Loud knocking/rattling noise on startup?

[JLPM]

As Soon As I Start Up My 91 Turbo It Makes A Deafening Knock Noise. Any Ideas Of What It Could Be? Also, When It Is Off And In Drive It Will Roll Back Like It Is In Neatural..

[free5ty1e]

Could be valve tap; our valvetrain can be very noisy (tap / clack) when starved of oil. I dont know that I'd call the noise a knock but it can be quite loud.

Are you a quart or more low on engine oil?

As far as I know, an auto trans has no way other than park gear or brakes to hold on a hill when the engine is not on. Much different than leaving a manual trans in gear.

Sent from my SAMSUNG-SGH-I337 using Tapatalk 4

[rallyak]

The engine noise could be main knock, which is common on 2.5d engines. My moms has been making that noise for years but no problems in the last 500k. It's only makes the noise when cold every morning for about 2-3 seconds, after that no noise for the rest of the day.

[wtdash]

The engine noise could be main knock, which is common on 2.5d engines. My moms has been making that noise for years but no problems in the last 500k. It's only makes the noise when cold every morning for about 2-3 seconds, after that no noise for the rest of the day.

This is also called " piston slap ".
TD

[wtdash]

As Soon As I Start Up My 91 Turbo It Makes A Deafening Knock Noise. Any Ideas Of What It Could Be? Also, When It Is Off And In Drive It Will Roll Back Like It Is In Neatural..

As noted above - Check your engine oil level. Probably low. Although it's not likely based on your description, I'd also check your heat shields on the exhaust as they can rattle.


GL,
TD

[rallyak]

Main knock only presents is self until oil press come up.

Piston slap is present when excessive or large clearance between piston and cylinder (common on forged pistons because of how much they expand, thats the way they need to be set up) tell engine temps come up. In my car I have excessive clearance and can hear it even when the engine hot at a certain RPM.

[JLPM]

THe Car Is Undrivable With The Knock, Its Not Like A Small Knocking Noise, Its LiKe a Bulldozer Next To Your ear

[alexandermf]

^sounds to me like you need a new engine man.... That loud and not driveable? don't need a subie guru to finalize that had news