New sound started coming from the motor tonight, has me worried...

georgio440 · Mar 16, 2008

Tonight I noticed a kind of rattling noise coming from the engine when it hits about 2,000RPMs. This happens not only when accelerating, but also when revving it in neutral. It almost sounds like a pebble being spun around in a plastic cup, to give you an idea of what the sound is. Like I said, it starts at about 2,000RPMs and gets louder as the revvs increase. Any help is greatly appreciated. Thanks, guys.

georgio440 · Mar 16, 2008

Anyone? I'm taking it to the shop this week to have it checked out, but I just wanna know if this is a common or severe problem.

ky_kneedragger · Mar 16, 2008

georgio440 said:
Anyone? I'm taking it to the shop this week to have it checked out, but I just wanna know if this is a common or severe problem.

how many miles are on it? my car made what sounds like the same noises and i later found that my timing chain had worn through the guides and into the tensioners!!! it costed me 131.00 at a Ford dealership with my discount.my car has around 65,000 on it..

the98stang · Mar 16, 2008

We can't really tell you with out seeing it in person. I would do a compression check to see if the engine is holding up.

georgio440 · Mar 16, 2008

It's got about 70k on the ticker. I just thought this might have been something common, which would mean my description would give you a good idea as to what's going on.

georgio440 · Mar 16, 2008

I'm also just worried about a bad rod bearing or something of that nature.

nyuk98gt · Mar 16, 2008

georgio440:

A rod bearing is a low, deep knock that can be heard at idle and increases with engine speed.

First thing to check is that all plugs are snug. It is possible that one has backed out a little and you want to get it before it rips the threads out of the head! Check ONLY when the engine/heads are cold (overnight), please.

Are you hearing detonation (pinging, pre-ignition)? Sounds like marbles in a tin can. As the engine ages and carbon builds up on the head, the volume of the combustion chamber decreases (carbon takes up space) and the timing becomes a little too much. Try a tank of 93 octane and see if that helps.

Another culprit might be your cam chain tensioner(s). I think this is unlikely because you would hear it mainly at idle when the oil pressure is not at peak. As engine speed goes up, the pressure stabilizes and will keep the tensioners pumped up. Of course, if there is an internal problem with the tensioner, then oil pressure won't make much difference.

Have you made any changes to the tune to cause the noise? (No flame intended, just trying to rule out possibilities).

Chris

georgio440 · Mar 16, 2008

Nyuk, no changes have been made to the tune. As for spark plugs, I'll go check if any are loose right now. I'm not sure about it being detonation, though. It just started last night, and I've always filled it up with 91 (I've never seen 93 out here in CA).

georgio440 · Mar 16, 2008

Well, I made sure all the plugs were secure and took her for a ride. The sound is gone.

nyuk98gt · Mar 16, 2008

georgio440:

Good! Glad to hear all is better. I didn't think about 93 vs. 91 octane, lol. Thanks for the update.

Chris

georgio440 · Mar 17, 2008

Hmm, weird thing happened. After a bit of driving, the noise came back. It only occurs under mild acceleration at about 2-3k RPMs. If I go a little harder, the noise disappears. Is it possibly detonation? I always fill up with 91 at Shell, but my last fill up was 91 at a janky 76. Could the different gasoline be causing this, despite having the same octane rating?

nyuk98gt · Mar 17, 2008

georgio440:

Gasoline quality could be a factor. How about cleaning the MAF (if you have an oiled air filter)? The oil can foul the wires and cause a lean condition. Just be very careful when cleaning it because the wires are very small diameter and brittle. There's a spray cleaner that is called "MAF cleaner" (duh!) so you don't have to touch the wires. You can use electrical contact cleaner, too, because it does not leave a residue.

HTH,

Chris

RedDaemon · Mar 17, 2008

are you SURE its coming from the engine?

check your catalytic converters. im assuming you have them sicne you live in california

H What 4.6 · Mar 17, 2008

-=NightHawk=- said:
are you SURE its coming from the engine?

check your catalytic converters. im assuming you have them sicne you live in california

Thats what i was thinking as i was reading..... it could be/ most likely is something simple.... perhaps a rattling heat shield??

screamin gt · Mar 17, 2008

the98stang said:
We can't really tell you with out seeing it in person. I would do a compression check to see if the engine is holding up.

easy and can tell you alot. if the problem is in your engine.

jstreet0204 · Mar 17, 2008

-=NightHawk=- said:
are you SURE its coming from the engine?

check your catalytic converters. im assuming you have them sicne you live in california

+1
A chunck of the cat material can break off and make this noise.

BLOWN00GT · Mar 17, 2008

i spun a rod bearing in my 00 GT. she had around 80,000 on the odometer. it would make a knocking sound at the same exact RPM range as yours. and sometimes it would not do it. which could have fooled you to believe the spark plugs caused it. when at idle i would not hear the noise. but if sitting and revving the motor it would make the noise around 2500 and eventually go away around 3500.

i ran my car hard all the time, drag strip and road. also would downshift hard to slow down faster. which is not good for the car!

it got alot worse over a few months and i finally tore it down!

hope yours isnt the same thing. good luck with it!

georgio440 · Mar 17, 2008

It's definitely not the cats, as I have an O/R X.

But what BLOWN00GT described sounds exactly like what I'm experiencing, so now I'm all paranoid about needing a rebuild.

snidehockey · Mar 17, 2008

currently running on bad rod bearing(s). ran the car almost dry of oil (even though dipstick read full). I checked the dipstick it said full - but when I drained the oil about a quart came out. So it was being run on like no oil and the bearings have since done exactly what you're talking about.

The way I hear it the most...in 3rd gear get up to like 40 mph and hold it there....then gradually accelerate still in third. Those things start clackin away.

I've had this condition since before Thanksgiving.

Just biding my time til I can replace the motor.

georgio440 · Mar 17, 2008

Well I changed my oil less than 3k miles ago... So yeah.

But yeah, if it is a rod bearing, does that mean I need a new motor?

New sound started coming from the motor tonight, has me worried...

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