Cold start tapping/knocking...uh oh....

[Figit090]

Every other time I start my supra I notice a knocking sound coming from something in the engine bay...probably the engine... but it's getting me worried...

This only happens sometimes... and after about 3 seconds it'd gone, but sometimes it hits hard enough to feel and i just dont like it at all....

I have noticed the noises when the startup idle does NOT go to 1k+ rpm but immediatly sits around 500, usually after i go shopping and my engine for one reason or another doesn't need to rev up...

...on cold days or when it hasn't been started for a night it will rev up to around one grand like normal and i dont notice any knock...i tried to slow the revs by letting the clutch slip a bit to see if i could hear it but i didn't notice anything (bad idea probably...but i really wanted to know if it always did it)

i hope this isn't an expensive problem... i've searched and came up with little on what this could be...rod knock? i've owned it maybe 2 months now and it didn't do this before.... and i have MORE than enough oil..it's above the full mark.

 

[Figit090]

nobody?

 

[IJ.]

Might be a bit tired and loose so the pump can't get enough suction/provide enough pressure when it starts at 500 rpm the clatter you're hearing is the rod bearings slowly destroying themselves.

Bit of a problem here do you hold a little throttle so it doesn't idle slow putting some extra load on it and maybe doing additional damage or do you let it idle slow clacking with minimal load.......

 

[Figit090]

well when it it's started and doesn't rev up past 600 or so you can hear the knocking, and it soon goes away.......

i'll go start it and see what i hear...

 

[Figit090]

nothing... i didn't notice the knock like it did for a few days... i'm hoping its not a bearing... on the first few starts it held an idle at around 1300 rpm. I let the clutch out to slow the rpm but i didn't hear anything wrong...i guess that's bad...i dont know.

I've heard the knocking sound when it starts up and doesn't idle fast, either from heat soak or because it's still warm from the last time i drove it (usually after shopping) it's only done it about 5 times that i remember... I'll start it and it will run at or a bit below the normal warm idle speed and it knocks (less than 10 times) and then sounds fine...

i was thinking (or hoping rather) that it was just a pump that needs more RPM's to run smooth and that was just making the noise... because wouldn't the noise be apparant all the time if it were a bearing?

I let it warm up a bit and probably started it 15 times to see if i could hear it...but nothing. If i'm going to hear it, it probably won't happen unless i run it for a while, shut it off, let it settle for a while, and then start it again.

what does a knock sensor do? does it sence bad timing?

 

[s383mmber1]

knock sensors will retard the timing accordingly.

Maybe your lifter need to be adjusted---but i didn't really read

 

[Figit090]

knock sensors will retard the timing accordingly.

Maybe your lifter need to be adjusted---but i didn't really read

yeah...um....thanks.

I guess if you didn't read then there is still no telling what could be wrong but i guess i'll take that into consideration...

for all i know it could be a cylinder not firing. :icon_conf

 

[jtamulis]

after youstart your car up, see what the oil pressure is at idle. if its really
low, change your oil to 20w50. Then see if it keep doing it. email me directly
with results. (and post here)

Jeff

 

[johnathan1]

i have heard of this, it has to do with the cams, and the tiny oil passage in a cam lobe being clogged or something, I remember reading this somewhere, and I have also heard the sound you described in person while I was shopping for supras... I am willing to bet SERIOUS money that this is the problem.... I will try to do some additional research...

 

[ddmcse]

i'm assuming you are open to suggestions .
here is mine

loose main pulley bolt

before you start the engine put your hand on the alternator pulley and give it a twist to see if it moves to the left or the right . you should not be able to move it..

 

[Figit090]

i have heard of this, it has to do with the cams, and the tiny oil passage in a cam lobe being clogged or something, I remember reading this somewhere, and I have also heard the sound you described in person while I was shopping for supras... I am willing to bet SERIOUS money that this is the problem.... I will try to do some additional research...

thanks! scared the crap out of me when you put "SERIOUS" and "money" in the same sentence but after re-reading it doesn't sound so bad.... thanks very much, i look forward to seeing what you come up with...i'd search a bit right now but i have schoolwork keeping be too busy...:icon_evil

i'm assuming you are open to suggestions .
here is mine

loose main pulley bolt

before you start the engine put your hand on the alternator pulley and give it a twist to see if it moves to the left or the right . you should not be able to move it..

By left or right i assume you mean sliding up and down whatever shaft it's on... so i'll go wiggle it and all the other pulleys i can get to and see what i come up with, just incase. thanks. and i am open to suggestion, although johnathan seems to be pretty confident of his diagnosis...but i'm willing to try anything!
----------EDIT----------;
Thanks to you i discovered my carelessly left-off oil filler cap... before starting. i must have had it running with it off for a little bit but thankfully i didn't drive anywhere yesterday and put it back on before loosing it... sheesh.

I wiggled every pulley and the only one with noticable play that i could move was the pully to the left on the bottom with the holes in it, which i believe is the power steering pump... and the whole shaft seemed to move, not just the wheel, because the bolt looked pretty well attached to the pulley and i think it's just armature play...not much either. When you said alternator pully... which is that...the pully on the alternator or at the other end of the belt? the alternator seems fine. The only thing i notice that i think is a bit odd is the main pulley, with the multiple belt tracks, has a slight wobble, not much but it's not running true like the other pulleys. maybe it's the size...i'm not sure. if this is abnormal i'll see if it's loose with a wrench later... let me know.

after youstart your car up, see what the oil pressure is at idle. if its really
low, change your oil to 20w50. Then see if it keep doing it. email me directly
with results. (and post here)

Jeff

--------EDIT----------
I started it up and it took about 5 seconds to get up to 40, and on my gauge that's the high point for idle, and midway in normal driving... when i had my head under the hood i gave it some gas to listen to the engine and that was enough to push up the pressure more so i think it's good. I drove it around my yard a bit and it never went higher than the next marker before the 80 mark... so i think oil pressure is fine.

 

[ddmcse]

inside that main pulley there is a bolt.
you can stick your fingers in there and see if you feel it and you can tell if it's loose. that main pulley should not be wobbling . if it's wobbling it would suggest it's loose , not good and that will make an engine knock sound when you go to start it when cold and it needs more than one crank to start .
if that bolt is loose you may have damage to the crank shaft.
i saw a post one here a few days ago about this issue
do not stick your fingers in there while the engine is running
grab that main pulley and turn it clockwise and/or counter clockwise instead of the fingers into the pulley if you would rather .
it should not move not even a pinch

 

[Figit090]

suck my fingers in, no looseness
tried to wiggle and turn the main pulley....no movement...period.

i think that it may just be made a bit...off and isn't as perfectly round as the other pulleys.

 

[supramacist]

What year model of car is this?

 

[Figit090]

1986.5..... mkIII..... 7mge

 

[NDBoost]

that would be cool if my car has this same problem. What about what someoen else suggested, not enough oil flow so you get a bit of knock until it starts flowing oil? Bump im curious..

 

[Figit090]

what would actually be making the knocking sound? the oil pump turning over? (i don't know how they work)

it hasn't been as prominant as it was for a few days but i still hear a faint knocking that goes with the engine rpm...it's just that my car usually revs up when it starts... so the lower idle knocking hasnt had much of a chance to happen..

but right now my oil pressure seemed a bit lower than usual, but i just now started looking at it so maybe it's been that way all the time...it's just that i drove it a bit harder than normal and the oil pressure didn't go up like i would think....maybe it was because it's warm and flowing better than when i cold start it.... that's probably it.

today my battery cable (which was poorly attached) came off after refuling and i got a nasty scare when i turned the key and absolutely NOTHING happened.... but i fexed it, drove it home and then made a permenant fix...now it's running a bit better and the ECU seems to have reset because it ran like it was really rich for a while.... gettin' better though... :biglaugh:

 

[IJ.]

Low to no oil pressure at start up lets the Rod bearings contact the crank and you get noise.
(see my first post in this thread)

 

[Figit090]

is that really bad?

 

[IJ.]

Can be if that's what it is!

Try the 20w/50 thing Jeff suggested if it stops making the noise on cold starts it's a good chance that Rod Knock isn't far off.