Contour Enthusiasts Group Archives Forums General Troubleshooting Strange "ticking" noise at low RPM's.. HELP!?

I'm a car noob, and have never heard "knock" before, but I would guess this is it. I'm scared to death its something serious. Here's my story:

Filled up with gas at 4:30pm at SpeedWay. Drove about 1.5 hours from Lansing to Mt Pleasant doing about 90 or so MPH (so 4k rpm's steady the whole way). Stop and eat at Bennigans. Start driving north again for 1.5 more hours until I get to Gaylord. Stoping at the stop sign at the end of hte off-ramp, I let the RPM's drop to idle and there is a LOUD ticking/knocking noise from my engine bay, I mean it sounds REALLY bad. But the engine feels fine to drive. No loss of power, and the ticking/knocking goes away above 2500 RPM's, it completely smooths out and sounds perfect.

Anyway, I'm freaking. So I get it up to Boyne Mountain, about 15 minutes later, and turn the car off for a few seconds while I run in to take a piss, and look under the hood. Everything passes visual inspection, oil level normal. Start the car up, and now it only knocks/ticks below 2000 RPM. Ok, so I need to get home, and at highway speeds RPM's are above 2000 anyway, so I figure I'll be fine. I get it home, turn the engine off, go inside, go back outside, start her up, and now she only does it below 1700 RPM. wtf?

I tried listening to where the knock is coming from, seems to be under the front valve cover from best I can tell, its just so freakin loud.

Guys, I'm a noob, have no idea what this could be, and I'm scared sh!tless its a spun bearing or something. I really don't want to dump a grand or more into this engine, I was hoping it'd last another year or two before I have to do that... What could this be?

Isnt there anyway you can copy the noise and then post a link to it?

Ticking doesnt really mean to much, could be anything, bearings,lifters, anything.

my car makes a knocking sound during low RPM, think its just because of the hydrolic valve lifters and stuff... but mine is only when cold

Well I've always had a very faint ticking noise, but this time its just scary how loud it is. I mean, you almost don't want to stand near the engine its so loud.

I'll see if I can't get a sound sample later today for you.

Do you think it's safe to drive? I have to make a 100mile trip today

In my opinion I dont see why you couldnt drive it. I know someone who had lifter nosie and they drove it, just got louder by a bit.

Its up to you man.

I had similar ticking, first it was from 2k up to 4k but it would switch around a bit sometimes. Starting at 3 instead of two etc. I'd heard knocks before but I didn't think that's what it was. Ended up being totally fried bearings and a bad valvespring, not sure which was actually clicking. Mine took 4 months before it gave out so even if that's what it was you might be ok to drive. I wouldn't, and if you do be very gentle until you know for sure.

Just a thought, has your engine got good clean oil of the right grade and up to the correct level, possibly this noise is dut to an hydraulic lifter blockage, they have very small oil passages that can clog if the oil bacomes dirty.
If you put the handle of a screwdriver against your ear and touch the buisness end on various parts of your engine in the general area of the noise, you should be able to narrow down where the noise is coming from, this may give some clues, please be careful to avoid rotating parts with hair clothing etc and spark plugs/wires with metal objects, we dont want to add any more noises
Good luck
James

Well, its gone (!?!?!?!?). Maybe bad gas? After filling up again today at Mobil with good old 93 octane, drove it to Alpena and back (about 220 miles round trip) and well, its gone. No more knock.

I did get this sound clip of it this morning before it went away. Sorry for poor quality, it was taken with an MP3 player from my drivers window:

click me

Note how it smooths out above about 1100 RPM this morning. Each time I turned off the car, it would only make the noise at a lower RPM.

I am running a superchip which advances my timing, so I'm assuming poor gas would probably cause it. Sound right?

EDIT: It does, however, still idle like crap. Not a strange noise, but it sits there and stumbles all over the place. Could the bad knock have maybe fouled a plug (I don't know what that means, but seems like it would cause bad idle)?

Well, its back. Filled up at a different Mobil station today though. But the loud knock is bad at low RPM's. What gives?

I have a CEL, its the usual "IMRC stuck open" so I have a new IMRC ready to go in to replace it, but I've had that CEL for a month or so now and am just now getting this knock.

Should I ditch my Bosch +4 plugs too for some autolites?

I'm really lost, my car sounds like crap. What would cause this knock?

Ok here�??s your problem.

Your car has been feed a steady diet of 93 octane gas which combined with short trips has lead to carbon build up. This explains your bad idle and your knocking noise after your long trip.

What you experiencing is a �??carbon ring�?� at the top of one (or more) of your cylinders. It was formed after your long drive at high speed. When you shut your engine down the carbon broke loose and got trapped in the top of the cylinder at restart. When the piston hits the ring it makes a sound like a bad rod bearing. At higher RPMs the sound is masked so you don�??t here it as much.

How to fix it.

1) Use the correct octane (for a standard compression contour that�??s 87).
2) Have the engine de carbonized at a shop with the correct equipment.

Remember this simple rule high octane gas is for high compression engines. You are getting lees performance and spending more money using so-called �??high test�?�. The �??high test�?� gas will not burn at a high enough temperature in a standard engine to burn completely, leaving behind the carbon that is causing your problems.

jeff