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Old 09-17-2004, 05:29 AM   #1
dcwrx2
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Default "Electric zapping/buzzing"-like Noise at WOT, 1st&2nd Gear @ 5000+ RPM, A/T '04 WRX

NOTE: Figured out the problem IS detonation. It's gone after a custom tune.

After my '04 A/T WRX break-in period, I tried flooring the accelerator in order to feel the acceleration. Yes, the acceleration is great compare to my previous car. However, here is a problem I faced:

When I floored to bottom (WOT) at either 1st & 2nd gear and see the tachometer rev up, I will hear noise at about 6k-7kRPM, or sometimes at ~5500RPM as well (in case if at 1st gear). Or in other words, this noise happen at about 1 second before tachometer hit 7kRPM and upshift. I believe the noise is from under the hood, and it sounds like "electrical zapping" or "electrical buzzing," come in very short pulses. Here is a good example to illustrate: Think about those electrical insects killing trap with a backlight fluorescent lamp, and there will be "zapping/buzzing" sound when the insect flies towards the lamp and hit the conducting wires. That sound from under the hood is very similar to this, except it has lower pitch.

So far I tested and it seems the noise will not happen in 3rd or 4th gear.

Another thing, as long as I'm not at WOT (That is, there is at least an inch or 2 apart between the accelerator and the floor), there is no such noise at any RPM range and any gear.

My '04 4eAT WRX is 100% stock, no ecu reflash, no mods, etc. Can someone advise me what can this noise be? My guessings are: 1) Noise from stock bov/wastegate/some fancy safety feature? 2) Knocking noise?
Guessing #1 is because this noise only happen at WOT AND first 2 gears AND close to redline.
I doubt it is engine knocking (but can't be 100% sure) because I experienced such noise from my previous car, where the sound was like "a bolt/nut spinning inside an operating washing machine," and I'm sure this "zapping/buzzing" noise doesn't sound like that.

Any ideas? Pls advise =)
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Last edited by dcwrx2; 10-28-2005 at 05:43 PM.
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Old 09-17-2004, 07:12 AM   #2
Celly
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Take it to the dealer.

Or, Leave it as it, and on hot summer nights use it to keep mosquitos off your porch...
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Old 09-17-2004, 07:26 AM   #3
dcwrx2
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I hope to get more feedback from other 4eAT owners, specifically 2004 model, bone stock, and did WOT their WRX, before I send it to the dealer...
Moreover, it doesn't throw out CEL, nor I feel power surge at the moment I hear those noise.
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Old 09-17-2004, 09:11 PM   #4
dcwrx2
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Well, I think I will just go back to my rex dealer and show them the noise, and see what the answers come up. I have a broken driver seat height adjustment lever under normal use, so I need to go to them anyway to claim the warrenty...

Before I'm going to make an appointment, can some 4eAT WRX owners reply to this post please? Whether or not you have the same problem, I need some feedback please.
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Old 09-17-2004, 09:31 PM   #5
Russ77
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take it to the dealer just to be careful. the best bet would be to become friends with somebody who has DeltaDash or any other data logging software and find out for yourself what's going on. I have an AT wrx and they make some wierd noises at full throttle.
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Old 09-17-2004, 10:17 PM   #6
WRX_02_227
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Maybe one of the coil packs is arching onto the engine somewhere.

Do you have to be rolling to have this happen or will it happen in neutral or park?
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Old 09-18-2004, 06:34 AM   #7
dcwrx2
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So far I can repeat the noise when my car is running in 1st and 2nd gear (mainly when engine rev up in the 6k-7kRPM range), but not in 3rd gear, or park, neutral.
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Old 09-18-2004, 12:16 PM   #8
impreziveWRX521
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could it possibly be the rev limiter kicking in?
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Old 09-18-2004, 03:27 PM   #9
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Quote:
Originally Posted by impreziveWRX521
could it possibly be the rev limiter kicking in?

I take it you have never bounced off of your rev limiter....
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Old 09-18-2004, 06:05 PM   #10
impreziveWRX521
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no, never
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Old 09-18-2004, 06:10 PM   #11
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wild guess but... vibration?
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Old 09-19-2004, 06:20 AM   #12
dcwrx2
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Yeah I'm also guessing some vibration, but shouldn't be rev limiting problem, coz this problem happens before redline (7kRPM), and like I said, if I release the pedal a bit (an inch or 2 above the floor carpet), then no noise at those RPMs...
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Old 09-19-2004, 02:11 PM   #13
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I had what sounds like the same problem. (even though I drive a 5MT) It happened when I installed a grounding wire from my (-) battery terminal to the drivers side engine bay wall. I removed it, and unplugged my battery so that the ECU would reset. After that, it went away..... Never knew what it was... Try unplugging your battery (leave it unplugged a good 30sec to 1 minute) and then go for a drive. Let us know if this fixes the problem!
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Old 09-20-2004, 02:37 AM   #14
dcwrx2
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Ok, I'll try this method and see how it works. Thanks for the suggestion.
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Old 09-21-2004, 07:56 PM   #15
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Today I reset my ECU (fully warmed up -> disconnect battery -> step on brake for half minute -> wait extra 5 minutes -> reconnect the battery), and tested the car...

Well, now I guess those noise is knocking indeed, because of the following results:

After I reconnect the battery and started up the car, I performed "Vishnu" method (left foot brake to build up a bit boost at low RPM for 5 seconds), then ran on locals for few blocks, and then try to pull on freeway. WOT while doing uphill on ramp, and the noise is coming out again, in as soon as 5k-6kRPM range. The noise also exist in 6k-7kRPM range. Frequency of occurance -- quite a lot.
I off ramp at next exit, made a left turn, and on ramp again. WOT again, and now the noise occurance frequency happened to be fewer, but still in about the same RPM range, 5k-7k. I off ramp exit at the same one I uphill on ramp from, made a left turn, on ramp again (to maintain consistance of testing). WOT again, and surprisingly the noise occurance frequency happened to be significantly fewer compare to the "1st WOT" (same uphill on ramp) and also fewer compare to the "2nd WOT". Noise happens in 6k-7kRPM range but no more in 5k-6kRPM range too! I repeat on/off ramp for like 10 times and turns out now the noise happens rarely in 6k-7kRPM range. (I also notice my gasoline level DID dropped a bit... $$ flew away easily). On the other hand, I tried WOT with both A/C on or off, no feelable boost lost or power surge or anything.

Conclusion, after the WOT test results + what I read from user manual, I believe those noise are indeed PINGS, but I guess my car should be very ok from that because like the user manual mentions, "some pings at heavy acceleration is expected and it doesn't indicate a problem of the car" (I know pinging IS a problem, haha). However, one thing I experienced is that the ECU does learn about the quality of fuel and adjust the timing from pings. It is shown by comparing the frequent pings at 1st WOT right after ECU reset, and the thereafter WOTs which give significantly less pings.
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Old 09-21-2004, 08:40 PM   #16
Predator3
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Quote:
Originally Posted by dcwrx2
Conclusion, after the WOT test results + what I read from user manual, I believe those noise are indeed PINGS, but I guess my car should be very ok from that because like the user manual mentions, "some pings at heavy acceleration is expected and it doesn't indicate a problem of the car" (I know pinging IS a problem, haha). However, one thing I experienced is that the ECU does learn about the quality of fuel and adjust the timing from pings. It is shown by comparing the frequent pings at 1st WOT right after ECU reset, and the thereafter WOTs which give significantly less pings.
Somebody please hand this man a Nobel prize for discovering the secret behind our Subi's ECU!

However, if your car is still making the sound i would still take it to the dealership...if ur stock.
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Old 09-21-2004, 10:28 PM   #17
zoomfactor
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If you have that much "pinging", what fuel are you running? Premium right?
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Old 09-21-2004, 11:03 PM   #18
MFactor
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I would take it to the dealership inspite of what the manual says. Even if the dealership says its normal at least you can have it documented and if something does indeed happen you'll have proof that you've attempted to get the problem resolved before it caused any serious damage.
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Old 09-21-2004, 11:18 PM   #19
dcwrx2
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Yeah, I just made an appointment with the dealer, coz I have a broken seat height adjustment lever need to be replaced under warrenty. Over the phone, I said I hear pinging noise under hard acceleration and she said she will make sure the tech will take a test drive with WOT acceleration.

I'm running with branded Californian 91 fuel.
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Old 09-28-2004, 08:46 PM   #20
dcwrx2
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I went to the dealer, had very BAD experience (CLICK HERE if you want to read the story), but I think the problem is somehow gone now coz I couldn't duplicate the noise today (I indeed tried WOT at 1st and 2nd gear, unlike those techs at dealer who didn't even test drive my car). I assume it's the ECU which finally recognized what timing to use (I'm using 91 octane tho) and eliminated the ping noise. Anyway, I pray for my car to be longlasting.... still a long way to paying it off, lol.
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Old 09-29-2004, 03:37 AM   #21
drees
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The moral of the story is: Don't do the "Vishnu Reset" if you suspect that your car is on the edge of detonation, you will make the engine detonate for sure that way! The the engine learn normally, and the chances of encountering severe detonation will be much lower.
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Old 09-30-2004, 02:13 AM   #22
dcwrx2
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Someone has similar problem said, the noise was actually from a heatshield of somewhere. Once it is fixed, no more noise.
For me, I didn't do anything on any heat shields, but the car doesn't make that noise now, so far so good. I'll try to forget about it but keep my ears on the noise when it comes up again.
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