Potential probelm identified: Post #24

I’m cursed

I've developed a noise and a boosting issue: I can't nail down if it's a rod bearing, bad lifter, facked turbo, exhaust leak, loose bolt, etc. The noise doesn’t bother me as much as the fact I’ve lost boost and the car is asthmatic - here's the deal:

Turbo was boosting well to 15 psi without breaking a sweat for the past 3,000 mi. until last Thursday, where it would only boost to 11 psi, then a little later only 10psi (at which point the open dump didn’t open), then only 9psi, then 8, etc. etc. Max boost I can now squeeze out of it is 6psi.

It's breaking up in the upper RPMS and the AFR bottoms out when I do squeeze the boost (9.3 – 10.0 as soon as I’m no longer under vacuum). The turbo *sounds* like it’s spooling fine, but just taking forever to get much out of it. It behaves as though it’s boosting fine and the MAF is responding to the increase in air, but the air isn’t making it to the plenum. However (as described below), all connections are 100%.

Here's the heartbreaker: Makes a sharp rattle noise somewhere between 2k to 5k rpms, depending on what gear and how you feather the pedal. It almost sounds like a heat shield rattle (or gasket); it's a high-pitched 'tinny' sound, not a deep knock, and I can't keep a steady RPM to hear the noise - you have to accelerate ever-so-slightly to maintain the noise, and what you can hear at 2500rpm in 2nd gear you can't hear until 3500rpm in 4th, etc.

When I listen to videos showing rod/bearing noise, it’s nothing similar; and the range in which the noise can be heard and position of the throttle is so narrow. I cannot emulate the noise while free-revving in motion or in idle. I’ve crawled around under the car; no noise to be heard.

It idles perfectly fine (no noise, 14.7 afr, etc.); mild acceleration and cruising are perfect... revving motor in driveway to 7k rpms - sounds perfect. Push in the clutch while cruising - butter - no issue.

Oil pressure is fine: 90 psi on startup, mid 60's when cruising, 35 - 40 when idling; responds to throttle input. Oil level is right where it needs to be.

Temperature is normal. EGTs are normal. Vacuum is normal (-15 to -17'ish).

Cipher hasn't revealed any obvious issues; have yet to bring up UTEC and log anything (i.e. knock). I do own a CONSULT-II but haven’t plugged it in, and don’t think that’s going to reveal anything else at the moment. I also have not tried changing to a different MAP, still running on the 91 octane MAP.

The only CEL is the standard P0300 (random misfire) - comes and goes and has been that way since I installed UTEC a couple years ago.

I spent hours under the car today - can't find a loose bolt or clamp; nothing rubbing anywhere. Sucked up a little Seafoam through the intake today – nothing but smoke out the exhaust; no leaks found in the engine compartment. Connections from the turbo to the intercooler and up through to the throttle body are tight.

I’m stumped, and looking for ideas/suggestions on what to pick apart next. The only things I can focus on at the moment are dropping the oil pan and turbo and visually check for damage? Any other suggestions to point me in the right direction would be appreciated.

Motor details:
3,500 mi.; built block (Eagle rods, Arias pistons, GTM cams, HKS hg, L19 studs, VQ40 water upgrade, JWT springs, RC550 injectors, std. fuel delivery, turbo changed to GT3567R, Tial WG with open dump (approx.. same amount of mileage).

 

I hate to say this but sounds to me like maybe one of your piston heads is letting go and the tinkling sound is the debrise rattling around. I do hope I'm wrong .... I have 3 destroyed pistons in my office at work from exactly these symptoms.

At the time I thought it was pieces of my cat rattling around inside the converter but turns out I was wrong ....

Edit: re-read everything and it sounds like detonation but the about happened to me with similar sounding noises ....

 

I've ruled out detonation; sound is not the same as previous detonation issues, and all sensors/wideband are picking up a *very* rich condition.

Can't imagine it's the piston breaking apart; such a narrow band of throttle/rpms and only during acceleration. No symptoms otherwise (smoking, etc.)

I can't positively correlate the new sound with the lack of boost/rich condition; assuming they are interrelated at this moment.

 

Maybe a leak!! They can be very noisy.(ticking sounds)

 

sounds like a turbo issue....dont quote me on that though because im no advanced turbo/engine mechanic but i came from a family of turbo'd mazdas (mazdaspeed community) before i got my 350z...and thats just what it sounds like based on the symptoms.

 

you can ping from being too rich as well....

did you drop your oil pan and check for metal?

 

How's the air filter looking?

 

Sounds like a boost leak, it doesn't mean a boost leak will be a vacuum leak......so at idle things may appear OK but the leak may only open under boost.
Double check everything related to vacuum/boost: piping,lines,controller etc....you''ll be surprised at were leaks can show up.

It will help a lot if you can get your car on a dyno.

 

Does it do it when you rev in neutral or only when motor is under load?

Tom

 

Haven't dropped the pan yet; that's on the to-do list.

Pressure tested the system last night; as suspected: no leaks at any point from the turbo to the manifold

Air filter looks acceptable; no holes or debris.

Only makes the noise when under load; I can't maintain the sound at a specific speed/RPM, based upon position of the throttle I'm always accelerating a small amount to keep producing the noise.

Driveability when not in boost is fine; although it still makes the noise in that specific throttle/RPM range

 

get us a vid......but thats not a good sign

 

that sounds alot like detonation. you need to log that UTEC and check for knock. The loss in boost without a leak is also very worrying.

 

Put in some octane booster to rule it out. Maybe this is all due to a bad tank of gas and your EMS trying to save you (FCON?).

If that checks out, I'd open the coupler before the IC and see if there's anything from the turbo sitting there. How easy is it to look at the turbo on your kit?

 

Are you running an internal or external wastegate? If external I'd pull it off and look inside.

 

Using UTEC as my EMS. Looking at the Cipher logs, didn't see anywhere that timing was retarded in relation to when the noise occurs. In fact, none of the items monitored were observed to be out of range or respond to the noise. There's a local station that serves up 101 octane - I'll throw a couple gallons in there to rule out detonation issues.

I checked the intercooler; no oil, no spare parts. I run an APS ST so dropping it will be somewhat involved but not impossible, and at this point necessary.

I have an external WG; will remove at the same time - I would think, however, if it were stuck open and bleeding out boost that I would hear it through the open dump?

Anything else I should check off on my list? FPR perhaps? Change to a different MAP on the UTEC and retry?

 

I've seen the pins break at the base inside the wastegate and depending on how it's sitting make some pretty rediculous noises rattling and semisealing it at the same time.

Other than that you've got a good list.

 

Added 101 octane on an otherwise emtpy tank; problem unresolved after 40 miles.

Logged UTEC; no knock detected on any of the 3 maps at any point in the RPM spectrum (which I feel is good sign).

All 3 maps tested; all three result in the same noise, same lack of power and same rich condition once in boost.

At this point, seems all I can do is drop the turbo and poke around unless anyone has other suggestions for me to try?

 

Fouled plugs??

 

I started losing boost when a tear developed in the rubber flex pipe the APS ST kit comes with. I had a small piece of it get pulled into the turbo, but it didn't harm it and that doesn't explain the ticking noise in your case.

 

He did a pressure test. I guess turbo would be my next on my list also.