Detonation...again...and again

DocG · Oct 5, 2005

Hey all. Still trying to figure out my strange noise on my 04gt. Let me break it down, then maybe somone can offer a good next step for me!?!?

1) KN Air filter, removed silencer - knocking seems worse after this install, but I only had the car for 2 days prior.
2) Cleaned MAF sensor - about a week after KN went in, no improvement
3) Tried 93 octane, now 89 octane, no improvements

Car makes "pinging" type noise, metallic rattle. Does it throughout RPM range, speed range, weather range, warmed-up, running cold, etc. Today I am almost positive I heard it after letting off the gas, the noise continued for 1-2 seconds while coasting.

Also "pings" when sitting in neutral ( I believe with clutch in and out), but strangely when I popped the hood to listen for it, I couldn't hear the noise either in the car or under hood....but close hood, and all of a sudden you can hear it, especially when first pressing on the gas pedal. Almost sounds like it coming from under the car when your in car with driver door open.

Starting to think it might not be detonation since it doesn't seem to be affected by load and the octane changes didn't phase it. Almost seems like it is getting worse the more I drive it. Would a bad "cat" sound like this, maybe exhaust leak? I still want to pull the plugs, would detonation definetly show on the plugs? I don't want to keep beating a dead horse here, but hate to keep looking for the wrong problem.

Maybe I should just convince my wife the cat's are bad and I need new X-pipe along with cat-back system just to be sure?!?!?

DocG · Oct 5, 2005

Oh, and I've been debating a dyno run with A/F wide-band readings? I know this would tell me if I'm lean/rich....but would it be a good way to tell if I have detonation?

Thanks!

Torinalth · Oct 5, 2005

possibly, detonation can happen in many instances, but because it can be caused by a lot of things its hard to pin down, just like me. i think i am running lean so i am going to get a tuner to richen the mixture. aside from not enough fuel it can be from heat, low octane, and too high compression (can be fixed with higher octane), and finally timing too far in advance.

i can understand the issue with finding the sound when the hood is up... reason is that there is a lot of ambient sound that can drown it when the hood is up... i dont understand it either, but it happens.

if you know the car is completely stock aside from the K&N then put the stock filter back on, and take it back to the dealer (seeing its an 04, it should still be under warranty). if its not under warranty, then it might be benaficial to dyno it to check to see if you are running too lean.

on a side note, if you have the ability and the time, you might want to check your spark plugs to make sure one is not backing out on you... can cause a similer noise from what i have read. one more thing it COULD be is that if its all the time, there has been a problem with some peoples heads that the valves tick rather incessantly. so if you can put it 100% stock with litttle issue and have a warranty i'd get the dealer to fix it for free before i look into other areas.

Torinalth

ADRENLN · Oct 5, 2005

i dont know what it is either, but i been trying to hunt down the same type of sound you are talking about. i made alot of posts about tapping noise. i still dont know what it is.

your description sounds just like what my car is doing. car really sounds like crap ticking past everything while driving. and it sounds worse when you first give it gass then the exhaust kicks in and hides it a little.

i can only imagine detination or exhaust leak. i have had a dyno tune and i still get it. also after my mods it seems to get louder.

03ghoststang · Oct 5, 2005

a busted cat will rattle under most circumstances so you should have that looked at it might be the cat from what you described

Will Smith · Oct 5, 2005

Like the others have said it could be a exhaust leak right at the block, I doubt it would be detonation due to the timing but you might want to check that as well. and It could be as bad as the main bearings going out.

DocG · Oct 5, 2005

Hopefully with only 22k miles, its not main bearings. Would be suprised if its the "cats" even at those miles, but I'm running out of options. Thanks!

hotmustang331 · Oct 5, 2005

I have the same problem sometimes, I think mine was the MAF wires rubbing/hitting the firewall....I moved them (bent) and it seemed to help. I really dont hear it anymore.

KronicRacer · Oct 5, 2005

might be the fuel.....

i recently changed to texaco after using hess and shell for the longest time. with texaco fuel so far theres no more shuddering or popping and its getting a better burn than that other stuff.

what fuel are you guys using

it might be the culprit

ooraceredgt · Oct 5, 2005

an exhaust leak usually doesnt rattle it is more like a loud sput and it will get really loud. i had a similar problem with mine and what had happened is one of my mufflers got pinned against the under carriage and everytime the car would move and even soemtimes under idle i would get this hoorid rattle sound coming from the car. took a while to figure it out. you also could have a flange bolt just spinning freely. hope this helps

DocG · Oct 5, 2005

I've been putting Shell gas in it. Messed with it a little more just now. All the back-end of the exhaust seems snug, but it may be a leak up towards the stock manifolds (or do they actually call them headers?).

Strangely, I've noticed the car sounds a little bit different lately, doesn't seem as throaty and loud at low rpms, 1k - 2.5k....once I really get on it, it gets louder, but even with stock exhaust the thing seemed pretty loud at low RPM's a couple of weeks ago. Is it possible an exhaust leak or bad cats would do this? Almost sounds "air'ier" if that's a word. At low RPM's I hear more air flowing (more like a whoosh) than rumble. Guess its time to take the service guy for a nice test drive.

Is it normal to see a lot of condesation and water coming from the tailpipes and up near the cats after letting it idle and throttling it in neutral?

MAXX RS4 · Oct 5, 2005

I have the same exact problem. I think I may have just recently figured it out on complete accident. While using seafoam, I was videotaping the smoke show and after watching the vid I noticed that smoke was coming out of under the car. (http://media.putfile.com/CIMG1145). I ran some more seafoam through my car today and sure enough there's a leak right before one of my mufflers which I now strongly think might be causing the sound I'm hearing.

If you wanna check for an exhaust leak do what I did and have a buddy rev it up for you to find out if anything is smoking under there.

MaxedGT · Oct 5, 2005

If it does it at idle, its not pinging. If it's under warranty why not take it to your dealer?

SLY GT · Oct 5, 2005

"Some vehicles, equipped with the 4.6L 2V engine, may exhibit an engine tick noise that is present at all temperatures during idle. The noise may be emanating from the valve guide area in the Cylinder Head. The noise may not be heard with the hood open." This was from an earlier TSB. Also, check for a loose spark plug.

Kilgore Trout · Oct 5, 2005

All of the above are excellent suggestions. I would also suggest checking your sparkplugs to make sure they are tight. You should do this when the engine is cool and as soon as possible. Spark plug blowout would occur after the ticking goes on for a while.

I think it is either a spark plug getting ready to blow out or it is an exhaust leak.

ADRENLN · Oct 5, 2005

water coming from the pipes at idle is normal. i have the same air sound at low rpms. that is where i hear the ticking he most also. i can hear the ticking as i get on it harder, but it is more masked.

me and you seem to have the same problem.

i dont think its the tsb, caused i changed the heads and now i have the ticking and air sound louder. the air sound almost sounds like the car is really struggling to get the rmps up. the car dont seem to lose power but sounds really weak.

is this kind of what you get Doc?

ADRENLN · Oct 5, 2005

my cams kind of throu it off i think, cause i think they tick a little too.

do cams kind of make a ticking sound as the move?

DocG · Oct 6, 2005

The more I seek answers, the more questions I have...haha. But...it is still under warranty, but when I took it in for an inspection and mentioned the noise, they say they didn't hear anything out of the ordinary. But I'll take it back to them again, and stay there with it until I can show them the noise I'm hearing.

I'm going to check the plugs if I get a chance before taking to dealer, but never have a chance while the engine is cool.

When pulling the coilpack things off the plugs, does anyone have problems with them clearing the fuel rail which seems right above them. I know there's the small bolt holding the pack on, but almost a couple centimeters above that is the chrome rail attached to the fuel injectors, seems like it'd be in the way.

Once I figure this out, I'll share with everyone who might be having the same prob. Thanks!

DocG · Oct 6, 2005

Adrenalin.....my car seems a little weaker, and the exhaust sounds a little less loud...but I'm not sure if its just my imagination and the thrill of the sound and speed is wearing off and I'm getting used to it. Or it could be the 93 octane gas I was running....I think someone on here said once that their car felt like it was towing a trailer on higher octane gas since it was not tuned for it.

Kilgore Trout · Oct 6, 2005

DocG2828 said:
When pulling the coilpack things off the plugs, does anyone have problems with them clearing the fuel rail which seems right above them. I know there's the small bolt holding the pack on, but almost a couple centimeters above that is the chrome rail attached to the fuel injectors, seems like it'd be in the way.

There is no need to remove the fuel rails. The COP will come a bit sideways out from under it.

Do yourself a favor and clean and condition the COP rubber boots with silicone spray while you have them off, they will seal better to prevent water in the wells and will come off a lot easier the next time

Also, put a dab of silicone dielectric compound on the spring where it connects to the top of the plug.

DO NOT OVER-TORQUE THE PLUGS! Torque to spec only with an actual torque wrench.

If you remove a plug to inspect it, be sure to blow the debris out of the plug well prior to plug removal. Check any removed plugs for torque after a few weeks.

Detonation...again...and again

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