Ok, here it is:

I have a 1998GT w/ 56,000 miles on it... It's been running fine.

It happened the other day..can;t remember if it was after a fillup or not, but no more than 2 days after filling up the tank that it happened.

It sounded like a loose piece of exhaust, as the almost rattling noise went up w/ the rpms... jacked up the car...nothing hitting the DS...nothing loose. STILL HAPPENED! It sounds like something loose right in/behind the engine compartment now. It only happens at low rpms while accelerating and at idle.

Is this a knock? A ping? What can it mean?

I put some 94 octane in it to see if that would help, but I could only fit 3 gallons. Any ideas?

P.S. Side note, is it normal for my auto tranny to make kind of a puffing noise when going into drive? Only noticeable w/ the car on w/ the door open...


THANK YOU GUYS FOR EVERYTHING!

 

don't know about the AOD-E trannies. it could be a loose heat sheild but it could be a bent rod or something worse. i would get it checked out before the pistons go into orbit. i think one from my first car is still up there plottin' on me

 

Take a screw driver and hold it over each cylinder on your valve covers, pinpoint the noise.

If it doesn't sound like it's an engine knock, look into your torque converter. They are known to become loose and trick people into believing they have a rod knock. Also, flexplates (flywheels) are known to chip and make a nasty knocking noise.

 

hey man what kind of octane of fuel are you using? I am thinking youre car is pinging, Its caused by a low octane fuel, my car pings on 87 octane, But on 89 very little ping, if youre engine is knocking thats caused by lack of oil changes, 1998GT w/ 56,000 miles only that kind of miles on it, I dont think its knocking, try using 89 octane on youre next tank of gas see if that helps.

Goodluck.

 

A '98 has a knock sensor. If it was pinging, it would retard the timing so fast that you more than likely wouldn't hear it.

 

Shop time........ sh*t..... As soon as I want new gears I have a repair bill to foot.

 

if this is an automatic..check trans fluid...check oil...put a can of 104 in the gas....if that's not it ..it may be piston slap which 4.6 is famous for early in the 4.6 run

 

or your engine is going. i ignored it in my corolla and almost got killed.

 

Sounds to me like a bad catalytic converter. Sometimes, they'll break apart and the catalyst chunks will rattle around in there. It happened to me and my first thought was 'oh Shat', there goes something REALLY expensive like the crank. Don't know if it's it or not, but mine sounded like two monkeys under there beating things with a pipe. This was with my old 94 GT.

 

wait, ignore my above post, I saw that you have a magnaflow X pipe. It still might be it if it's catted. I have no other ideas.