94-GT Rattle engine noise

SteveG94GT

Member
Aug 23, 2016
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5
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Hey guys, It has been a while since I posted, but I have a good one for ya. I am sure most that see the title of my post and might say spark knock. But I hope you will read on and see if you still feel that way. I have a 1994 GT, 5.0 automatic O/D.
I do get a rattle can noise from front end of car upon accelerator input, less noise if it is little input. Very little acceleration when noise is present, which is not 100%, maybe 95%. Only when the car is moving. Any gear, any RPM, if car is not rolling, it does not rattle. If car sits for a few days, sometimes it takes a few drives to start. Sometimes it happens in the middle of a drive. The initial part of a drive will be fine, but all it can take it a stop a traffic light or a location, and noise will start as car starts moving again getting up to speed.
My overdrive button does not seem to be working. It doesn't feel there is a detent at all when I press the button and no indicator light on dash. When car gets "hard" acc. input, and goes into a "passing gear" car picks up and rattle goes away. Until it shifts back into gear. I was thinking my overdrive may be going?
Could it be a problem with a cat? loose oxygen sensor? OD? I hear a lot about a loose heat shield or something like that, but why would that affect the way the car accelerates? If it is spark knock, and all the remedies I tried have not work, how do you fix it? I have tried a complete tune up, sea foam in the fuel and crankcase, high octane fuel for a month, still no change. This has been going on for two years with no change, worse or better.
If I need to add more info to help, let me know. Thanks guys.
 
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General karthief

wonder how much it would cost to ship you a pair
Mod Dude
Aug 25, 2016
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I doubt spark knock would last this long without engine damage.
From your description I'd say a transmission problem. But that's just a guess.
 

SteveG94GT

Member
Aug 23, 2016
18
5
13
50
I doubt spark knock would last this long without engine damage.
From your description I'd say a transmission problem. But that's just a guess.
Thanks General,
Since it seemed to be a power issue, I was leaning that way myself. Thanks for the input.