hey all.
so i got my car back in the fall, put some hard IC piping on, got all tuned up, and check for boost leaks and she was solid.

sometime during the winter is starting idling kind of funny, especially when it was really cold, like 15 or below. would almost stall sometimes when coming up to a stop. i was assuming this had something to do with the tuning and kinda put it off til it got nice out, hoping with the warming air it would go away. now that it is nice out it doesnt want to die an idle, but instead bounces consistently between 900-1100 in about 2 second intervals. got kinda fed up today at work, and popped the hood to look for easy vacuum leaks. didnt find any off the bat, but i did hear a very weird metallic rattling noise coming from, what seemed to be, under the valve cover.. or behind the engine near the intake manifold.

not sure if these are related or not, but the rattle scares me, as it sounds like what i would think a loose cam would sound like, although if it were that, it seems the cams would have shredded themselves by now.

any ideas on both problems, and if they are related?

back to the web for more research...
thanks!
matt

 

should mention, that the rattle is VERY faint... but sound exactly like this clip...
http://www.youtube.com/watch?v=kUncpwkYTQ8

he enhanced it in this clip... its not nearly this loud, but this is the same sound:
http://www.youtube.com/watch?v=QNzb0U-467c

it comes and goes too... not constant like the lifter ticking. im used to that noise

 

Don't know about your idle problems, but you can use a screwdriver or pry bar as a stethascope. YOU MUST BE EXTREMELY CAREFUL!!!! With the engine running place the end of the screwdriver on the part you think is making the noise(waterpump, alternator, etc.) , put your ear up to the handle and the sound will be amplified. This should help you narrow down the possibilities. Remember USE EXTREME CAUTION!

 

think i found the idle issue. put the engine on the air compressor tonight to look for boost leaks... at about 10psi my Hallman MBC was leaking like crazy!!! researching it now. any ideas anyone?

 

^its not on backwards is it? lol

 

I think this is normal maybe its the injectors becuase injectors tick you know I think its perfectly fine. I though the ticking noise sounds like a slap. the idle issue is the computer compensating to have the car run a certain way through the temperature due to the maf sensor it controls the fuel and air ratio when it relays information back to the computer.

 

i can hear the injector ticking, and im used to it (this is my 4th 4G63 engine). but this sound is new. i didnt have time this weekend to look into it that much besides doing the boost leak check. but it does seem that the MBC leaking is normal, although i swore that i did a boost leak check right after i installed it, and it didnt do that... but oh well.
no vacuum leaks, besides a small on at the TB that has been there since i got it. going to change out the spark plugs tonight and see if that helps. the idle is getting realllllly bad now. sometimes is bounces from 1000-1200, and other times it dips down to 850 like its supposed to, and then starts sputtering and almost sounds like its missing on one cylinder. idle is choppy and exhaust is inconsistent.

we'll see if the new plugs help. if not, then im taking her to the dealer for further investigation.

 

update. change spark plugs, but no change.

uploaded a video with the current state of the car. if i cant figure something out by monday, im gonna have to take her in

this one is mine
http://www.youtube.com/watch?v=r9HQ-txHOtk

this is another i found that has a bit better sound and sounds JUST like mine.
http://www.youtube.com/watch?v=HBXZvYaA-Hs

does this too
http://www.youtube.com/watch?v=iuNeSmWauOU

 

current theories i am chasing down:

bad/dirty iac
dirty MAF
EGR
O2 sensor

im kinda lost on how to troubleshoot these things to see if they are the problem or not though. on the EGR, i've seen threads on how to completely remove it, but not how to check it.

 

could be intake vacuum leak, some where by the nipple

 

I just recently had a similar issue with my iac, but my car would barely hold idle before stalling out. Also had 3 vacum leaks. The 9's have a better design iac over the 8's and with you're low miles I'd doubt your's went bad, but they are easy to take out and inspect. they don't really get dirty, they break. If you're o2 was dirty/bad car would most likely be throwing a code by now.

 

the iac motor might be failing, maybe thats the rattle your hearing, honestlly though. your car sounds pretty healthy to me. sounds kind of like you have cams in your car already.

feel around behind the intake manifold and check the egr solenoid to see if any vaccum lines came off.

also maybe you can clean the egr to see if that helps. good luck.

 

quick update.

new plugs, no change
reverted to stock ECU image, no change
removed and cleaned the EGR, new gasket, no change...

GRRRRRRR!

takin her in this week. dammit

 

quick update...

took the car in today. tech was super cool and seemed very smart at his job.

explained that it wasn't the:

O2 sensor - cuz the O2 was responding correctly via their computer and computing fuel trims properly

IAC - cuz it can't regulate the idle that fast. oscillations we like at 1hz or less it seemed

probably was:
MAF
EGR

got a call later. it wasnt the EGR valve, which i had cleaned out. it was the EGR solenoid.
they could replace it for $300 (total, including diagnosis), or remove the EGR system and cap it off for $100 (total, including diagnosis).
told em to kill it. asked about the possibility of throwing codes, and the manager said that the tech advised that it most likely would not throw codes because the turbo engines are not as sensitive or something.
i've seen a few EGR eliminator threads talking about bridging pins with a resistor and stuff, so if it throws then i'll just go that route.
otherwise... she should be back tonight!!!!! woooot!

 

But did that do anything for the rattle? Because my 8 has been making a small metallic clinging like the video you posted, but only under moving acceleration and if the car is rattling from bumps. It sounds almost as if you put a tiny pebble in a metal pipe like the intake or the uicp (obviously thats not what it is). And I'm almost positive its coming from the engine.