2005 Trailblazer knocking and running rough

[salth2o]

I'm new to the forum, but have used MAY03LT's youtube videos for a while to help with several fixes.

My Blazer has a 4.2L v6 w/ 154,500 miles. Two days ago it stalled as I was backing out of a parking space, then it started doing what I listed in the title. Within the last few months I have cleaned the throttle body, changed spark plugs (AC Delco's), and I just changed the oil last week.

I put some gas treatment in just to confirm it wasn't water in my gas. Below is a video of the knocking. It seems louder near the driver side door.

http://youtu.be/Do265NCiNhY

Any help or insight is greatly appreciated.

 

[808_LS_EXT]

You need to change the privacy setting on your youtube video in order for us to view it.

Select "unlisted" to limit its access...
or public for unlimited.

 

[salth2o]

Done. Sorry about that.

 

[808_LS_EXT]

oh crap!
that is a hellacious knock!

Sounds like a rod bearing...
but, being that it is accompanied by "rough running",
I'm also guessing it might be a broken rocker arm or dropped valve.

 

[808_LS_EXT]

Don't drive it or run it anymore until you pull the rocker-arm cover...
you may be able prevent catastrophic damage if you found/fixed a valvetrain problem sooner than later.

 

[salth2o]

I had a local mechanic and O'Reilly's run a scan. The only code showing up is P0014 - B" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1).

I apologize in advance for my novice knowledge of vehicles, but at 42 years old I have finally figured out how rewarding DIY can be, so I am learning. Is this code related to a rocker arm or valve issue? Would a different code show up for this or would it not show a code at all?

 

[gmcman]

Ouch....sounds like a double knock and since you stated it's running rough...maybe it could be a valve but sure sounds like a spun bearing. Would be great of it was the torque converter bolt(s) but not likely, however a very distant possibility.

I would drain some oil and look for metal. Also pull the plugs and look for carnage on the top of the piston.

If you have a vacuum gauge you can hook it up to the forward facing port on the TB and see if the needle fluctuates, if so then it points to an intake valve.

 

[808_LS_EXT]

I had a local mechanic and O'Reilly's run a scan. The only code showing up is P0014 - B" Camshaft Position - Timing Over-Advanced or System Performance (Bank 1).

I apologize in advance for my novice knowledge of vehicles, but at 42 years old I have finally figured out how rewarding DIY can be, so I am learning. Is this code related to a rocker arm or valve issue? Would a different code show up for this or would it not show a code at all?

waitaminute!!

Knocking, Misfire & P0014?!

Could it be your timing chain jumped,
and now your valves are hitting pistons?

 

[gmcman]

You should definitely see evidence of that through the spark plug hole...I'm very curious.

 

[808_LS_EXT]

Would justify the purchase of...

 

[Mooseman]

I just finished a timing chain job on mine and before the chain would jump, it would have been making an irregular clacking noise on the top front of the engine. My chain tensioner went and that's what it was doing but the chain didn't jump. It wasn't gone completely, it just wouldn't hold the tighter tension pushed by the oil pressure. Anyway, our engines are a close tolerance and if the chain was to jump, it wouldn't run or run extremely poorly.

It sounds like a rod knock.

 

[salth2o]

Here is a video of the noise from the engine perspective.

http://youtu.be/hzuv_M5g9j0


From the replies this sounds catastrophic or at least something that is beyond my limited skills and abilities to complete a driveway repair.

Thoughts on next steps?

 

[808_LS_EXT]

I just finished a timing chain job on mine and before the chain would jump, it would have been making an irregular clacking noise on the top front of the engine. My chain tensioner went and that's what it was doing but the chain didn't jump. It wasn't gone completely, it just wouldn't hold the tighter tension pushed by the oil pressure. Anyway, our engines are a close tolerance and if the chain was to jump, it wouldn't run or run extremely poorly.

It sounds like a rod knock.

Here is a video of the noise from the engine perspective.

http://youtu.be/hzuv_M5g9j0


From the replies this sounds catastrophic or at least something that is beyond my limited skills and abilities to complete a driveway repair.

Thoughts on next steps?

IMHO, it sounds too rapid to be a rod-knock.
By the way, what's the oil pressure gauge reading at idle?

The "easiest" next step would be to pull the plugs and inspect the tops of the pistons.
If the pistons are clean, then look deeper.
Sometimes, disabling the spark one cylinder at a time will help find a rod knock...
No combustion = less pressure on the rod = less noise from burnt/spun rod bearing.

 

[Harpo]

I agree it's to rapid for a rodknock, it sounds exactly as when my flexplate cracked on my Chrysler T&C. We can hope that's your problem. Never heard of anyone having problem with that on our platform though.
Good luck!

 

[Mooseman]

Don't bother with the dash oil pressure gauge. It's fake. The reading is fabricated by the PCM.

 

[gmcman]

Thoughts on next steps?

There's been a few good suggestions, what I would do first is remove the access cover in the front of the transmission and look for loose or missing converter bolts or a cracked flexplate.

Drain some oil and look for some metal shavings.

Pull one coil electrical lead at a time and see if the noise goes away or has a drastic change in intensity.

Report your findings.

 

[salth2o]

There's been a few good suggestions, what I would do first is remove the access cover in the front of the transmission and look for loose or missing converter bolts or a cracked flexplate.

Drain some oil and look for some metal shavings.

Pull one coil electrical lead at a time and see if the noise goes away or has a drastic change in intensity.

Report your findings.

Will do. I really appreciate the input and advice.

 

[808_LS_EXT]

Don't bother with the dash oil pressure gauge. It's fake. The reading is fabricated by the PCM.

^^^ Truth.

Mine (with bad stepper motor) reads like 180psi all the time... lol

However, I'm sure salth20 knows where his normal operating pressure is on the gauge (if it is functioning) ... if that norm has changed (lowered), then that would indicate a loss of pressure caused by a bad bearing.

 

[Sparky]

^^^ Truth.

Mine (with bad stepper motor) reads like 180psi all the time... lol

However, I'm sure salth20 knows where his normal operating pressure is on the gauge (if it is functioning) ... if that norm has changed (lowered), then that would indicate a loss of pressure caused by a bad bearing.

The problem is the gauge doesn't ever get an actual reading. These engines don't have an oil pressure sensor, just a switch. As long as oil PSI is at least 18 (or thereabouts I think) the gauge will read around 40. So he could drop 20 pounds and the gauge would still read the same.

 

[808_LS_EXT]

The problem is the gauge doesn't ever get an actual reading. These engines don't have an oil pressure sensor, just a switch. As long as oil PSI is at least 18 (or thereabouts I think) the gauge will read around 40. So he could drop 20 pounds and the gauge would still read the same.

I guess I'll have to invest in a REAL gauge, rather than repair the OEM.

 

[Sparky]

I still don't fully understand why they went through the trouble of programming the software in the computer to fake the whole thing vs just put a darn normal sensor in and output that to the gauge instead of dummy numbers.

 

[The_Roadie]

Switches are cheaper than a sensor and an analog measurement channel in the pcm to read it. They must had the measurement channel to spare in the V8 pcm.