Bottom knock from Y34 - engine is toast? [SOLVED - catalytic converters]

[Double E]

2004 Y34, 91K miles, religiously maintained with OCI at 3K miles (M1 Synthetic 5/30and Purolator Gold filter)
First I had a bad crankshaft sensor. P0340 appeared. Car would shut down after a short drive. Sensor replaced and all was good for one round trip to work (30 miles) total.
2 days later, upon startup, I have I have a metal-metal knock from the bottom rear of the engine. The knock is prominent at idle but when it revs, it is not very loud at all. The engine will not rev over 5K.
A stethoscope on that area indicates it’s the bottom rear of the block.
I pulled the sensor out to make sure it was not hitting something. It isn’t.
Today I took it to dealer for diagnosis and they say that it “could” be the cat converters are destroyed and blocking the exhaust, keeping it from going over 5K. They offered to replace just both cats for $4100 total.
Price aside, the problem is that new cats do nothing to solve the knock or determine what it is or how to fix the knock. The cats might not even be bad.
I have no CEL codes.

Suggestions?

[Ilya]

Any other ECU codes?

AND LOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOOL @ $4,100 for two catalytic converters. HOLY CRAP!

[lovemycarM35]

that's crazy are cats that expensive

[svard75]

Good choice on using a steth. It's not a good sign but start by draining your oil and watching it then use a magnet through the oil to see if there are metal shavings in there. I would also drop the oil pan to have a good look at what is in there. Metal shavings in the oil likely means a bottom end rebuild. What happens when you hit 5k and try to go higher? Does the engine shake while making the noise? What octane gas did you put inside? I'm also wondering if you've cleaned your injectors and checked the plugs because knock could be a result of a prior issue which caused the engine to detonate.

Regarding the cat. If you drive the car as it is now does it feel like it's hesitant and with less power than normal? It kinda feels like there should be much more but the engine is struggling?

[Double E]

At 5K there is more pedal to the floor but nothing happens. It doesn't shake or begin to stutter, it just does not continue to climb. It shifts through each gear fine. The knock is definitely not spark knock or valves.
It always gets 93 with a big bottle of Techron every 3000 miles. New plugs went in at 75000.

I like the suggestion of dropping the pan. I may try that.

To add insult to injury, I was quoted $18,000 for a new engine. (They must be thinking I'm in Colorado!)

[Six_Legs]

...I was quoted $18,000 for a new engine. (They must be thinking I'm in Colorado!)

...and from another planet!!!


Sooo ridiculous.

[EniGmA1987]

Sucks to hear about your problems
This might be compatible with your car: http://www.ebay.com/itm/03-04-INFINITI- ... 1172906738


It is possible that some error is causing the ECU to be in "safe mode" which is limiting you to 5K rpms.

[svard75]

Good idea but you would think that safe mode would be much lower rpms. Anyhow if its your daily driver buy a bike and start saving for a used motor.

[Double E]

Update:
I went to the dealership, had them put the car up in the air so I could hear exactly where the knock was coming from. It’s certainly the cats. Never thinking the cats had failed had me pointing the stethoscope at the block and I don’t have a lift at the house…
The mystery is why they all failed.
I’m going to have new ones installed (Calling IOS) today but I sure don’t want to put a new set on to have them fail again.

[EniGmA1987]

excessive unburned fuel leaving the combustion chamber could cause them to fail. If you have access to someone who has the Cipher program from UpRev you could look at a lot of very detailed things including seeing your A/F ratio. You may be running too rich which is causing fuel to burn inside the cats.

[Double E]

Ordered everything from IOS. Those guys are the best. Even after shipping across the US, I still saved nearly 1K.
Fingers crossed the fix is in those new cats.

[svard75]

Cat failure is typically caused by unburnt fuel igniting in the cat chamber. Now I am wondering why you didn't notice any Codes. Something like that should have triggered P0430.

[Double E]

Agreed... I should have received codes also for the gas pedal going to the floor and acceleration not happening.

The only thing I can think of is that I'm aware enough to noises such as that knock that when it began, the car was not in a ready state long enough to see the condition. Then, I didn't drive it beyond a couple of miles after and maybe it never went into the loop status to begin monitoring that stuff.

The knocking is significant enough also that maybe the cats are only partially cooked and it had not yet triggered the code or my rear O2 sensor is lazy.

I wonder if pending codes would have appeared? I never thought to look for them.

[EniGmA1987]

You can actually see all kinds of errors and the GPS coordinates they happened at, only some of the errors trip a service engine soon light, many errors do not as they are considered "minor". Perhaps as you said the car didnt run long enough or far enough to trip a major error code, but you may find a group of smaller codes in the memory.

[Double E]

In the memory ..with GPS coordinates......as extracted using the Cipher program?

[EniGmA1987]

You can turn off your audio, then press and hold settings down. Now turn the volume knob 20 turns. it will access a secret diagnostic menu (at least on the 06+ models). Now press and hold settings again, and turn the knob some more. It will unlock an even deeper diagnostic menu where you can see all sorts of hardware based stuff and error logs. it wont give you the full code readout, but will give you some of it at least on the in-car menu. Full code will require an ODBII scanner or Cipher program still.

[Double E]

Gotcha...that does not apply to the Y34. It's a different enough animal.

[svard75]

Go to any Autozone for a free reading. Funny enough I have a bad cat as well and code P0430 comes up but only after a few months of clearing it out. As a pending code it appears after a few drives.

[Double E]

Thanks for that. Got a code reader. Got a couple of them in fact.
I should mention that the car is currently sitting at the dealer, waiting on the parts to arrive at my house and I'll bring them over.
I have an extra car to drive in the interim. (2000 WJ 4.7L with 185K miles & '11 CTS-V)

[vexilix]

Does it sound like
[youtube]http://youtu.be/fIZXBDWokJ0[/youtube]
Gee i hope the link works.....

Most likely its your idler pulley.
Thought it was the fuel damper.

[vexilix]

http://youtu.be/fIZXBDWokJ0

[Double E]

Most definitely, the problem is not the idler pulley. It needs to be replaced on mine ...and I have that part on my workbench ready to go.

The issue is at the cats. I went to the dealership, had them put the car up in the air so I could hear exactly where the knock was coming from. It’s certainly the cats.
Parts arrived and were put on this week. I'm out of town but will be able get it back on Monday the 18th.

[Double E]

Update: New Exh. manifolds and main cats replaced. Runs like new.

The old cats were broken up inside...large pieces mostly in all 3. There's probably a few small pieces further down but I'm not worried about them.

Still wonder why it happened but glad it's fixed.

Idler Pulley replacement is next...

[MaxBolus]

Glad to hear a happy ending!