Clack clack diag

[blackobxt]

Alright guys, now that weather is cooled down into the 40’s the 05 obxt has started having some cold start noise. When you first start it it has some clattering noise that sounds like rod knock or piston slap that goes away once warm and until it’s fully warm, in neutral if you hold it at 2k rpm you can reproduce it but it’s at exactly 2k only.

 

The motor has less than 20k on it and has since day one always had an odd slight miss between 2k - 3k that I always thought was avcs related. When I did the short block, I had the avcs gears gone through and Instead of replacing the solenoids, I actuated them with 12v and cleaned them out really thoroughly.

 

The question is has anyone dealt with this before? Would a screwy avcs show up on opensource data?

[xt2005bonbon]

You should be able to log the avcs angles L and R. They should be in sync under load. If one is stuck, then the numbers would show it.

 

I don't recall people reporting knocking noise when the avcs were failing though. Mostly, running rough and poor performance.

[Infosecdad]

Sounds like it might be piston slap.

 

Is the rebuild all OEM or are there some aftermarket parts in the internals?

[blackobxt]

I was also thinking piston slap. All parts are oem internally, shortblock was new oem.

[xt2005bonbon]

mmh. I installed a type RA block back in May. I do not experience piston slap, or at least I can't hear it at all. Which oil are you using?

[rhino6303]

Injector noise since cold start has high idle?

 

The sewing machine sound can be quite loud.

[blackobxt]

Rotella 5w-40 fresh about 1,000 miles ago. Of all the short blocks I’ve done in these, this would be the first I’ve done that developed piston slap. I’ve serviced high mileage turbo ej’s that slapped away, but with less than 20k, doesn’t burn a drop of oil, and this motor has never seen more than 5k rpm, never more than 9psi and never been in positive manifold pressure for maybe 2-3seconds. It’s been treated like a caged lion.

 

The only thing I could think of that could be making the noise could be an avcs gear possibly clattering away. It could be piston slap, it would just surprise me

[xt2005bonbon]

Then log the avcs angles asap and report. I am curious now.

[rhino6303]

Timing belt tensioner? Those are notorious for failing and clacking away.

[xt2005bonbon]

True. I had one fail in the middle of nowhere while moving and pulling a trailer. Perfect timing.... Somehow, it did not bend the valves even though the timing belt was no longer under tension.

[blackobxt]

I’ll figure out logging and post results. I’ll probably have to wait until it cools off tonight to get any results with the noise. I started it just now for the first time today at 65° and it was quiet as ever.

[blackobxt]

Well a not so update update. I have yet to reproduce the noise and I know what a lot of you are thinking, heat shield or injector clatter. I can promise you that if it was, it’s unlike any I’ve ever heard ever on any vehicle at all! Closest thing I can associate the sound and symptoms of would be the Vg30de or vg30dett when the springs wear out for the variable valve timing and Toyota engines when their variable valve timing goes awry.

 

I still have the rough running from 2k ish to 3k ish rpm that’s always been there that I’m now motivated enough to find the culprit of but I’m half tempted to tear this thing apart just to figure out wtf was making that noise

[Max Capacity]

between 2 and 3000rpm, is that the surging your feeling or a miss fire?

 

These cars are known for a surging fell from 2400-300rpm.

 

Most of us have fixed that by connecting the vacuum line from #4 intake runner to a T we install in the line off the blow off valve.

 

[xt2005bonbon]

I’m half tempted to tear this thing apart just to figure out wtf was making that noise

 

 

Before you do that, log the VVT (AVCS) angles. Also log per cylinder misfire.

[xt2005bonbon]

between 2 and 3000rpm, is that the surging your feeling or a miss fire?

 

These cars are known for a surging fell from 2400-300rpm.

 

Most of us have fixed that by connecting the vacuum line from #4 intake runner to a T we install in the line off the blow off valve.

 

[ATTACH]288117[/ATTACH]

 

 

I need to try that. Still have not done it.

 

Looks like your line in your pic is not plugged on the other end no? Should be plugged to the fuel thingy (can't remember how it's called )

[blackobxt]

between 2 and 3000rpm, is that the surging your feeling or a miss fire?

 

These cars are known for a surging fell from 2400-300rpm.

 

Most of us have fixed that by connecting the vacuum line from #4 intake runner to a T we install in the line off the blow off valve.

 

[ATTACH]288117[/ATTACH]

 

That’s exactly what I’m experiencing and will be trying this tonight

 

 

As far as logging and diagnosing before I tear it apart, I will definitely be doing that. I spoke more out of frustration than anything, last thing I’d do is create unnecessary and potentially fruitless labor. It’s obviously nothing currently catastrophic, bearing knock doesn’t just come and go

[xt2005bonbon]

Don't forget to rule out the tensioner just in case. Did you put a brand new OEM unit?

[blackobxt]

I did, and about 4,000 miles ago I pulled the drivers timing cover to check everything and all is well. But I will check again, preferably when the temp is cold to verify the hydraulic tensioner is doing it’s thing even when cold

[Max Capacity]

That’s exactly what I’m experiencing and will be trying this tonight

 

 

As far as logging and diagnosing before I tear it apart, I will definitely be doing that. I spoke more out of frustration than anything, last thing I’d do is create unnecessary and potentially fruitless labor. It’s obviously nothing currently catastrophic, bearing knock doesn’t just come and go

 

Remember to reset the ECU after making the mod.

[Max Capacity]

I need to try that. Still have not done it.

 

Looks like your line in your pic is not plugged on the other end no? Should be plugged to the fuel thingy (can't remember how it's called )

 

All hoses are attached and the nipple in the runner is plugged.

 

The hose that went to #4 runner is still attached to where it came from. I just moved it to the BOV "T" that I added.

 

And also reset the ECU.

[blackobxt]

Update: I had some unfortunate luck with the Subaru, I was out with the family and the radiator end cap on the top just flat out exploded. Luckily we were close to my in-laws and I was able to limp it there without it getting hot. While it was there I decided to do a boost leak test and found several leaks including the intercooler, the throttle body hose, the brake booster hose where it connects to the booster and a few small leaks that didn’t show up till I got 7psi in the intake. It was with Christmas and several other unfortunate costly expenses that I needed to make some budget minded parts purchases that I’m fully prepared to be flamed for. I ordered a good radiator (won’t cheap out on that) an avo throttle body hose and an eBay rev9 intercooler (I already have my burn cream so flame away!). The radiator went in in like 10min, the rev9 however required all the work everyone talks about including one I hadn’t heard about yet. The intercooler hit the bracket above the pitch mount that holds the ac hose in place. I don’t know if this is because i still have the spacers and the engine sits lower or that my motor mounts are old and it’s sagging a bit but some slight bending of the bracket made it clear. I did everything in my power to make the intercooler fit straight and I’m happy with the result.

 

I did re-rout the line max pointed out and sure enough the car no longer has any clack clack at all and running smoothed out a lot. It still has a slight stumble right at around 2,100rpm but is considerably less. I suspect the intercooler has been leaking since I put the car together but now that it’s replaced, I’m seriously considering doing a pump and injectors so I can actually take advantage of the bnr 16g. Also since the cars been down, I’ve been driving our low mile tight suspension 7.3 f350 which really made the flaws in the bushings and mounts on the outback stick out painfully. I wont be able to overlook these anymore so it’ll be time to make the old girl feel nice and tight again, just need to see if I can get everything together to ditch the subframe spacers before I plan that project.

[JJr]

Off topic a bit but you mentioned it so... how many miles on the 7.3? Those babies are worth a ton out west!

[blackobxt]

03 7.3 4x4 lariat crew cab short box 104,000 miles. Low to me anyways

[Max Capacity]

Before the pump and injectors, run a couple can's of Chemtrol Beeryman B12 fuel system cleaner. https://www.walmart.com/ip/B-12-Chemtool-Fuel-Injector-Cleaner/16817404?wmlspartner=wlpa&selectedSellerId=14&&adid=22222222227016736244&wl0=&wl1=g&wl2=c&wl3=79429703448&wl4=pla-110348932848&wl5=9003193&wl6=&wl7=&wl8=&wl9=pla&wl10=8175035&wl11=online&wl12=16817404&veh=sem&gclid=Cj0KCQiAzsz-BRCCARIsANotFgMiUmpe4_HiNONyLYD1rHvAi6dfWgutNtNp1WnfFA1u6QB31ymlKqsaAoRnEALw_wcB

 

I do one can in Fall. Just because...

[blackobxt]

When I was building the motor I actually back flowed the injectors and got little chunks out of them. I’ll still flow a can of that stuff through just to see what happens. I’m looking at injectors and most of them say 04-06 sti and 05-06 lgt but list obxt as not compatible. Aren’t they the same injector between lgt and obxt?