2000 Monte Carlo SS 3.8L (no modifications)

Hi, I'm new here. Registering on a forum just to ask a question is definitely a last resort for me, so that's a good indication of how baffled and hopeless I'm feeling right now.

After several weeks of hot engine no-starts and occasional stalling, my engine finally refused to start at all. I had suspected the Crankshaft Position Sensor (CKP) all along, so I decided to replace it.

With the repair complete and everything reassembled/reconnected, I attempted to start the engine. There was immediately (less than 1 second of cranking) a loud noise and smoke pouring from the engine compartment. Upon inspection, I discovered the top cap section of the PCV housing had burst and a few last wisps of smoke were coming out of it. See pic:

20140416_160600.jpg

Further attempts to start the engine resulted in strange, erratic cranking and noises I can't even describe with words. No start, obviously.

I realize that by replacing the sensor I could have inadvertently disturbed other systems (damaged wiring, etc.) but nothing seems amiss. These particular symptoms were definitely not present before the repair.

To avoid a long, convoluted post, I won't bother with every minute detail of my repair process in the main post. My hope is that someone has seen this before and can point me in the right direction. I'll post more info if needed.

Thanks in advance.

 

Sounds like...a backfire into the upper intake which blew out the Pcv unit......just guessing, that is the only thing I could think of..did you take any plug wires off??? If this was the case, pressure came up through the valves into the upper intake.

 

Since you said its running Hot....
I don't know how many miles you have on it...
But I suspect the upper intake is warped out (Its plastic)...
I would recommend, Replacing the upper intake and Lower intake replacing the Gaskets...

The 3800's are known for them wearing out etc... Instead of the factory doorman gaskets we recommend you use the Aluminum replacement gasket... But unfortunately.. the upper intake replacement is also plastic....
But the Aluminum Gasket will eliminate the upper from warping again.

Once these engines get hot 1 of the other places the intake takes a hit is at the PCV pipe.

 

My first thought, since you replaced the Crank Position Sensor, I believe you need to have a relearn done (and a GM Tech II is required to initiate that).

But this does not explain black smoke and the PCV blowing out. That means there was a build up of pressure. I have a thought, bit of a guess. There have been some known cases of the plastic UIM exploding due to a fuel pressure regulator failure allowing fuel/vapors to build up in the intake, next start of the car ignites them and blows the UIM up. Pull the thin vac line off the regulator (found on the fuel rail). See if it has fuel in the line or a HEAVY smell of gas. If so, replace the regulator IMMEDIATELY!

 

Thanks for the replies, guys. I'll follow up on some of your suggestions later today and let you know what I find.

 

Good info, never heard that one.

 

^^^ This is correct ^^^

You didn't accidently crimp one of the wires during installation of the sensor or the cover? If the wires aren't routed properly it is easy to do.

 

Sorry to necro this, but I feel it's my duty to update this for anybody searching this problem.

So... shortly after my last post I did a lot of research and couldn't find any more info about the cause of this issue. I had always intended to pull everything back apart and start over, but discouragement and procrastination got the better of me so I put the car in the garage and sulked about it for a year and a half.

A few days ago I decided it was time to do something about it (or at least make an attempt to see where I stood). I pulled the harmonic balancer off and discovered a major mistake.

Apparently I hadn't been observant enough to notice a Woodruff key on the end of the crankshaft and a keyway slot on the harmonic balancer. Yep, I had it completely misaligned. I had made some rudimentary marks on the pulley and block and thought it would be close enough. Most of the Woodruff key had sheared off, but there was still a small piece of it left towards the engine that I couldn't remove.

Rather than getting into a long, expensive repair (likely with a tow to a shop), I decided to to reinstall everything correctly and hope that the small piece of the key was enough to align and secure the balancer. It fired right up and ran fine.

Long story short, an incorrectly installed harmonic balancer will somehow cause the symptoms I described in the main post. I'm not engine-savvy enough to know WHY, but nevertheless...

Anyway, I hope this helps somebody in the future.