knock at idle..

[chad6159]

okay guys finally got my car back together. the belt that goes onto the oil pump broke causing a crazy mess. including messed up intake cam and camgear, 2 bent valves..ect. so we put it all back together for the second time. get the timing to where what we think is perfect and when you start it you hear a awful knockin noise if the rpms drop below 900. what could this be? its making us go crazy! when you rev it the noise goes away or if you set the idle to 1000 it goes away. any ideas?

EDIT: this happend after we were messing with the timing. we had the timing on it perfect but couldnt get the idle down past 1500 rpms.. so we moved the intake a tooth forward, got the idle down but now knocks like crazy

anybody?!?!

 

[gofer]

You need to set mechanical timing as per the Mitsu manual, advancing it a tooth like that isn't the right way to get your idle down from 1500.

Get your timing belt set correctly:

-Timing Belt Alignment
-1g Timing Belt Replacement​

Then set ignition (base) timing:

-Setting Base Timing
-VFAQ 1g Ignition Timing​

I'm not saying that by doing the above is going to fix your knock problem but atleast you'll KNOW that its timed correctly.

 

[MichaelSuch]

Where does the sound come from exactly? Is it from the block or head area? I had a similar problem when I rebuilt my motor. I had all new timing components, drove it about 60 miles with no problems at all then when I was driving back home I noticed the sound. It was a very loud knock and it seemed to go away about 3000 rpms. I ended up tearing the timing apart again and everything looked fine. It ended up being the exhaust timing gear being slightly loose. You couldn't even tell it was loose by looking at it while it was running. I even used red loctite on that bolt. I tightened it a quarter turn and it is no longer making that sound. Make sure everything is tight and that you harmonic balancer has no cracks and is not splitting too.

 

[chad6159]

everythiing is aligned perfectly now and now the idle is only at 500 and cant seem to get it any higher and it dies becuase the idle is to low and knocks like hell

i was in the car and the person that's helping me said it sounds like its coming from the vavle/head area. but we took the valve cover off and started it he said it sounds now like its down farther in like the lock area. the balance belt broke so could that mean the balance shaft could be broke?

 

[AlaskanDsm]

It might help if you post a video clip or a sound clip of the problem you are having. On our cars with interference motors, you don't want to mess with moving the teeth or forwards and backwards. Next thing you'll know you will being doing a build all over again.

 

[chad6159]

this is not my car but it sounds the same...when you have the valve cover on it sounds like something is tapping on the valve cover. but when we take the valve cover off and start it it sounds like its nower inside the engine. does the balance shaft idea make any anysence to anybody?

YouTube - Talon 6bolt First Startup

well just found out what happend. the timing belt came off which in turn bent valves and messed up my intake cam and cam gear. replaced all those and it knocks.

Present day: when we put it all back together we used the same timing belt because at the time we didnt think that was our problem. and it was just changed two months ago. so im going to try to buy a new belt for it and see if that fixes it becuase it had to get streched when it came off right? and if timing is off then it can knock. so thats my next step on friday, since tomorow is Turkey Day.

 

[chad6159]

anybody?!?!

update! we bought a new timing belt and slapped it on...it still knocks but runs alot bette. what could this knock be? the knock happens at alot lower rpms. (below idle) so what would that be?

 

[AlaskanDsm]

So you had all of the valves replaced and the head rebuilt?

Also, does the sound occur at every rotation of the cam shaft or the crank shaft? Take a ratchet and turn the crank and listen for when it knocks if you can and see where it is knocking. Sounds like it could be something like a rod knocking or maybe a busted piston/ Or maybe another bent valve hitting the piston.

 

[chad6159]

yeah we replaced the bent valves, and if it was a bent rod wouldnt the knock get faster when i hit the gas instead of going away?

 

[AlaskanDsm]

yeah we replaced the bent valves, and if it was a bent rod wouldnt the knock get faster when i hit the gas instead of going away?

Yea I would think so. I can't watch that video at work for a reference to sound but I have heard of issues where knocking can be heard only after a certain RPM and such. Wonder if it is something like a collapsed lifter when there is a lack of oil pressure?

 

[chad6159]

well it does have lifter tick a little bit but its alot louder than that...also was just driving it around and now it wont go into 3rd and 4th gear. what would that be has to be a cable right? but everything seems to be moving fine.

 

[AlaskanDsm]

I'm not too good at tracing these kinds of issues over the internet. One of those things that I'm better at in person haha.

Try referencing this tech article and see if it doesn't help to at least narrow down the possibilities.
http://www.dsmtuners.com/forums/articles-miscellaneous/337788-what-causing-irritating-noise.html

Outside of that, do a compression test just to verify but if the noise is 100% RPM related and not speed or gear related, I would say that the transmission could be ruled out as a cause (not including the shifting problem you are having), I would also find out if the knocking is occuring at each rotation of the crankshaft or the cam shaft. This will help point you to identify if its an issue with the head or block.

 

[dsmrollerz90]

It almost sounds like either your not getting good enough oil pressure to your head. It could also be your valves tapping your pistons... But then you would almost hear it constantly. Did you replace your oil pump? That might have also gotten damaged.

 

[DSMITHGSX]

do u have an oil press gauge

 

[chad6159]

just the stock one... i have an aftermarket, but it is not hooked up