5 WCRB

I've heard the same rotating rock playlist a zillion times over the past 50 years.

Used to be a couple good college album stations but they are gone I guess.
 
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Yes but when you are old and cant hear above 6Khz the the difference is less.

And WBZ 1030 AM is a very professional, tightly run ship - which is mostly non-existent these days.

I don't have a FM news traffic and weather AFAIK.'

Unless its on The Shark 105.3 FM - but too moronic to tolerate.
 
One thing that almost all cars used to have and no one has mentioned, installing a ground (wire) from you hood to the firewall may help.
 
Originally Posted by ffhdriver
One thing that almost all cars used to have and no one has mentioned, installing a ground (wire) from you hood to the firewall may help.

I have two "spring" leafs mounted on each side of the firewall and the other ends touch the hood when closed. I cleaned these up when I was troubleshooting.
 
Originally Posted by atikovi
Originally Posted by Lubener
I believe it is ignition since it is only on AM and is a popping noise (not whine) which changes with engine speed.


Are there people that still listen to AM?

I am one of the few who still appreciate the non sense on AM and cannot stand to listen to the terrible music on FM Cleveland radio. I hate technology and prefer to avoid it so my brain doesn't go soft..
 
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