Strang Noise..

[1990_LX]

In our 95 GT there is a strange noise. I haven't had the time to check it out yet but I wanted to see what you guys think. When say the rpms are below say 1500 and your in a gear slightly too low and you give it gas, it slowly speed up(like you would expect it to) but it makes a strange kind of raddling noise. Obviously I don't drive around in 3rd going 20 with it punched but when you come around a corner /speed up/ect and it's really not nessicary to downshift it makes the noise. The only thins I can compare it to is like in every movie when a car dies it makes that clunking/raddling sound. That's as best as I can come up with. Any thoughts?

 

[MaximumRisk]

It could be pinging/detonating sounds like putting pebbles in a can and shaking it (rattle) it can be caused by bad gas, wrong timing, bad plugs, etc.

Are there any vibrations along with the noise?

 

[1990_LX]

No, vibrations. And I'm fairly sure it's not because of bad gas, I have gone through enough that it would have been flushed out. Also, the car is bone stock, the timing has never been changed. The only thing not stock is a set of Flows, which makes like 550 rwhp. Back to the topic.

 

[Quick281]

sounds like it would be a ping or something like that.... maybe the cats are coming apart ?

 

[1990_LX]

It only does it at lower rpms though...

 

[MaximumRisk]

what grade of gas are you using??
did it start making the noise after it started getting cooler outside?

 

[1990_LX]

Temperature hasn't seemed to make a difference. I have 89 in it now.

 

[Quick281]

try 93

 

[1990_LX]

You think it would make that much of a difference even with it 100% stock? I'll give it a try, it's almost empty right now. lol

 

[Quick281]

yes it really does make a difference

 

[1990_LX]

I've always heard from people that it won't net you anything and it in theory should run the same unless you had a solid set up. Anyways, I'll give it a try and see how it goes. Thanks for the suggestions guys.

 

[fiveohhfox]

yes it really does make a difference

yea i agree i had a 02 linlcoln ls v8 when i used any thing less than 93 it made that noise also

 

[MaximumRisk]

lower temperatures makes the air much denser which would require more fuel (or better fuel) or less timing to avoid leaning out the mixture too much. The stock computer/maf are supposed to compensate for changes in air temperatures, but apparently it is not doing so properly. Put some 93 grade gas and see if it helps

 

[1990_LX]

I'll probably do that tomorrow. Thanks again guys. Fiveoohfox, what color is that? You car is the same color mine used to be, but I'm not sure on the name, is is light or deep Titanium Metallic?

 

[1QWKVERT]

MaximumRisk hit the nail on the head.

You'll experience that with a 5L SD car in cooler temps. go for the 93 and see what happens.

 

[1990_LX]

Seems to help, I only drove from the gas station to my house but I got on it a few times and no pinging, thanks guys.

 

[toomanytoys]

MaximumRisk hit the nail on the head.

You'll experience that with a 5L SD car in cooler temps. go for the 93 and see what happens.

A 95 would not be SD. A egr valve thats not functiong properly will cause knock like that. Low rpm , light throttle knock is a sign that there is a problem elsewhere and the octane is masking it. That car should be able to run on 87 without issues.

 

[toomanytoys]

Could also be a bad tps.