Pre-Detonation?
08-29-2010, 10:44 PM
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Pre-Detonation? Lately I've been hearing this "tick-tick-tick" when I'm going WOT. It starts to occur after 5,000 rpm's+ and it's pretty noticeable with the windows down.
A friend of mine that never rode in my car before picked it up right away. I've been putting 91 octane in it this whole summer. The car is also bone stock with 24,6xx miles.
Any suggestions?
A friend of mine that never rode in my car before picked it up right away. I've been putting 91 octane in it this whole summer. The car is also bone stock with 24,6xx miles.
Any suggestions?
08-30-2010, 02:32 AM
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Detonation, in my experiance, sounds more like marbles bouncing in a can than "tick-tick-tick". The noise you're describing sounds more like valvetrain clatter or exhaust leak.
Do you have access to a good OBD scanner that will show timing/knock retard? I would also look at fuel trims, misfires and O2 sensor readings when this is happening.
Do you have access to a good OBD scanner that will show timing/knock retard? I would also look at fuel trims, misfires and O2 sensor readings when this is happening.
08-30-2010, 07:51 AM
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Detonation, in my experiance, sounds more like marbles bouncing in a can than "tick-tick-tick". The noise you're describing sounds more like valvetrain clatter or exhaust leak.
Do you have access to a good OBD scanner that will show timing/knock retard? I would also look at fuel trims, misfires and O2 sensor readings when this is happening.
Do you have access to a good OBD scanner that will show timing/knock retard? I would also look at fuel trims, misfires and O2 sensor readings when this is happening.
08-30-2010, 01:20 PM
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Thing is, to actually hear continual detonation on a stock car would be somewhat rare and indicative of a problem more than just low octane fuel, since the knock sensors should be able to compensate for that.
That's why I'd want to hook up a scanner and look at basic fueling/exhaust/timing data.
That's why I'd want to hook up a scanner and look at basic fueling/exhaust/timing data.
08-30-2010, 01:37 PM
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Thing is, to actually hear continual detonation on a stock car would be somewhat rare and indicative of a problem more than just low octane fuel, since the knock sensors should be able to compensate for that.
That's why I'd want to hook up a scanner and look at basic fueling/exhaust/timing data.
That's why I'd want to hook up a scanner and look at basic fueling/exhaust/timing data.
08-30-2010, 07:53 PM
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The previous owner had them done at 16K miles. The car is at 24K miles now. Honestly, for a car that NEVER gets abused, get's driven on nice summer days, I dont see the big deal or why anything should fail yet.
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08-30-2010, 10:46 PM
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Seldom driven cars need special attention sometimes, to avoid certain problems that daily drivers don't see. For example, aging fuel gumming things up (like injector tips, causing poor fuel spray pattern - could be the reason for your issue). I had this problem last time I bought a seldom used car (the detonation was occuring at the first moment of WOT though, not at high rpms like yours). I cured it with a fuel system cleaning, and I now prevent it with fuel stabilizer and low doseages of continual-use cleaner.
08-30-2010, 10:56 PM
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also was your ac turned on at the time cuz i had the same problem with hearing ticking noise as i accelerate and it was my ac it started to tick louder with acceleration and would not be as loud at a idle
08-30-2010, 11:07 PM
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The A/C compressor clutch disengages at WOT, which is where his problem seems to be.
08-31-2010, 12:51 PM
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http://www.redlineoil.com/content/fi...ech%20Info.pdf
A few of our sponsors here sell this, or in my area you can find it on the shelf at Pep Boys. Since the initial clean up 6 years ago, I've been using a ratio of 1/5th ounce per 1 gallon of gas at every fill up (works out to 1 onuce for every 5 gallons). That's the manufacturer's recommended ratio for continual use. I also use Stabil with every fill up, at a ratio of 1 ounce per 2.5 gallons of gas.
Since doing this, I've never had a problem. On cold starts the engine fires so fast you can't even count the cranks, even after sitting for several months. And that audible knock problem has never returned. Last couple of years I've only driven the car about 300 miles a year, but it always starts and runs like a champ following my process.
08-31-2010, 02:22 PM
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When I bought my '98 car, the previous owner had put only 2000 miles on it in about 4 years. There was some knock at low rpm WOT, and also long cranking times on a cold engine start. I used Red Line SI-1 to clean the fuel system, initially using a full bottle for one tank. Here's the spec sheet incase you want to study the product:
http://www.redlineoil.com/content/fi...ech%20Info.pdf
A few of our sponsors here sell this, or in my area you can find it on the shelf at Pep Boys. Since the initial clean up 6 years ago, I've been using a ratio of 1/5th ounce per 1 gallon of gas at every fill up (works out to 1 onuce for every 5 gallons). That's the manufacturer's recommended ratio for continual use. I also use Stabil with every fill up, at a ratio of 1 ounce per 2.5 gallons of gas.
Since doing this, I've never had a problem. On cold starts the engine fires so fast you can't even count the cranks, even after sitting for several months. And that audible knock problem has never returned. Last couple of years I've only driven the car about 300 miles a year, but it always starts and runs like a champ following my process.
http://www.redlineoil.com/content/fi...ech%20Info.pdf
A few of our sponsors here sell this, or in my area you can find it on the shelf at Pep Boys. Since the initial clean up 6 years ago, I've been using a ratio of 1/5th ounce per 1 gallon of gas at every fill up (works out to 1 onuce for every 5 gallons). That's the manufacturer's recommended ratio for continual use. I also use Stabil with every fill up, at a ratio of 1 ounce per 2.5 gallons of gas.
Since doing this, I've never had a problem. On cold starts the engine fires so fast you can't even count the cranks, even after sitting for several months. And that audible knock problem has never returned. Last couple of years I've only driven the car about 300 miles a year, but it always starts and runs like a champ following my process.
08-31-2010, 02:59 PM
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http://www.streetrodstuff.com/Articl...ion/Page_6.php
^^^^^ Pretty good read^^^^^^There is a difference between detonation and pre-detonation/ignition. Pre detonation is MUCH worse but neither is good.....
^^^^^ Pretty good read^^^^^^There is a difference between detonation and pre-detonation/ignition. Pre detonation is MUCH worse but neither is good.....
08-31-2010, 03:53 PM
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Keep in mind though, we are still assuming that the noise is in fact some sort of knock/detonation. There are other things that can make similar noises, from internal/valvetrain chatter to even a loose spark plug.
Have you ever done a 3-1 downshift and mechanically over-revved? Or hit the limiter really hard? Bent pushrods are pretty common on the M6 cars, and can make noises like you've described.
Do you feel a drop off in power when the noise starts to happen?
Access to a scanner would help to narrow things down a bit. Too bad you don't know someone locally that has one.
08-31-2010, 04:53 PM
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Sure. It'll mix faster if you put it in before the fillup, but it'll still work fine either way. Actually, for my continual use pattern, I always add it after filling the tank, so I can use the proper ratio for the amount of gas I've added. But for your first treatment, just dump the whole bottle in there.
Keep in mind though, we are still assuming that the noise is in fact some sort of knock/detonation. There are other things that can make similar noises, from internal/valvetrain chatter to even a loose spark plug.
Have you ever done a 3-1 downshift and mechanically over-revved? Or hit the limiter really hard? Bent pushrods are pretty common on the M6 cars, and can make noises like you've described.
Do you feel a drop off in power when the noise starts to happen?
Access to a scanner would help to narrow things down a bit. Too bad you don't know someone locally that has one.
Keep in mind though, we are still assuming that the noise is in fact some sort of knock/detonation. There are other things that can make similar noises, from internal/valvetrain chatter to even a loose spark plug.
Have you ever done a 3-1 downshift and mechanically over-revved? Or hit the limiter really hard? Bent pushrods are pretty common on the M6 cars, and can make noises like you've described.
Do you feel a drop off in power when the noise starts to happen?
Access to a scanner would help to narrow things down a bit. Too bad you don't know someone locally that has one.
08-31-2010, 05:59 PM
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If this was knock/detonation, and it was bad enough to hear, I would expect some power loss from the knock sensors pulling back timing (which they certainly should be if you hear audible knock).
You can try the fuel system cleaning, as it can't possibily hurt and is cheap.
One other free thing you can try that's pretty easy is checking the spark plugs. You mentioned they were changed before, maybe they were not tightened enough and might have backed out over time. Compression escaping via a poorly sealed plug can make a tick like that as well.
And of course, always check for exhaust leaks.
Last edited by RPM WS6; 08-31-2010 at 06:05 PM.
08-31-2010, 06:10 PM
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I agree, if at all possibile you should get a scanner on there, especially with this in mind:
If this was knock/detonation, and it was bad enough to hear, I would expect some power loss from the knock sensors pulling back timing (which they certainly should be if you hear audible knock).
You can try the fuel system cleaning, as it can't possibily hurt and is cheap.
One other free thing you can try that's pretty easy is checking the spark plugs. You mentioned they were changed before, maybe they were not tightened enough and might have backed out over time. Compression escaping via a poorly sealed plug can make a tick like that as well.
And of course, always check for exhaust leaks.
If this was knock/detonation, and it was bad enough to hear, I would expect some power loss from the knock sensors pulling back timing (which they certainly should be if you hear audible knock).
You can try the fuel system cleaning, as it can't possibily hurt and is cheap.
One other free thing you can try that's pretty easy is checking the spark plugs. You mentioned they were changed before, maybe they were not tightened enough and might have backed out over time. Compression escaping via a poorly sealed plug can make a tick like that as well.
And of course, always check for exhaust leaks.
I also have a dying clutch....I've wondered if this may be related to that. Last but not least, when I put 94 octane in it last year, I never noticed this ticking?
08-31-2010, 06:20 PM
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I guess the most simple thing to try would be a return to 94 octane, just to see what happens. If that cures it, then you know what's going on. 
If you don't want to wait till the tank is empty, see if you can find some 100 octane unleaded (not sure what they sell in Canada). Add about 1/4 tank of that and you should see enough octane boost to equal 94.
Either way, if this issue is knock, then something needs to be cleaned or replaced, since the engine should run just fine on 91 octane. So the fuel system cleaning would still be in order as the first, cheapest step.
Also makes sense to check that exhaust clamp at the Y-pipe, make sure it's tight. Maybe have someone rev the engine while you're under there, and listen for a leak.
If you don't want to wait till the tank is empty, see if you can find some 100 octane unleaded (not sure what they sell in Canada). Add about 1/4 tank of that and you should see enough octane boost to equal 94.
Either way, if this issue is knock, then something needs to be cleaned or replaced, since the engine should run just fine on 91 octane. So the fuel system cleaning would still be in order as the first, cheapest step.
Also makes sense to check that exhaust clamp at the Y-pipe, make sure it's tight. Maybe have someone rev the engine while you're under there, and listen for a leak.