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Author Topic: Ignition Noise in Honda Civic  (Read 1192 times)
W4QA
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« on: November 07, 2003, 10:58:33 AM »

Here is the latest update on my escapades with the '99 Honda Civic LX. After bonding the hood to the chassis in two places (bypassing the hinges), installing Magnecor RFI reducing plug wires, replacing the spark plugs, grounding the engine block, and bonding the exhaust pipe to the frame, I had reduced the ignition noise just a little bit. A slightly larger improvement resulted from installing a Larsen NMO type mount in the center of the roof and dispensing with the magnetic mount. I suspect I have managed to reduce the noise by 10dB or so by doing all of this.

Unfortunately, I *still* have ignition noise (even in FM mode) across the 2m spectrum. The popping noise is heard, in particular, when the engine is idling and lessens somewhat when going at a higher speed. I can hear the popping even when listening to a repeater that is s8 or s9. Again I have checked to see that the noise is "radiated noise" by using a handheld inside the vehicle -- the same noise is heard by the handheld, although it is not physically connected to the electrical system of the car.

Fan motor noise is another issue that I will tackle later, and I think I know how to take care of that. Its just a bit of an ordeal getting to the fan motor to bypass the power leads -- so I want to cure the ignition issue first.

Any ideas on what to do next? I am thinking of trying different plugs now (Autolite Resistor plugs instead of the 'standard' NGK plugs sold by Honda which I initially installed). Are there other components in the ignition system that may fail causing the kind of problems I am seeing?

Help is very much appreciated.

73,
Rush -- W4QA
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KD6KXT
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« Reply #1 on: November 28, 2003, 04:44:11 PM »

Hello Rush,
Here are a couple of suggestions that may be of help.

There is a "plastic" "dust shield" as Honda calls it that covers the ignition coil and igniter.  It fits below the rotor.  If this is missing ignition noise will result in the cars AM radio.  I have found that aftermarket caps, specifically Bosch, can also contribute to RFI.  Also check the connections on the ignition coil - phillips head screws- prone to corrosion, moisture seems to enter past a dried out cap gasket.  NGK or ND plugs are best in my experience.

Another suggestion is to check the battery ground.  Follow the brown ground wire from the negative terminal, it makes a connection to the chassis below the battery which is susceptible to corrosion, especially if the battery is overfilled.  This gound wire also makes a connection to the transmission.  I've found it loose or not connected, especially on a manual transmission if the clutch has recently been changed.  There is also a ground wire from the chassis, behind and above the left headlight, that attaches to the valve cover or power steering bracket.  It also wouldn't hurt to check the ground connection at the thermostat housing - follow the lower radiator hose to the engine.

Good Luck
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WB1AEX
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« Reply #2 on: February 28, 2004, 05:22:39 PM »

I recently went through this nightmare with VHF/UHF suppression after a 50k tune-up was done on my '99 Jeep.  Noise was never a problem with my VHF/UHF equipment before the plugs, wires, rotor, and distributor cap were replaced by my dealer.  Following the tune-up, I heard strong ignition noise popping away on full scale repeaters.  I replaced the plugs (Champion suppressor equipped) with Autolite Resistor types, and the Mopar ignition wiring with Autolite Professional Series Suppression wiring.  Things seemed a little worse!  I then found the problem.  The distributor cap the dealer had installed during the tune-up was a cheap carbon button aluminum contact cap.  I replaced the rotor they installed and then the cap, with a brass fitting cap that uses a spring loaded brass bushing in the center and the noise was almost back to nothing.  I could still hear a bit of popping when accelerating, on moderate signals. I then went back to the Mopar wiring (it had twice the resistance per foot compared to the Autolite wire) and the noise dropped even further.  I finally went back to the Champion plugs and the noise dropped to close to zero, being heard only now and then on the very weakest signals.  I found the last step curious due to the fact that Champion seems to get very little respect from the automotive crowd.  From an RFI standpoint though, the Champion plugs use a solid state supressor rather than a carbon resistor, and it appears to do a much more thorough job of suppressing ignition noise.

I hope you are able to resolve your problem.  There is nothing worse than listening to ignition noise on a strong FM signal.

Good luck,

Rob  WB1AEX
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