loud pitch sound coming from engine bay [SOLVED - intake gasket]

[cruzad3r]

folks

i'm running out of ideas so i'm hoping someone here knows or have an idea.

background - intake tube, plastic couplers were torn/ripped. drive the car for a while under this condition while i ordered replacement part. maybe too much air, the ECU was trying to compensate then one day, i can feel the car hesitated/almost stalled but didn't quite.

fast forward, one day came this loud a** pitch noise from the engine compartment. i know it's not belts related because all my belts are in good perfect conditions. i thought it was the MAF failing because I did get P0171 error code then came p0450 finally i have the p0300.

what i've done: replace the entire intake tube with new Berk system and couplers. replaced new OEM Nissan MAF. have B1S1 Bosch sensor on hand, but what really drives me nut is the god awful LOUD pitch.

so, do any of you kind folks have an idea or had this happened to your car? please advise,

[Ilya]

Might help some people here if there was a video or narrowed down to which part of the engine bay...have you tried one of those mechanics stethoscopes to narrow down the location?

[BlackCat81]

Any unrelated work done? Did you have the upper intake plenum off for any reason?

[cruzad3r]

i installed motordyne kit (the thicker one) with metal spacer by the throttle body at least 2-3 years ago and haven't had to touch it since. I did removed the throttle body several weeks ago to clean it and to install the new BERK metal intake tube.

so now the car is definitely misfiring bad. so i'm going to replace the spark plugs - for all I know, these are stock since i haven't replace the things since i bought the car which is years ago.

next is the O2 sensors - both upstream one. the worst part is the space is so limited, i think i have to get to it from underneath the car.

video of the nonsense - http://vid66.photobucket.com/albums/h24 ... 182055.mp4

[EdBwoy]

Cruzad3r, hold off on the spark plugs and o2 sensors!! Tune ups are good, but your issue might be in the intake. Might you have dropped the throttle body or impacted it against something when you removed it? You'll notice in the video that the sound is a little muffled when you touch the throttle body ~18 seconds in.

The black plastic can come loose off the aluminum body. Look for cracks on the edge of the plastic as well as missing/loose rivets (4 of them hold the plastic to the metal). Newer designs as well as rebuilt units usually use screws/bolts.

Or a simple test is just to grab the back of the throttle body and squeeze the plastic towards the front of the car. Sound should stop.

[cruzad3r]

are you referring to the gasket - throttle body gasket? when i took it out, i was very careful. the different between this and the last time i took it out was taking a little bit longer time/harder (maybe) to remove the plug electrical connection. i did not drop it nor touch the butterfly valve when cleaning.

the funny part now is the pitch seems to disappear when the car is under load. Also cold start the car in the morning yield absolutely nothing, no noise pitch other than engine was stumbling/misfiring. i'm going to see if i can smoke test this at the garage and will report back.

for other folks who have higher mileage car - do you remember any pitching noise when your MAF or O2 sensors were on their way out?

[EdBwoy]

Nope. The black plastic casing that the plug connects to the throttle body through. It has the servos that activate your throttle plate.

[cruzad3r]

oh you're talking about the throttle itself. man i hope the dam TB doesn't die on me because that part is mucho expensive.

stay tune folks -

[BlackCat81]

I've said it once, I'll say it a million times. NEVER EVER, EVER, clean an Infiniti throttle body.

[steve_c]

Good video!
My next step would be to take a mechanic's stethoscope (They are cheap, you could fab one yourself if need be) and try to track down the source of the noise. It sounds like a whistle. I would then use a CAT safe spray, or some oil to apply onto the area where the noise seems to emanate from. It sure does sound like it is vacuum/pressure related air issue! I would also be curious to see what vacuum you are getting at the plenum using a pressure/vacuum gauge hooked up at the nipple on the left front of the plenum.
A stethoscope with nice ear muffs or plugs works wonders in blocking out surrounding back round noise while honing in on the noises picked up at the probe.

http://www.amazon.com/Lisle-52500-Mecha ... tethoscope

[cruzad3r]

my suspicion started with vacuum leaked then electronic failure then now with everyone that i talked to keep saying it's a potential leak, i guess i'll go back to it. My goal was to take the whole friking top end out down to the intake manifold and see if there are any brittle vacuum hoses or busted gasket.

Steve - what would be a good pressure at the upper collector? better yet, what is a good overall vacuum pressure of a healthy VQDE35 engine? Thanks

[steve_c]

Yes, You can rip it all apart on the blind, but the stethoscope could possibly hone in on the exact area of concern.

I will hook up a gauge to my U/C & get back to you with readings ASAP.

[EdBwoy]

Use any suitable metal rod if you want a quick stethoscope or try to locate the $10 stethoscope from O'Reillys or the like.

Did you try applying pressure to the back side of your throttle body to see if it stopped? Inspected it?

You made an awesome video and that definitely sounds electronic to me. At least when my TB was on the fritz it sounded exactly like that. Used some channel locks to quieten it but eventually replaced it.

Good luck, and I hope whatever you find is not an expensive fix.

[steve_c]

This is a good diagnostic thread. A few causes possible, electronic noise/TB, or possible vacuum leak!
As EdBwoy says, any suitable rod can be used. Solid rods will pick up internal mechanical noises best. To be effective for vacuum, or pressure leaks (air whistles/noises, anything generating decibels), hollow tubes are best. All auto parts stores carry stethoscopes. The lisle one is a good tool.

Regardless, could be electronic TB issue, so best try to eliminate a vacuum leak since it is potentially easier with a few simple tools & checks.
These are the readings from my 2006 M35x, taken from U/C vacuum port a few minutes before this posting:

Notes:
Car operating temp about 140 to 160 (warm, not at full temp)
Car has 115k miles, upper & lower plenums were off recently & same gaskets were re-used on assembly. No noticeable problems or codes present. Plenums re-assembled using FSM torque settings & torque sequence.

Engine in Park @ 650 RPM = 21"
Engine in Park @ 2000 RPM = 22"
Engine in Drive @ 650 RPM = 19"

I am in the low end of the safe zone (about 18 to 25" is the zone). What are you getting? What is everybody else getting?

[cruzad3r]

are you simply using a pressure gauge at the upper collector nipple, right in front driver side? if so, what kind? Do you have the torque app with a BT OBDII dongle? Have you tried using it? PM me if you want to talk more about this app for android.

the top end have been off since yesterday. i'll post what i think is the culprit. i went to an indy mechanic and he spray brake cleaner around the loud pitching area and he called it. it's a frikin busted gasket by the intake manifold. will post picture soon.

i also tried to switch out my passenger's side (bank 1) upstream Oxy. That son of a gun was painful. i tried everything, took the bottom metal brace off to get more room but the dam drive shaft is in the way. the top is way to busy with crap. couldn't do it so i give up.the manual said you have to take the CAT out and I do not want to mess with it simply because I do not have time or the tools to cut off rusted screws. i changed all my plugs. used ngk PLFRA5-11 gapped at .043. with the top end out of the way, it's easier for me to do these maintenance. i still hate the frikin wire loom. dam tight as hell.

so i was able to get to the driver's side (bank 2) upstream Oxy. with the bottom metal brace off, you can get in with a 7/8 wrench from the bottom. you can undo it with little force as it's only torque to 37 ft/lbs per manual. the valve cover and gasket on this side has gone to hell. there was a pool of oil in all cylinder. i don't have the parts and do not want to spend any more time on the car so i'll leave it as it. maybe next year.

tomorrow i will put everything back together and hope this whistling noise goes away. pray for me

one last favor, i took off a lot of these 10mm screws that are holding down the wire loom and i can't remember some of them. can someone please take some up close pictures of your engine and post or send me. thank you.

i will post pictures once everything is button up for future reference.oh and i do have the scope. i didn't use it because i was gunbound on tearing the top end off

[steve_c]

The nipple is on the front, as you face the engine, it is towards the passenger side. You can use any vacuum gauge measuring 0 to 30" Hg. By torque, I meant the plenum bolts torque using an inch pound torque wrench, not the blue tooth OBDII dongle...which by the way I looked up on U Tube....nice setup!

[cruzad3r]

ladies and gents - behold the culprit



one more for luck



everything is button up, drove it for about 15 miles - maybe 20 minutes and no loud a** annoying whistle yet. knock on wood this is it. also ran the test on the car through Torque, everything came back complete and pass. like i said, i swapped out all spark plugs and the bank 2 upstream Oxy which is post cat. Whoever could do the bank 1 upstream without taking the cat out is my hero because i couldn't touch it.

will post some more pic later. it's time for me to relax and spend time with my family. frikin 3 days (half day) on this car during the winter time outside is not something I'm looking forward to again. Thanks GOD it's 60 degree without any wind; otherwise I would die.

Folks - take note: if you're hearing any whistle/pitch or noise in general, spray some brake cleaner to the "trouble" area and if the noise goes away, you have a vacuum leak.

[EdBwoy]

ladies and gents - behold the culprit



.

So the issue was the paint layer peeling off the metal gasket or was the metal broken as well?
Glad you got it running well within a short-ish time.

[cruzad3r]

The problem as you can see from the picture is the gasket was broken at the lower collector to the intake manifold. That caused a vacuum leak hence the whistle.

[EdBwoy]

Ahh, I see now. Had to switch from the phone to computer to see the damage more clearly.
And I watched the video again, this time with surround sound instead of the phone + headphones (because we take this stuff seriously). Could hear a very slight hiss, but with the prevailing high pitch the outcome was quite interesting to me.

Thanks for sharing, will definitely save this in my troubleshooting guide.

[steve_c]

.....Folks - take note: if you're hearing any whistle/pitch or noise in general, spray some brake cleaner to the "trouble" area and if the noise goes away, you have a vacuum leak.

Yes, if Brake clean is CAT safe, it works! I make sure to use a CAT safe spray (I like carb & choke cleaner) as not to cause damage! Oil works well also (it blocks the leak, you feel the difference & see it on VAC gauge)

A whistling vac leak is rare. The broken gasket acted like a reed to produce the whistle. In many instances, you could hear nothing, or maybe a suction noise if the leak is aggressive. That is why I like to use a vac gauge & stethoscope to hone in on the leak. Once you find it, give it a bit of spray & oil, & watch the gauge!

For me, the video giveaway was how the whistle stopped under aggressive throttle, then resumed when throttle released. It mimicked what you would see if you were watching a vac gauge hooked up to the plenum nipple.! The other clue was the random misfire code, the diagnosis tells you to check for vac leaks on that one. Interesting, in the photo you can see the gasket was ruptured between cyl 5&6, causing the misfire of both, thus the random misfire code. Good stuff!

[steve_c]

My next step would be to take a mechanic's stethoscope....and try to track down the source of the noise. It sounds like a whistle. I would then use a CAT safe spray, or some oil to apply onto the area where the noise seems to emanate from. It sure does sound like it is vacuum/pressure related air issue! I would also be curious to see what vacuum you are getting at the plenum using a pressure/vacuum gauge hooked up at the nipple on the left front of the plenum.
A stethoscope with nice ear muffs or plugs works wonders in blocking out surrounding back round noise while honing in on the noises picked up at the probe.

Not to beat a dead horse, but I am curious what others are getting for a vac reading at the plenum!

Mine are:
Engine in Park @ 650 RPM = 21"
Engine in Park @ 2000 RPM = 22"
Engine in Drive @ 650 RPM = 19"

I am in the low end of the safe zone (about 18 to 25" is the zone). What are you getting? What is everybody else getting?

[cruzad3r]

i would agreed with everything that you said up until recently where the car was not whistling while under load. Meaning when idling, car would whine like a mofo but as soon as i accelerate, the whine stop until I let go of the gas. nevertheless, this has been a journey for me.

One more thing - these bolts on the upper and lower connector are very brittle. AS in it will break on you so do not use any torque or any 3/8 socket on it. use the 1/4 and hand tight. further, before you put the gasket on, lube it with a little oil so it will seal once you set it down and tighten it up.

i think i still have some vacuum and boost gauge around. i will fab one up and hook it to the upper collector and compare it to the Torque App which is showing around 25-26 HG. Right now my idling is back to normal, around 650 RPM and no more surging, stalling, or gasping for air. My wife drove the car yesterday and she goes, wow car is back to normal, instance power without any delay or hesitation.

[steve_c]

i would agreed with everything that you said up until recently where the car was not whistling while under load. Meaning when idling, car would whine like a mofo but as soon as i accelerate, the whine stop until I let go of the gas.

Yes! That was my biggest clue!
You heard the whistle because the break in the gasket was created in such a way that the gasket produced the whistle (rare)!
When full vac was present in the plenum, (throttle closed), the whistle was produced by the broken gasket similar to drawing (sucking in) on a harmonica to play a note.

Do not forget, at WOT (Wide Open Throttle) your vacuum drops like a rock (goes to atmospheric pressure)! Hook up a vac gauge & you can see it. That is why the whistling stopped under heavy accel., (no more vacuum in the plenum). The video clearly revealed this!

In the old days, many car accessories worked off of manifold vacuum. (A giveaway to my age) To prevent loosing vacuum to these accessories under WOT, one way check valves were installed at the reservoirs (vac. source feed side) so that when the engine was operating under low vac conditions (aggressive & WOT) the reservoir vac. would not be lost to atmospheric pressure, which would have rendered the accessory inoperative. The check valve kept the vac. in the reservoir to operate the accessory while the engine was under throttle condition!

Your torque app should see this, if it is capable of rendering real time engine vac. readings. I am not clear on how this app could see real time vacuum. How does it read engine vac without the aid of a transducer?

[cruzad3r]

The reading comes directly from ecu thru the obd2 connection. Granted it's slow as the baud rate is somewhat crappy. If i decide to keep this car longer, i have to buy the cipher uprev cable. I used similar tool cable on my audi to do all type of diagnostic and modding.

There was another Steve from the Audi forums that was very knowledgeable and maybe you are the Steve for Infiniti. Looking forward to learn more from you sir. We need more of that on this forum.

Jake