Crazy electrical "zapping" noise when boosting in 5th

[PieEyedPiper]

This was the second time it's happened within a week.

Short Version

Crazy electrical "zapping" noise when boosting in 5th. Went away immediately when I let off the pedal. Really creeped me out, what was it?

Long Version

Today I was on the highway at 3k rpm just cruising. Had not been beating the car or anything, in fact, had just given it a detailing yesterday and did some fluid maintenance a few weeks ago. I go to give it some gas, not a WOT pull or anything just enough to reach full spool on the T-25 and start movin'. But as soon as I started to spool, I got the loud typical T-25 sounds but at the same time I was spooling I heard a really loud electrical buzzing or zapping kind of sound coming from what I thought to be right behind me. My passenger, though, thought the sound came from her window. We were on the highway and we all know about 2g road noise; so it was hard to identify the source.

I probably only hit 11lbs, instead of the full 16lbs I normally reach, before I reacted to the noise and immediately let off the pedal. Since I reacted so quickly I did not get a chance to perceive if the engine was operating any differently because of this anomaly.

The only things behind the driver are the fuel pump, washer fluid stuff and my amp.
I never hit any of the buttons related to the washer stuff.
My amp was off, no power to the unit at all.
My fuel pump is stock, 107k miles, rewired with a Radio Shack relay.

My immediate conclusion was that it was my fuel pump freaking out or perhaps my Radio Shack relay was the part tweaking out back there? I'm sure it is not of the highest quality when it comes to electronics.

My passenger still thinks it came from her window

Soooo, anyone wanna take a stab?

 

[turboglenn]

Man, that's an odd one.. I'll do some thinking and looking over on my car to see if i can get an idea of what it might be. But let me aska few things first.

1.) is it ONLY in 5th that this happens?

2.) how much boost before ou start to hear it?

3.) do you have a way to make sure your AFR's are safe while this is happening? If so, let it "zap/buzz" whatever adn try and find it while it's making teh noise if the motor is safe while it's happening.

 

[PieEyedPiper]

Man, that's an odd one.. I'll do some thinking and looking over on my car to see if i can get an idea of what it might be. But let me aska few things first.

1.) is it ONLY in 5th that this happens?

2.) how much boost before ou start to hear it?

3.) do you have a way to make sure your AFR's are safe while this is happening? If so, let it "zap/buzz" whatever adn try and find it while it's making teh noise if the motor is safe while it's happening.

Thanks for putting some thought into this for me, really appreciate it.

1.) only happend once or twice, the first time could have been phantom knock though. I have only noticed this on the highway when giving it some gas in 5th. (5th is probably irrelevant info, just calling it as it was though).

2.) I heard it after about 2lbs.

3.) I'll put the logger back in the car and see if anything weird is going on with timing / o2's etc and see if I can catch it doing the noise. But I bet it will be tough to time it so well. I can't predict when it will do this or if it will happen again.

Thanks!

 

[Icarus]

Just a long shot, but check your plug cables. If one of them is shorting out, it can create a a zapping sound (RFI) coming from the radio. In the past I've noticed it being louder when under load. They can be hard to detect. Here's a guide to help out:

magnecor guide

 

[luv2rallye]

I agree - or plug cables that are "open" or not making contact. Spark will then usually jump around outside of coil or whereever it can to get to ground. Check coil case for burns. Can also rev up engine in dark while watching under hood for spark from coil or plug cables.

 

[assault187]

Although I knew this was coming from the engine bay, one of my alternators at WOT work shoot sparks all over the place while making a zapping whirring sound.

 

[PieEyedPiper]

Just a long shot, but check your plug cables. If one of them is shorting out, it can create a a zapping sound (RFI) coming from the radio. In the past I've noticed it being louder when under load. They can be hard to detect. Here's a guide to help out:

magnecor guide

I agree - or plug cables that are "open" or not making contact. Spark will then usually jump around outside of coil or whereever it can to get to ground. Check coil case for burns. Can also rev up engine in dark while watching under hood for spark from coil or plug cables.

Would having my headunit turned on or of have any effect? My headunit was off and my amp off, thus the speakers were with no power. Is it still possible that RFI or whatever else from spark plug wires could cause that kind of feedback/sound to eminate from my speakers?

I will check when it stops raining to see if I'm getting a "light show" or if there are any visible burn marks.

Although I knew this was coming from the engine bay, one of my alternators at WOT work shoot sparks all over the place while making a zapping whirring sound.

I've been keeping a close eye on my alternator lately, I'll look in that area too for any monkey business.

In the meantime, anyone have any input on my fuel pump/rewire relay idea?
Thanks