im putting this here since you audio guys have to deal with this alot..


this started yesterday.... im getting electrical noise in my wiring system... its not only causing a slight noise in the speakers, but when i rev the motor, it makes enough noise to fool my SGI box into making my speedo jump around.

its not the usual alternator whine that changes with RPM either.. its a kind of crackle.


i did the usual suspects, checked connectons, grounds, positive wires, battery connections, re-checked the grounds, on the SGI box i moved the power, ground, signal out, and signal in all away from each other....

i donno whats causing it. its def electrical noise, and its mostly when i blip-rev the throttle....



the alternator is about a month and a half old, best NAPA has.. battery is also brand new.. im getting full output from both the alt and the batt..

the only mod done to the car before this started was a swap from automatic trans to manual.... but i highly doubt my manual trans is somehow making electrical noise in the system... but i'll put that out there anyway..


ideas?

 

Only thing I can think of is check to see if any wires were pinched during the installation of the tranny.

You have checked everything else.

Good luck.

 

When you say 'crackle' and the fact that it happens when you blip the throttle, I think ignition noise. Maybe you've got a plug wire going bad, or working loose. Maybe the distributor cap isn't fastened down squarely and it has opened up the gap between the rotor and the posts on the cap.

That's where I'd be looking right now.

 

get some better spark plug wires w/ better insulation maybe?

 

THATS A VERY GOOD IDEA!

i did pull the cap off when i did the trans swap.... perhaps it worked loose or somthing... or a wire isnt on..... i'll check that tonight!


thanks!

 

Another thing to look at in the cap is the rotor bushing. It also may need replacing. They come prepackaged with new caps and new coils.

 

new cap, rotor, and wires.....


same problem.


i think the ignition noise idea is on the right track though....
what else would be a source of ignition noise.... i havent modified the primary side, so i think its in there.... other then the plugs themselves, the 2ndary side is new..

 

The tach lead could be bringing electrical noise into the cabin of the car because it is carrying the pulses of the primary side of the ignition, but it sounds like you have rerouted this stuff so the wires are reasonably separated.

How does the speedo get it's signal, is there a sensor connected to the transmission? Perhaps that is picking up something.

I'm not familiar with the VSS system/electric speedos etc - just the mechanical speedo system.

I can't think of anything else yet...

 

tach line is way under the dash.. untouched from stock. i dont even know what color wire it is. (if someone knows, what color and where it is, post up)


the stock VSS sensor wires used come out near the tailshaft.. they now come in (away from all other wires) thru the auto shifter cable hole.

there, one goes to ground, the other goes to sensor out on the SGI box.

SGI gets power from fuesbox... ive routed that wire FAR away from all wires) (closest wire is 3" away)

the T56 VSS sensor gets grounded, and goes to signal in on the SGI box. its two wires are twisted around each other.... also its away from all other wires.

the 2 sensors and SGI box are all grounded together at the same point to eliminate ground faults.



im getting some noise SOMEWHERE though

im thinking underdash now

 

How are the grounds in the engine compartment? Specifically, the one at the rear passenger side head? (there should be a ground strap in that area)

How loud is the crackle noise?

None of the spark plugs loosened up, did they?

 

grounds check great, including engine grounds, both stock and my added ground strap.



the crackle is very mild sounding in the speakers.... you have to have the stereo on, but turned all the way down to hear it...




i havent checked how tight they are, but i doubt the came loose. im changing them this weekend anyway.

 

got it. i have no idea why.... theorys welcome.

the power wire to the coil from the factory comes back from one side of the distrib.


i had it going around the distrib the other direction.... as far as i can see, im not close to any other wires really...

i unplugged it, routed it the stock way, (so it comes out of the harness on the the other side of the distrib) and plugged it back in...

noise and speedo flicker are gone.

WTF!?

 

bad connection at that very connector. happens all the time, sometimes just unplugging and re-connecting the plug will fix it.