engine rattle

[b2089]

This is hard to explain because I don't know how to describe the rattle. I've been told that it's the sound that lifters make when they aren't lifting properly. It's a faint sound, imagine a clock ticking with the sound of a vacuum leak metamorpshed together.

Now that I'm past the description, my car makes said knock very faintly when either going up a steep hill with the cruise on or accelorating moderately fast, but not gunned (I don't gun it, but faster than moderate and I don't hear it.)

It doesn't do it often and it's so faint that with the fan on 2 I can't hear it.

Any clues what to think? Maybe it's normal and I've just never noticed it before. I had a Grand Am with the Iron Duke engine that sounded like that but much louder and almost constantly for 100k miles, but this car is newish so I want to catch possible issues.

[pokesmot]

any knocking is never usually a good sign; however the fact that it happens "rarely" and is very quiet is a good sign. If the knock becomes more evident in terms of loudness and / or frequency you should get it checked out ASAP!

how many miles do you have on this engine, have you had any major work done to it?

have you done a tune up within the past ~40 - 50,000 miles?

the knock might not even be coming form the engine, but rather somewhere else (endless list of possibilites here) grand am's tend to make lots of weird noises from time to time.

[b2089]

It's under 50k miles, and it hasn't had any work. I didn't think it needed any either, the GM recommendations are rather vague.

I have had the oil changed, but it did it before. The oil came out clean so I don't think it's an oil issue (sort of rulling out the lifters). I've let people hear it and they say that I'm either imagining the noise or being paranoid. It was the old GA that was suspected of having a lifter problem with a similar but 10's louder noisem but I didn't let anyone work on it because it ran fine and made that noise most of it's life.

[rixGAphx]

Originally posted by b2089
...it's the sound that lifters make when they aren't lifting properly. It's a faint sound, ....
said knock very faintly when either going up a steep hill with the cruise on or accelorating moderately fast,..That is, indeed, 'knocking' that is spoken of so often in regard to cars.

The engine is under very heavy load, and there is something slightly wrong with your air-fuel mixture.
Under this climbing/accelerating condition, the mixture is igniting in each cylinder by itself, slightly before the spark intends for it to ignite.

Let your tank run close to empty, then put in a half-tank of Premium instead of your 'normal' 87 octane.
The higher octane is specifically intended to prevent knocking.

The GA's engine has a 'knock-sensor' to adjust the spark when it get close to knocking by itself, but your condition is slightly beyond that adjustment; or unaffected by it.

I would run a bottle of name-brand, off-the-shelf Fuel Injector cleaner through a tank of gas.
One or two dirty injectors could be causing a lean condition, and this often causes knocking.

IMO your plugs and wires shouldn't need attention until 100k miles.
But the plugs are aging slightly, as their metal tips are 'eroded' by the sparks.
Most GA owenrs see a slight mprovement in milage and 'pep' if they replace the plugs between 50k and 75k miles.

Wanna REALLY hear that knocking, safely?
Climb a spiral ramp in a parking garage!!
Sounds like a bucket of bolts in the trunk and scares the crap out of you, but a couple floors of rise won't hurt anything.

If the knocking is as faint as you describe, that others think yer nutz, then it might be that the computer is properly keeping the knocking at JUST the perfect point that the engineers determined was appropriate.

Good luck,
-Rick

[b2089]

Considering how I run the lowest octane I can find, that makes sense. It didn't occur to me that knocking was even possible on this car.

Now I'm curious, I'm going to run some premium in it to verify this.

[b2089]

An update. Prior to making the thread I tried using injector cleaner. I don't recall what brand but it was one of the 6 dollar name brands. I imagine they're all about the same anyway. It didn't seem to effect the noise.

After burning that out I refilled to a half a tank. Still the occasional knock. I was at McDonalds and thought my car sounded odd. I got home, popped the hood and I could hear a strange resonance. It was an off idle squeal. I have extremely sensitive ears by the way, it's a curse because places like Wal-Mart are so loud I get headaches from it. Anyway the squeal was off idle and the car was almost running rough.

Next, I put about three quarters of a tank of 93 grade on top of the 87 that was in it. Now the cars purring like a kitten and the squeal is gone.

Why does my car want higher grade gas? Did the injector cleaner cause that? Am I just overly paranoid about noises? I'm not going to keep giving it 93 by the way. If it runs better on mid grade it might get that, but I'm hoping to wean it down to 87 again. I'm told these cars learn and get accustomed to lower grade gas at the cost of performance. That's fine by me, I drive slow.