I just bought my first firebird. It's an 85 trans am with the automatic transmission. On startup, most of the time it has this loud rattle that goes away after a few seconds. A similar sound happens when I shift into reverse, though it only happens for a split second. My dad says it's maybe a bad hydraulic lifter, but I don't know. Any thoughts?

 

when I hear rattle I think heat shield

 

It's very loud, somewhere between a rattle and a knock, definitely coming from either the engine or transmission.

 

whats your oil presure like?

 

I know it sounds somewhat far fetched , but , I have seen a slightly loose torque converter cause such a knock . It seems that the bolts were just loose enough to cause a sound when it was started from stone cold , but after warming up the natural expansion of warm metal was enough to keep it just tight enough to not make a sound . Let it cool off , and the noise returned . The car's owner was CONVINCED it was a "rod rap" , so much so that he sold me the car for $500 , and 20 min work of dropping the torque converter's dust shield , putting some locktite on the bolts , and then putting the cover back , solved the issue ! (sold that now quiet running 2nd gen for 4K !!!! )

Now , im NOT saying for sure that this IS your problem , just giving you ideas of easy things to check before ripping into the engine to find it .

Can you imagine how embarassed you would be to take the engine apart , only to find loose external bolts that could be fixed in 20 min ????

Good luck with it , and please post results of your findings ......

 

I appreciate that suggestion. My oil pressure runs about forty psi from the looks of it, but the gauge or sender seems to be faulty. It'll read around fourty, then jump off the high end of the scale, sometimes dropping back to around fourty. I had a guy suggest putting some kind of an engine cleaner through and changing the oil, and also changing the transmission fluid and filter to see if that helps before taking any drastic measures.

 

Okay, so I've had some time to delve into this more. There may be a number of problems combining, but we'll see. When I drove the car last it had the knock sound worse than before, and when I stepped on the accelerator the engine would rev, then drop 400-500rpm or so, then come back up to 'normal' The oil pressure is steady at 40psi or so. Then when I went to put the car on ramps the rpms would drop and the engine would nearly die half way up the ramps. I ran some seafoam through the oil and then changed the oil. I also checked the torque converter, spark plugs, choke, and timing. The timing seems way off, but I don't know if I checked it right as this is my first carbureted car. If anyone has any suggestions, I'm at a loss. I also noticed that the car starts and runs at around 1000rpms, but after a few seconds it drops to 500-600 and starts the rattling. But when my dad opens the hood the rpms jump up a little again. He and I are both baffled.

 

first thing to do it get the timing right. and then go from there