FromGtoZ

Hey,

So I was looking for ideas as to what could be causing my issue. I'll go through the symptoms and what I've done to fix it.

Owned the car since 08, has been my daily driver, 140k miles |2003|6mt|Agency Power Single|replacement DE engine (I put 15k miles on it, it had 50k, total 65k now, 1 year in car)|(very dirty) K&N drop in filter|(most recent possibly significant event was royal purple oil/fram wrench on filter change 2500 miles before)

Issue started suddenly:


-I turned an uphill corner while downshifting and noticed a different exhaust note (Agency Power Single) than it had literally just been making and it had always made.
(I rev match, I'm not too rough on the car)

-I got out and revved it to listen from outside to confirm. Definitely muted (usually horrible drone and annoying.. you know when it's different) AND a weird subtle extremely hard to describe noise (I try to describe it at bottom) from engine, that I can hear inside when I am driving or revving to higher RPMs (~3700+)

-Thought it was weird so I took it to a back street and realized it is down power as well, however the loss is linear, it feels exactly like how it used to feel, but it is just maybe ~20% less powerful. Like it pulls in the same RPM range it used to, just not as hard, and it lags in the same RPM range, just more.

Steps I took took to fix it:

-Inspected plugs, found a little oil in 6, and still a little but more in 5. Everything else looked ok so I just replaced those. No change.

-Pulled the clip on each cylinder when it was running to see if one was down (because this is what I first thought it was) None made a difference.

-Got the codes checked, only had the knock sensor code. Thought this was it for sure(symptoms made sense), got the new sensor AND harness, replaced it, as well as added motordyne spacer. Negligibly more powerful, but not normal still. Reacted like a functioning car would, but its just like the curve has been moved down. Slightly deeper note, but not the normal note, just a deeper version of this weird one.

-Cleaned MAF, put in clean paper drop in air filter, cleaned TB, did every reset, TB open/close, idle air learning, and complete ECU, like 6 times. Nothing

Now I am completely lost. Drove 50 miles yesterday, not a single code.

In short:

*No CEL/no code
*All throughout RPMs while moving and free revving, weird noise from engine, slightly reduced power and strength in exhaust note
****The only time it ever sounded/acted close normal was this morning for 30 seconds maximum when the car was completely 100% cold and 10 seconds after took apart the plenum etc to get to knock sensor and reassembled. This morning I got out of my driveway and went WOT to see if it was normal and it seemed normal for a second and then back to reduced power.

The closest thing I can say to describe the noise is like a subtle deep whizzing or vibrating. It sounds like the noise when you take a plastic wheel of a toy or something and spin it really hard by hand.. I think they use this sound effect for like UFOs in movies to simulate something speeding and whizzing by your head. My old motor had cylinders die one by one until it sounded like an STI(legit people thought it was a boxer motor) so I know what that noise it. It's new for sure, and it isn't that.

Sorry if this was a long post, I just don't know what to do, the no codes and hard to describe noise makes it super hard to search, but I have tried, for weeks.

GreyZ

iTrader: (2)

Blew your Catalytic converter Im nearly positive. one or maybe both are now clogged/partially clogged.

FromGtoZ

Wow, thanks for the quick reply!! There is no smoke or smell, can this still be the issue? (not second guessing you, just adding more info, not sure if it makes a difference)

GreyZ

iTrader: (2)

Yup, the cats are still functioning, so they won't smell, but they are probably clogging the exhaust flow. Its much harder for the motor to rev. The catalytic material will expand when it heats up if it is not constrained in the canister like they used to be. This would explain the rattle/rough noise, and this would also account how it may sound normal right at first crank, but as soon as some fuel and heat hits the cats they heat up and choke the flow.

Edit: Grammatical Shitshow

FromGtoZ

Thank you so much @GreyZ . I'll try and fix it tomorrow night and post in here if that solves it, which hopefully it does. Thanks.

travlee

iTrader: (8)

not implying anything by the site, but some good info here

http://www.dummies.com/how-to/conten...onverters.html

FromGtoZ

Thanks. It says that if it gets clogged enough there is a pressure build up.. can that be causing my oil pressure gauge to be reading super high? Mine was never accurate but now it seems pinned to the max. Because this is relatively recent that this started, I know it was after the noise started.

GreyZ

iTrader: (2)

It could possibly, If your are having a ton of ring blowby and pressurizing your oiling system, but it doesn't seem likely. If removing the cats did fix this and the other issue, then your rings may possibly be shot. That's a pretty unlikely scenario though in my opinion.

Bigsyke

The sound you describe could point to the alternator.

I'd try checking your grounds. I noticed none of my factory grounds were contacting bare metal. It's like Nissan assumed the contact through the bolt threads would be enough.

FromGtoZ

I got lucky and it was just the cats, one was completely destroyed inside, I'm not sure how. Thanks for everything! I got to upgrade to ART Pipes which are great and fixed the issue completely, so it ended up being a good thing! Thank you everyone.

GreyZ

iTrader: (2)

Awesome, Glad it was something easy. ART pipes make everything better.