Rattle under low rpm load
Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
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From: Somers Point New Jersey
Possible detonation? Need opinions PLEASE
Just yesterday I started hearing a strange metallic rattle under heavy-ish throttle at low rpm. Like 1500-2000 rpm. It seems to be more prominent when I shock the throttle (not stomp on it, I would never do that at low rpm), like if i put it at 75% throttle instantly. I am pretty stumped as to what is causing this noise. I really hope it is not a bottom end issue. My god, I can not afford that right now. It is load and rpm related and does not happen above 2000-ish rpm. I am wondering how long this problem has been present as I never use more than 25% throttle at such a low rpm because of my head/cam mods. Anyone have any ideas????
Last edited by Targa98; Jan 18, 2009 at 12:33 AM.
Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
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From: Somers Point New Jersey
yes, it does! Damn, so maybe I got bad gas!? I always use 92 or 93 octane. It is hard to find 93 anymore here in jersey. Man, I don't think my compression is THAT high, I think it was calculated to be around 11:1
Maybe I should just stay at a higher rpm then?
Maybe I should just stay at a higher rpm then?
Melting Slicks
Joined: Apr 2007
Posts: 2,787
Likes: 22
From: Lititz PA
Is this sound very pronounced or is it something you have to listen very closely for? I have a similar sound (I think) – sounds kind of like a tambourine. However, I can only hear it with the radio off while listening very intently.
Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
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From: Somers Point New Jersey
yes, it is rather hard to hear, my radio has to be off or down low and I wait to reproduce it when there are no cars driving by. I just got off the phone with my engine guy, he said detonation shouldnt occur at such a low rpm, that it would happen at WOT if anything and be most pronounced at my max torque rpm. If I feel brave tomorrow I may try WOT around 3000 rpm.
Burning Brakes
Joined: Aug 2008
Posts: 1,058
Likes: 91
From: Indiana
Because it started after I adjusted my catback. It sounds like exhaust it touching somewhere, however mine is not and all clamps are tight. Some have suggested the the spring mounts may be loose or a weld has broken on the cats. I havent been out in the cold to check that out yet. It only makes the sound when the car is warmed up, under a load, and between 1200 and 1300 rpms. Drives me nuts.
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Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
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From: Somers Point New Jersey
hmm, there are certain similarities that interest me. The rpms for one and the fact that it only happens when the car is warmed up. I believe that is the same as mine but I am not sure, i will double check with the car cold...
Thread Starter
Instructor
Joined: Jun 2008
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From: Somers Point New Jersey
Well, actually it is funny you say that because I have been meaning to pull everything behind my motor to check for a possible bad pilot bearing/torque tube bushing. I guess I will take it easy until I get a warm weekend to do that first. And hope for the best in the meantime.
Thread Starter
Instructor
Joined: Jun 2008
Posts: 220
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From: Somers Point New Jersey
