strange sound = worried man

[motor602]

I had my 01 RT out today and noticed a strange noise at WOT. north of 4K, there is a noticeable scratchy/rattly noise coming from the forward center console (perhaps even engine compartment area). I tried different gears at half throttle and ran the engine up to 4-5.5k, no noise. However in different gears (2-3) the noise is noticeable at WOT. It almost sounds like small pebbles rattling around in a tin can (possibly some loose rock salt that the rain didn't wash away?). Any ideas where I should start checking for anything abnormal? I realize my write-up is rather vague, but I'm not great at diagnosing problems with cars, I can only write up the symptoms ANY help is appreciated. Thanks!

 

[plumcrazy]

how old are the wires ? detonation sounds like that too.

id make sure the wires are all on correctly first, especially the rear ones based on your noise.

 

[motor602]

wires are brand new, just changed to AB's wires this summer. they've been on for about 5 months now with no issues. will definitely check to make sure all the wires are on tight.

I kept an eye on my VEC 1 at WOT and the ratio was correct (i.e. the first blue light illuminated). Does that add any additional information?

 

[motor602]

just pulled off the cowl and check all the connections at the power pack and at each cylinder. everything is attached tightly, no loose connections.

 

[Steve-Indy]

Loose flywheel bolt?

 

[jdeft1]

Could it be related to the vent fan? .. WOT = vent doors close, maybe rattle?... Strange.


How old is your gas? , From the description I think 'knock and ping'.... detonation. (same as Plumb).

 

[martyb]

It sounds like detonation. Is your engine NA or forced induction?

 

[motor602]

just filled the tank up last weekend. car is NA, only mods are VEC1, corsa, smooth tubes. as stated before, changed the plugs and wires this past summer, just checked all connections and nothing is loose. VEC1 shows a proper A/F mix. This is the first time I am hearing this noise in the 10 years since I have had the car.

 

[TP_ GTS]

Are you sure it's coming from the engine compartment and not from under the car? I had a similiar "Weird" rattle that sounded like what you described. I found it to be the heat sheild under the driver side rattling.

 

[Jack B]

Plumcrazy is probably correct, sounds like detonation. In general that will happen near peak torque (3700-4300) and will happen more readily in the higher gears. Those are all generalities, the exact timing advance could change those comments. If it is severe enough the white surface/plug insulator could have what looks like pepper on its surface. Two simple tests, put in an existing VEC program card to reflash the tune, secondly, if it is detonation you do not want to keep running it, pull the plugs and post a picture. Then again, you could have some weird resonant mechanical chassis/body vibration.

 

[SlayerLS1]

Marbles in a can usually means detonation. I'm hoping for your sake that we're all wrong.

 

[motor602]

guys, why would detonation start all of a sudden? what are possible causes? I am trying to wrap my head around the 'why now?' question.

I am going to pull the spark plugs tomorrow and will post pictures if anything looks abnormal. I'm guessing a discolored or peppered plug is a pretty good positive indicator, but not necessarily a great negative indicator?

 

[Dan Cragin]

There is a TSB to reprogram the engine controller for spark knock for your year model. Most likely it is worse now because this is the time of years they change from winter to summer fuel blend.

 

[motor602]

Hey Dan,

do you think reprogramming by VEC1 would do the trick?

 

[motor602]

ok, so i looked around on youtube to see if I could find a representative video. After searching through lots of videos for spark knock or detonation, this video seems to best fit the sound I heard this morning, only imagine it coming from a more badass V-10. Being that this video is entitled "detonation sound" I'm not feeling too great right now. What do I do to fix this situation?

http://www.youtube.com/watch?v=Due7mkTHMlw

 

[bbirch]

Burn as much gasoline as you can driving without allowing detonation, unless you can siphon several gallons out. Then get Premium from another source. Some stations fill their tanks with lower octane in winter to make more money and figure the colder temps will mask what they are doing. Have seen Premium only vehicles knock in January, February and March and be fine in the hot summer from one station. Grrrr..........

 

[forexx4]

Burn as much gasoline as you can driving without allowing detonation, unless you can siphon several gallons out. Then get Premium from another source. Some stations fill their tanks with lower octane in winter to make more money and figure the colder temps will mask what they are doing. Have seen Premium only vehicles knock in January, February and March and be fine in the hot summer from one station. Grrrr..........

Exactly what I was going to say. Either that, or throw in a quart of Torco Accelerator (the stuff REALLY works).
From their website: 5 gal. of 91 oct + 32 oz. Torco = 105 oct
10 gal. of 91 oct + 32 oz. Torco = 102 oct

 

[Red Snake]

As mentioned above, put in the octane booster. Doesn't cost a whole lot and you'll know immediately if detonation was your issue. If what you were hearing is not detonation, boosting your octane won't hurt anything.

 

[plumcrazy]

is the car down on power by any chance ?

 

[motor602]

I didn't notice any drop in power yesterday, still terrifies me when i punch it. Thanks for the all the direction guys, I'm definitely going to go get some octane booster and see if there is any change. The sound should still be audible at WOT in neutral correct? I don't want to have to go out and find a stretch of open road unless its necessary, would rather test in my garage.

 

[evomind]

I didn't notice any drop in power yesterday, still terrifies me when i punch it. Thanks for the all the direction guys, I'm definitely going to go get some octane booster and see if there is any change. The sound should still be audible at WOT in neutral correct? I don't want to have to go out and find a stretch of open road unless its necessary, would rather test in my garage.

not necessarily AT ALL. there isnt as much of a load on the engine while its in neutral. you can try the octane boost, but if youre getting engine knock you either got REALLY bad fuel, or something in the tune or elsewhere is off. in all liklihood you will need to get her on a dyno.

 

[motor602]

The plan is to:

1. run down the tank (only about 4 gallons left) under light load and put in the octane booster with a new tank of fuel. Then test.
2. if no resolution, reset the VEC1, then test.
3. if no resolution, pull the plugs and check SSx damage.

I'll post back with news / results.

 

[plumcrazy]

might wanna pull the plugs now to be safe, cheap insurance

 

[motor602]

So here's the update. Pulled the plugs and no clear signs of anything wrong. Put them back in, put in a pint of Lucas Oil octane booster and filled up with a tank of 93 octane. I went out for a test run and after about 7 miles on the new fuel, did 6 pulls to the redline and could not hear any pebble rattling / scratchy / detonation noises that I heard yesterday morning. Additionally, I kept an eye on the VEC and the A/F ratio read the 1st blue light at WOT. I will continue to keep an eye and ear on it, but I guess I can chalk this up to a crap tank of fuel?

 

[plumcrazy]

hopefully. keep running thru that tank and adding in good fuel

 

[motor602]

sounds good plum. Thanks to you and everyone else for all the help!

 

[forexx4]

Good to hear that!

 

[Jack B]

MOTOR602:
The VEC1 does not really give you an indication of true a/f, do not rely upon its lights to ascertain your a/f ratio.

 

[jdeft1]

I guess you just bought a tank of bad fuel..... it happens. If all was good untill you last filled up. ???

Bad gas could easily be moisture laden, low octane crap fuel. The result is engine knock/detonation under load. I'm guessin' it's fixed. Fingers crossed.

 

[motor602]

Jack B, duly noted, I wish I could get to a dyno. Hopefully soon.

jdeft, car has been running like a top for 10 years / 30,300 miles, not one hiccup. Filled up the tank last weekend with some Sunoco 91 and Saturday was the first time on that tank that I had the car at WOT. Either way, a pint of octane booster and 3/4 tank of 93 seemed to do the trick. Needless to say I'll be monitoring / testing for the next tank or two. If everything remains normal as it is now, I just thank my lucky stars and move on.