Spark plug noise on AM - suddenly

[Pablo]

1996 Volvo - runs like a champ.

Suddenly yesterday morning noise like heck on the low band AM. Follows RPM, an audible tachometer. Never had this issue before.

Figure it's high voltage spark side.

Checked the wires, etc all looked fine. Cleaned the wires. Didn't pull the NGK's or check the inside of the cap. No help.

Any clues?

 

[Terry]

Immediately sell 96 Volvo...

Check for crack or moisture in dist cap. Then inspect alternator, battery, electrical connections of same.

Remain calm.... Cheers TD

 

[Papa Bear]

Actually look for an antenna problem also. When the radio isn't getting a good signal, it's AGC (automatic gain control) will raise the gain of the radio's front end and I.F. circuit and it will be far more prone to interference.
Let us know what you find.

 

[Drew99GT]

Could be the ground wire for the radio. Mine did the same and tightening up the antenna wire and the ground for the radio got rid of it.

http://www.installdr.com/TechDocs/999501.pdf

 

[tom slick]

I've had an alternator make RF noise too.

 

[Pablo]

It's not RF, real and pure spark noise.

Good ideas.

I'll also do the lights off stray spark test tonight.

 

[Rickey]

Assuming the antenna is mounted on a metal surface:the ground connection from the coax shield to the body at the base of the antenna is also suspect. Does it sound as if its one plug circuit or all of them? One plug is pop-pop-pop etc. all of them sounds more like buzzzz and both as noted are affected by rpm. Buzzzz is usually grounding problem at radio,antenna,engine,etc. Pop-pop is usually broken (internally)plug wire and can be checked for with an ohmmeter,infinity or near infinity resistance equals bad wire. Also the antenna plug at the back of the radio should be checked for thightness. A cheap AM pocket radio can sometimes be used as a proximity detector for locating the noise. Is the problem affected when going over bumps? Good luck sir.
Rickey

 

[Papa Bear]

Who listens to AM anyway ??

 

[The Critic]

Quote:

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Who listens to AM anyway ??

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Werd. AM radio is ancient. XM Satellite Radio is the best!

Pablo, if such was to happen to my car, I'd immediately replace all suspected components: plugs, wires, rotor, and cap and not even think twice about it.

 

[brianl703]

I remember listening to top 40 on AM. And I'm not that old...that was in the 80s.

 

[michaelc80]

Quote:

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Quote:

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Who listens to AM anyway ??

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Werd. AM radio is ancient. XM Satellite Radio is the best!

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Weird. I can't see paying for something when I can get it for free elsewhere. If I want specific music I can always put in a CD, or run the MP3 player on my phone through the car radio.

 

[toocrazy2yoo]

I have the XM, it's invaluable for the long stretches between cities when you travel the interstates. Besides, how you gonna stay up with Fair, Balanced, and Unafraid without XM in the car?

But I love the talkers on AM radio, and most of em aren't on XM. Bruce Williams is on some AM, but IS on XM. the Art Bell/George Noory contengent is on AM in WDC, and NewYork City, but is also on XM. Laura Ingrahm, Shawn, Levine, and a host of other talkers I like are on various shades of AM radio, thankfully..

I mean, what am I gonna listen to, bankrupt Air America and Joe Picapoe and Al Frankin?

I love AM radio!

 

[Pablo]

It's definitely all the plugs. I checked all the components and grounds. I'm really thinking it's in the antenna. The antenna is in the left rear panel window (itsa wagon).

Now here's a weird one - I had just thrown my heavy jumper cables in the back, right below the antenna window the evening before the noise started. I took the cables out - the noise was attenuated (still there but much lower level). The loose cables were acting as a little receiver/repeater below the antenna. Strange. The noise was probably growing as parts aged......the saga will continue.

Mike - a couple things. Maybe a sharp young Asian guy like yourself will make it big, easy. A lawyer, a doctor. Somebody with big income. I'm not sure who pays for your XM or your parts shotgunning, but I have a family. I'm 48 years old and work my arshe off and G0D willing I'm going to retire with some money. But right now - paying for XM Radio would be a ridiculous luxury. I could give a chrap is you like AM radio - but we have some local talk that is excellent, and a few national guys are good too. Your idea to replace parts - well maybe not half bad - but again, it's on my dime.

 

[brianl703]

I'd suggest checking the ground at the antenna. It sounds like it may be bad, particularly if the problem started when threw the jumper cables in that general area.

A good test of this is to unplug the antenna cable from the radio and use a test light between 12V and the antenna connector shield (which is the outer metal part). It should glow brightly.

 

[The Critic]

Quote:

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Mike - a couple things. Maybe a sharp young Asian guy like yourself will make it big, easy. A lawyer, a doctor. Somebody with big income. I'm not sure who pays for your XM or your parts shotgunning, but I have a family. I'm 48 years old and work my arshe off and G0D willing I'm going to retire with some money. But right now - paying for XM Radio would be a ridiculous luxury. I could give a chrap is you like AM radio - but we have some local talk that is excellent, and a few national guys are good too. Your idea to replace parts - well maybe not half bad - but again, it's on my dime.

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First, I don't pay for XM. Neither do my parents. I get it for free on AOL Instant Messenger.

Second, I'm not suggesting that one recklessly shotgun repairs. In the event that an inexpensive part is in question (of serious nature), I usually replace it. My father agrees- he doesn't stress over small, inexpensive parts...we usually replace them if they're "known troublemakers," coming up for replacement, or are just inexpensive and would make the troubleshooting process easier. Perhaps my initial post was bit too far fetched...

 

[Rickey]

Pablo I forgot another possiability. The coil or coil wire could sound like buzzzz(all plugs). The coil wire(if it has one) is especially susceptable since it carries the combined spark energy for all of the plugs. A break in the resistive conductor may not immediately cause a miss as the voltage is able to jump across the break. The jumping current is like a spark gap transmitter in producing broadband low frequency RF emissions. If the noise is heard on other nearby AM radios it's probably the ignition system or engine grounding. If not then it's probably an antenna or radio grounding problem. Defective alternators may produce a whining noise that is propigated through the 12V electrical system. Good luck.
Rickey.

 

[brianl703]

You could test if the alternator is the problem by running the engine for a few moments with the alternator belt off.

 

[Papa Bear]

So Pabs, what's the verdict ?? What did you find ??

 

[Vilan]

A big rock, I'm guessing.

 

[Pablo]

Still looking....I had a new set of plugs in the garage, and while the old ones were well overdue (worn and huge gap) for replacement no improvement other than some new found low end power (amazing that).

Anyway - it's not the alternator, the grounds are all less the 0.3 ohms. The antenna is fine.

So that leaves the cap and wires. They aren't super cheap - but the wires are original (2nd cap and rotor).