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Knocking? Weird though...

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Old Sep 27, 2007 | 12:26 AM
  #1  
Bullydawg's Avatar
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From: Alamogordo, NM
Car: 88 Formula 350
Engine: 5.7
Transmission: T-56
Axle/Gears: 9" 3.89
Knocking? Weird though...

When I start my car is knocks and runs rough, but when it knocks, I can feel the throttle pedal knocking back. So It was running wierd, and clicking, sounded like a spark plug wire undone. Then, the throttle pedal would click back and I could feel it hitting my foot. Then I replaced the starter (went bad) because it wouldn't start. now It started and it knocked like crazy and I could feel the pedal slapping my foot. I dont think the internals are messed up because the engine only have 12,000 miles on it. It is weird. If anyone knows anything or has any suggestions to check, please let me know.
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Old Sep 27, 2007 | 11:03 AM
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From: Littleton, CO USA
Car: 82 Berlinetta/57 Bel Air
Engine: L92/LQ4 (both w/4" stroke)
Transmission: 4L80E/4L80E
Axle/Gears: 12B-3.73/9"-3.89
Weird knocks are often related to the flexplate/torque converter, flywheel/clutch, or harmonic damper. The flexplate/flywheel items due to loose bolts, the starter going bad makes that a little suspicious. The damper could be a loose bolt, but also slipped ring.

But, if it is running rough, most likely you need to figure that out first.
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Old Sep 27, 2007 | 06:56 PM
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From: Alamogordo, NM
Car: 88 Formula 350
Engine: 5.7
Transmission: T-56
Axle/Gears: 9" 3.89
Re: Knocking? Weird though...

Okay, I will definitely check those out. Thanks. Anyone else have other idea's?
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Old Sep 27, 2007 | 10:28 PM
  #4  
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From: Alamogordo, NM
Car: 88 Formula 350
Engine: 5.7
Transmission: T-56
Axle/Gears: 9" 3.89
Re: Knocking? Weird though...

Okay, definitely the engine knocking unfortunately. It shakes, doesn't want to run, and the throttle pedal twitches. Any idea's it makes a kank kank kank sound. Sounds and feels like the piston is hitting the head. Any way to tell without taking it apart too much? Feel free to ask questions. Thanks for the help in advance.
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Old Sep 27, 2007 | 10:38 PM
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Car: 91 RS
Engine: 350 vortec
Transmission: T-5
Axle/Gears: not the best not the worst
Re: Knocking? Weird though...

have you checked the flexplate-TC bolts and the like?

who knows you might have stacked a rod bearing and are now playing tag with a head... if that is what you suspect obviiously stop running the engine and start tearing the engine down
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Old Sep 27, 2007 | 10:41 PM
  #6  
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From: Alamogordo, NM
Car: 88 Formula 350
Engine: 5.7
Transmission: T-56
Axle/Gears: 9" 3.89
Re: Knocking? Weird though...

Haven't checked, but I dont think it is it. I tried to wiggle it and nothing happened.
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Old Sep 27, 2007 | 10:50 PM
  #7  
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Car: 91 RS
Engine: 350 vortec
Transmission: T-5
Axle/Gears: not the best not the worst
Re: Knocking? Weird though...

well you always have the option of taking the engine apart... but you will be really pissed if you dont find anything.

how did this start... you walk out one morning and fire it up and it was there or where you hammering down and when you got off the throttle you noticed it was idling screwwy?
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Old Sep 27, 2007 | 11:25 PM
  #8  
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From: Alamogordo, NM
Car: 88 Formula 350
Engine: 5.7
Transmission: T-56
Axle/Gears: 9" 3.89
Re: Knocking? Weird though...

I was running late to school and so I drove my car. Not driving hard or anything. It started clicking and the petal kinda twitched. Well I didn't want to chance it and Parked it and walked. I come back and it wouldn't start. It would Go Click and then I would have no power. So I replaced the starter ( Dad informed me that the spare doesn't line up with the flex plate correctly) and it started up and ran like crap. I think I will switch the starter back and see if it works. If not, I will take off the oil pan and valve covers and go from there.
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Old Sep 28, 2007 | 07:58 PM
  #9  
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From: Arab, Alabama
Car: 1988 Trans Am GTA
Engine: 350 4BBL
Transmission: 700R4
Axle/Gears: 3.27
Re: Knocking? Weird though...

Originally Posted by Bullydawg
....I think I will switch the starter back and see if it works. If not, I will take off the oil pan and valve covers and go from there.
Shoot a video and post it so we can hear it. Ya got some mighty good ears in here...
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Old Oct 2, 2007 | 10:43 PM
  #10  
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From: Alamogordo, NM
Car: 88 Formula 350
Engine: 5.7
Transmission: T-56
Axle/Gears: 9" 3.89
Re: Knocking? Weird though...

I honestly dont want to start the car again. I will start to take it apart starting with valve covers, then oil pan.
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