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99 Cherokee Sport 4.0 Liter Ignition Suppression Question

Hi,

My trusty '99 Cherokee Sport 4.0 liter just went in for a 50k checkup. The dealer put in a new set of plugs, a new distributor cap/rotor, and a new sparkplug wire set as part of the normal maintenance. The vehicle runs great, but I now have impulse ignition noise in my FM 2 way equipment (220 mhz) that I did not have before. The new plugs are Champion RC12ECC (resistor suppressor) and the new ingition wiring is Mopar (Ignition suppressor wires) so I am puzzled. I never had any ignition noise issues with the OEM stuff for the first 50k miles, but now, even with portable equipment 10 feet away from the vehicle, I can hear fairly strong impulse noise.

I checked all the wiring to assure that everything was seated correctly and nothing looks out of place.

Does anyone know if the stuff they put in is more poorly suppressed than what was installed originally by Chrysler? Has anyone had better luck with different brands of plugs or wire sets? I'm just looking for a little input before I discuss the issue with my dealer.

Thanks,

Ender

"The only thing necessary for the triumph of evil is for good men to do nothing." Edmund Burke

Reply to
Ender
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nothing." Edmund Burke

Reply to
L.W.(ßill)

Thank you for your response.

That is another oddity about this problem, which I failed to mention. There is no ignition pulse noise on the AM radio, even in the absence of a signal or with a distant station. Broadcast FM is not a problem either. The problem is very pronounced, however, above 150 mhz, and is easily detected from 10 feet away with a 220 mzh HT, as well as with the onboard 220mhz equipment. This is a real mystery to me as I would have suspected that the cowl mount antenna right by the engine compartment as well as the lower frequency of the broadcast band (and the nature of the AM detector) would have been most susceptible.

Regards,

Ender

"The only thing necessary for the triumph of evil is for good men to do nothing." Edmund Burke

Reply to
Ender

nothing." Edmund Burke

Just in case anyone else runs into this problem, I did finally find the solution to the massive ignition noise problem on my 220 mhz radio equipment.

After replacing the Champion plugs with Autolite Resistor plugs, and the Mopar ignition wiring with Autolite Professional Suppression wires and getting no improvement, I moved on to the distributor cap and rotor.

It turned out to be the replacement distributor cap and rotor that my dealer installed during my tune up. It had all aluminum fittings and used a carbon button to transfer spark from the ignition coil to the rotor inside the cap. While this caused absolutely no noise on the AM/FM broadcast bands, it absolutely ripped up the vhf/uhf bands on my ham gear with spark noise. There was nothing wrong with the replacement cap and rotor, no cracks or loose hardware, and the engine ran perfectly with these "noisy" tune up parts. I replaced the cap and rotor installed by my 5 star dealer with "Standard" brand brass fitted replacements (from Acme Auto) and the problem was instantly resolved. The "quiet" distributor cap has the brass spring-loaded button that makes contact with the rotor, which is also brass. It is absolutely silent on the vhf/uhf bands.

Hope this helps anyone who runs into this issue.

Regards,

Ender

"The only thing necessary for the triumph of evil is for good men to do nothing." Edmund Burke

Reply to
Ender

Good to know, thanks for the follow up!

Those 'white metal' distributor cap posts are cheap crap.

The 'good' ones are the 'old style' brass ones. Those can even be cleaned once or twice with success. The white metal ones will arc out almost instantly if you clean the posts.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Ender wrote:

nothing." Edmund Burke

nothing." Edmund Burke

Reply to
Mike Romain

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