Just tuned - now have radio noise

Reply

  #1  
Old 09-06-11, 08:45 PM
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 1,605
Just tuned - now have radio noise

Hi everyone,

My '97 Chevy G3500 extended with 5.7 had a miss due to small intake manifold gasket leak into #5. Had that fixed, later had a tune up. New wires, plugs and fuel filter is all. Runs good again. However I now have constant AM radio interference. Can someone tell me why?

With the old wires and plugs, (and also other vehicles), noise sometimes happened during very damp weather only, would go away after warm up. Mechanic says lets try a new distributor cap. I'm OK with that, but it didn't make noise before. Opinions......

Jaz
 
Sponsored Links
  #2  
Old 09-06-11, 11:37 PM
Member
Join Date: Mar 2009
Location: Texas
Posts: 1,051
One possibility is in regards to the quality of plug wires that were installed. OEM wires have noise suppression capability, but if cheap ones were installed all bets are off.
 
  #3  
Old 09-07-11, 07:29 AM
chandler's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Dec 2005
Location: USA
Posts: 39,968
Jaz, equinox may have it hit dead on. I do remember in the 60's the old ignition systems we had to put a condenser on the low voltage side of the coil to ground. It took out the AM interference. But, hey, AM is all we had!
I think a gooder quality of wires would help.
 
  #4  
Old 09-07-11, 10:26 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,094
A walk back in time .
If it is bad wires, all of them, then the ticking noise would be faster than just one bad wire. I have experienced one wire not pushed all the way onto the plug and causing the interference. Judging fast and slow depends on how fast the engine idles. Our old v-8's would slow way down and one bad wire would approach where you could almost count them. Maybe some of the old mechanics can describe it better.

Distributor cap? if it was ok before it should be ok now, as you were thinking.

Bud
 
  #5  
Old 09-07-11, 03:37 PM
Member
Join Date: Mar 2009
Location: Texas
Posts: 1,051
I can remember two kinds of AM radio interference sounds, but then again I can hardly remember what AM radio is now also. First was a whinning sound that increased with engine speed. That often would come from interference from the alternator. The other would be a spuuut spuuut spuuut sound, also varying by engine speed, and that often would mean at least one plug wire leaking spark. It might be also a good idea to make sure all the wires are properly secured in their routing clips, and none are riding on hot surfaces.
 
  #6  
Old 09-07-11, 07:31 PM
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 1,605
Thanks guys.

I asked for Delco wire set and I have no reason to believe they gave me something else. Kinda hard to see them as you know. I was charged $125.85 for the wires.

In the past with other vehicles needing a tune up, the noise increased with engine rpm. Not the case here. It's a constant crackling noise when the engine in running.

I doubt it's the cap too.

Jaz
 
  #7  
Old 09-08-11, 07:10 AM
Member
Join Date: Oct 2008
Location: New England
Posts: 10,094
If it doesn't vary with engine speed then I doubt it is related to your ignition wires. More like the antenna got disconnected. Just guessing.

Bud
 
  #8  
Old 09-08-11, 09:04 AM
Member
Join Date: Mar 2009
Location: Texas
Posts: 1,051
Something with the antenna or shielded coax supply cable and or the cable connections would be another guess also at this point for sure. It still sounds like electrical interference either way. Is there any interference with only the key turned in the on position (not ACC) and the engine not running. If so it could be coming from the fuel pump for example. There is also a possibility of a poor or corroded ground somewhere if the radio antenna and cable check out OK, and it is shown not to be ignition related. Are there any other known electrical issues with the truck with things like lamps,bulbs etc?
 
  #9  
Old 09-08-11, 07:52 PM
Member
Thread Starter
Join Date: May 2007
Location: USA
Posts: 1,605
I don't see how it can be an antenna problem since the radio works fine except of when the engine is running. Plus FM is fine all the time. The only things that has changed are the wires, plugs and fuel filter. There is a gremlin with one dim stop lamp when the running lights are on. But that has doing that for several years.

Jaz
 
  #10  
Old 09-08-11, 08:46 PM
Member
Join Date: Mar 2009
Location: Texas
Posts: 1,051
FM and Am are two distinct scenarios and you can easily have no problem with FM but issues like you have with AM reception. While you say all is probably ok with your antenna, if for example it is a little loose and not grounding well, and for whatever reason there is a poor ground or missing ground at the radio you can have noise problems. I also mentioned in a past post to check all of your grounds and clean and tighten as required. This includes battery cables , and engine ground straps. Not sure if you have done that or not. You can also buy noise limiters that are cheap and go into the power line for the radio. These especially work well when AM radio noise is generating from the alternator. Also if the noise really is ignition related is there a possibility that all new spark plugs are generating noise. Were different ones installed this time around that do not have adequate noise suppression characteristics. This requirement is changing as people opt out of AM radio altogether and listen to digital memory device players, FM and now satellite. You are on the right track when you talk about what has changed with the tuneup. I would confirm exactly what plugs were installed and also confirm not just the brand of high tension wire that was installed but what expected performance they provide. The days of the so called Delco brand meaning original equipment are long gone with the GM products.
 
Reply

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Thread Tools
Search this Thread
Display Modes