Hey all, heard a strange noise the other evening while tooling up the Gold Camp Road up in the mountain. It was a strange rattling sound while under load going uphill, and seemed to be rpm independent, meaning I could just slightly ease off the pedal (not really dropping rpms much) and it would diminish; it didn't speed up or slow down in rate of sound, just fade out in volume. Wouldn't do it if I dropped a gear and romped it up the road. Any clues? Could it be something bad with the engine, or should I start trying to find something loose in the engine bay? FYI, noticed it mostly while cruising uphill in 3d gear at around 3k rpm, and by "rattling" just that--sounded like loose metal or rocks in a can....

Mine did something similar when the heat shield on the cat came loose.

Could be pre-detonation. (pinging)

Sounds like rocks in a can (kinda)

 

Do the same road with higher octane gas, and see

FNG, I did just get a new Y-pipe/cat installed recently, but I would assume being new the shield would be very secure???

 

As far as pre-det, I've been advised by others on the board that at my altitude (6000ft+ down in the city, obviously higher once up in the mountains) I should run with the lowest octane. I had asked once about running our, to me, crappy 85 in the sube....

mine does the same thing and its a loose heatshield.....its rather annoying isnt it?

All I can say is to check it. Things tend to loosen due to vibrations and extremes of hot and cold. Heat shields are susceptible to both of those and the bolts/clamps may have come loose.

run a higher grade of fuel and see if it goes away. maybe your ignition timing is set too advance. maybe run your shifts at higher rpms with less gas pedal, to reduce load. if haulng up a mountainside in 3rd gear, you will want to be in the 3000-3500 rpm range at least.

 

there could be carbon deposits in the cylinder causing hot spots. Try treating with sea foam to blow the carbon out of it. (ingest the product with a warm engine and let it sit for a half hour to soak in, then drive the hell out of it.)

Maybe "ingest the product" is poor wording?

Maybe "ingest the product" is poor wording?

 

LMAO /\ this

"run a higher grade of fuel and see if it goes away"

 

Could be heat shields tho, check to make sure. If it goes away with higher octane fuel it can be easily tuned to make it go away with the low octane stuff. Let us know huh?

 

Doug

I'll have to try some of that octane booster crap, as I JUST filled up the day before my jaunt up the trail and have barely used any gas since then.

Anyone have any idea what this sound is? https://www.dropbox.com/s/eq8ovnhwr1fr85b/rattling%20noise.3ga

Its certainly not rod knock no shavings in oil pan or filter plus its on and off as in one morning its there then gone for several weeks then back again.

I agree that low octane fuel will most likely be the problem assuming there is nothing loose. 'pinging' or 'pinking' as we say in the UK, often occurs under load in high gears when the throttle is open fairly wide and revs are low - the vacuum advance is advancing faster than revs can climb. If this happens when the throttle is only part-open then you need to either retard the static ignition (vacuum disconnected while setting) or use a higher octane fuel. If it only happens in high gear with the throttle wide open then just drop to a lower gear. Plenty of 'performance' cars of old were set with loads of advance and it was 'normal' to 'pink' occasionally. Prolonged pinking will burn a hole in a piston so you need to get to the bottom of the problem. If, when the engine is not too hot, you try the following test, you will know.  Find a level stretch of road and pull away gently and, using only part-throttle, short-shift so you are in 5th at about 40 mph; then, floor the throttle. If it pinks, you know it's an 'advance' problem caused by either ignition timing or octane number being too low. If it doesn't pink under those conditions then the sound is not pinking.

Edited February 10, 201313 yr by NickNakorn