1996 thunderbird 4.6 v8 knocking noise on first startup any ideas?

[nurturantquasar]

so my 96 thunder bird has started having a quite loud knocking noise coming from the engine bay when i first start the engine after its sat for awhile like over night or through school. it gets faster with the rpms but its only like 2 or 3 seconds when it revs up a bit after i first start and then the oil pressure reads and bounces around for a bit and then it sounds fine and oil pressure is steady and good. ive noticed there might be a small loss in power like i cant spin the tires when i floor it anymore it just kind slowly lumbers off the line until it hits higher RPM. ive watched videos on youtube i dont hear anyone's thunderbird making that noise on startup. What could it be? is it Normal? Maybe a bad oil pump at worst? i just bought a new exhaust system and cold air intake so im hoping its nothing major. ive never heard this in any of the previous 2 cars ive owned and i cant tell where it comes from because theres only one of me.

also some things i found awhile back when i first bought it. it was a one owner car the guy i bought it from bought it new a long time ago 1. the spark plugs seemed like they havent been changed in years and it had the completely wrong size of oil filter it was way to small. so i dont know if either of those could of contributed to the knocking i hear now or not.

 

[Ford1]

so my 96 thunder bird has started having a quite loud knocking noise coming from the engine bay when i first start the engine after its sat for awhile like over night or through school. it gets faster with the rpms but its only like 2 or 3 seconds when it revs up a bit after i first start and then the oil pressure reads and bounces around for a bit and then it sounds fine and oil pressure is steady and good. ive noticed there might be a small loss in power like i cant spin the tires when i floor it anymore it just kind slowly lumbers off the line until it hits higher RPM. ive watched videos on youtube i dont hear anyone's thunderbird making that noise on startup. What could it be? is it Normal? Maybe a bad oil pump at worst? i just bought a new exhaust system and cold air intake so im hoping its nothing major. ive never heard this in any of the previous 2 cars ive owned and i cant tell where it comes from because theres only one of me.

also some things i found awhile back when i first bought it. it was a one owner car the guy i bought it from bought it new a long time ago 1. the spark plugs seemed like they havent been changed in years and it had the completely wrong size of oil filter it was way to small. so i dont know if either of those could of contributed to the knocking i hear now or not.

Funny you should bring back such fond memories! I purchased a 95 Bird in 96 with 13k miles. A few months before the end of the warranty period (and 34k miles), I got tired of hearing the same start-up knocking that you are talking about. I took the car to my dealer and had to leave it in their lot overnight so the service manager could hear it. I had left it there prior to that and no one could ever hear what I heard!
Long story short, they said that it was a rod knock. Ford opted for short block replacement and a week later I had a new engine. Two or three months later, I started to hear the same knock on start-up and it continued for the next 40k miles until I traded the vehicle. Since then, I have purchased a 1999 F-150 with 189k miles and the start-up knock already there. The truck has 203k miles now and runs great (albeit still with the knock at startup). I think that it is something that is common to many 4.6 engines during that period, but apparently not problematic.

 

[Jradford6387]

The loss of power has me wondering. If it speeds up with rpms that's never a good thing. If it's a rod or something of that nature though it's not just going to disappear after its warmed up. I'd have to say a knock can often be misinterpreted for a tap which could indicate valve issues maybe. With these overhead cam motors though who knows. The loss of power is truly concerning though. I'd say stop trying to bust tires loose before you throw a rod or cause serious damage to it and have it checked out by someone with a little more expertise with this particular issue.