Exhaust Vibration or Detonation?
Thread Starter
Heel & Toe
Joined: Aug 2002
Posts: 23
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From: timmins on
Exhaust Vibration or Detonation?
I'm not sure exactly but when I go WOT from around 50MPH I seem to get a noise like vibrating heat shields from somewhere? Or is it detonation from the engine? I'm having a hard time figuring it out cause sometimes it's there and sometimes it's not. I've tried 91 octane fuel but it didn't really seem to matter vs the 87 I usually run. I heard something about the vibrations in the exhaust fooling the knock sensor into retarding the timming? I know everything from the cat back is secure as I've just replaced and tightened everything...Anyone ever hear of similar problems? Car seems a bit sluggish at low RPM and the vibration/detonation is much worse at around the 1200-1500RPM...I'm usually in D around town as the AutoTranny wants to go to OD too soon for my liking...and the engines apparently...But once the RPMs get higher like over 2500 the noises seem to go away and the car seems to pull pretty hard...Oh well it's still a blast to drive...Thanks for any help...I'll definetly bang around next time I'm under the car for the loose exhaust components...Cheers Dave :chevy
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
Re: Exhaust Vibration or Detonation? (black88con)
It sounds like you may be getting ping.
A scan tool will tell the story; or you can turn base timing back by say 4deg for a test.
A scan tool will tell the story; or you can turn base timing back by say 4deg for a test.
Instructor
Joined: May 2003
Posts: 203
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From: Largo FL
Re: Exhaust Vibration or Detonation? (black88con)
I have an 85 4+3, and get a similar vibration noise at lower rpm's as well, 99% of the time in first gear, 1% in 2nd, and 0 the rest. Been trying to pinpoint it without really trying. My girlfriend thinks it may be the insides of the cat have corroded or something, and they could be rattling. The sound does dorta sound like it's from the cat area, but I dunno. You may wanna check your cat though. I'm interested in the source, but you'll be addressing this way before I get to it. Let me know what you find out. :lurk:
Kirk :seeya
Kirk :seeya
