Misfire

[XfireZ51]

It's possible the O2s "drop out", meaning the signal goes to 0, but that would suggest a lean condition to the ECM. I saw that happening on a number of my logs until I finally changed out the Bosch 02s for AC Delco. Then the signal was solid as a rock.
The symptoms that this is happening at idle and below 3000rpm suggests it's happening at higher vacuum/lower MAP. So question is whether there's a vacuum leak causing a lean condition and so a stumble?

If u have Bosch 02s, I'd swap them out for the hell of it.

[ZRXMAX]

Solid recommendations ! Don't know why I didn't think about these a while ago. Bad 02 sensors can really cause weird things to happen. Will try it tomorrow. Thanks

[ZRXMAX]

I found the problem... cam cover bolts adjacent to the #1 spark plug were getting loose. Lesson learned!

[Dynomite]

Originally Posted by ZRXMAX

I found the problem... cam cover bolts adjacent to the #1 spark plug were getting loose. Lesson learned!

Which Cam Cover Bolts?
How Loose?

Exactly how does a loose or a couple loose cam cover bolts cause a misfire?

Was Number 1 Spark Plug Port full of oil (were the Cam Cover Bolts THAT LOOSE)?
That Loose as to cause the Cam Cover "O" Ring to fail on Number 1?

[A26B]

Originally Posted by ZRXMAX

I found the problem... cam cover bolts adjacent to the #1 spark plug were getting loose. Lesson learned!

You're about 3 weeks early. April Fools day isn't for another 3 weeks yet, but you sure got me on that one.

[Dynomite]

Originally Posted by A26B

You're about 3 weeks early. April Fools day isn't for another 3 weeks yet, but you sure got me on that one.

I am confused

Two issues reported recently (This Misfire issue and a Pilot Bearing or Throwout Bearing failure at 20K miles) and my issue with a cracked impeller on a NEW Water Pump ....I am thinking ANYTHING IS POSSIBLE

The Cracked Water Pump Impeller (NEW WATER PUMP) issue I caught right away but did take a bit of diagnosis to eliminate an Air Locked Water Pump as I had just drained Coolant.

Damn.....I am not even looking at this Forum on April Fools Day or for a week after

[ZRXMAX]

Originally Posted by Dynomite

Which Cam Cover Bolts?
How Loose?

Exactly how does a loose or a couple loose cam cover bolts cause a misfire?

Was Number 1 Spark Plug Port full of oil (were the Cam Cover Bolts THAT LOOSE)?
That Loose as to cause the Cam Cover "O" Ring to fail on Number 1?

When I was putting the plenum back on for the third time and holding a 40 torx in my hand I looked at those bolts and thought... I wonder if they are loose?

Indeed they were ! I estimate they might have had 10 lbs of torque on them as they sat. Keep in mind their was no oil or any leakage of anything to be seen inside plug hole # 1.

So, I looked up the torque number and applied it.

Keep in mind I had reported early on that the #1 boot kept coming out. When I would re install it the connector would emit that little click that indicated it had slipped into place at the top of the plug.

To get it off required the same amount of effort as any other plug. So, I have to assume air pressure was building up and blowing it off.

I will see what I can come up with for April Fools !

[Z51JEFF]

You have more patients than I do. After the first plenum pull,if the problem is still there I'm throwing new parts at it.🤑

[ZRXMAX]

Originally Posted by Z51JEFF

You have more patients than I do. After the first plenum pull,if the problem is still there I'm throwing new parts at it.��

I did throw new parts at it... actually, I was recycling parts that were stilll good but were removed as preventative maintenance. Coil packs, ECM, chip

inside ECM, map sensor, plug wires, spark plugs... also checking fuel pressure several times, and, new O2 sensors were installed. We were down to 3 items. The module under the plenum, crank sensor, or cam sensor.

We also did a data log on a short 4 minute run and everything appeared to run in the normal range... so... the head knocking was getting painful!

[Z51JEFF]

The cam position sensor will give a code,can't remember what it is. The full power will be cut,check engine light will come one and the car will run like its starved for fuel,at least that's what mine did but it didn't have a miss.