Code P0306 and a misfire on cylinder six?

Tiny
AROBTAYLOR
  • MEMBER
  • 1997 FORD F-150
  • 4.6L
  • V8
  • 2WD
  • MANUAL
  • 137,000 MILES
I have a P0306 code.

I have new spark plugs and swapped spark plugs.

I have new plug wires and swapped plug wires.

I swapped fuel injectors.

I did a paper test on the tail pipe with no suction. (Good sign)

I have new coil packs and swapped coil packs.

Idle changes when injector is unplugged.

I had the harmonic balancer fell off and put a new one on before the check engine light. Check engine light came up about 80 miles later.

I'm looking for some advice or direction on this misfire.

Thanks!
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Monday, May 3rd, 2021 AT 11:40 AM

15 Replies

Tiny
KASEKENNY1
  • EXPERT
Wow. Excellent process of elimination. Plus the paper on the tailpipe shows you are "old school." So for the benefit of those that are reading this that don't know that trick, it is to test for a valve issue on the exhaust side.

If the paper is pulled into the tailpipe then you have a valve hanging open and the suction of the stroke will pull the paper in.

We still need to test for an intake valve issue so we need a vacuum gauge on the engine and let it run.

Also, we need to perform a compression check.

https://www.2carpros.com/articles/how-to-test-engine-compression

Lastly we need to monitor the o2 sensor data to see if we have a rich or lean condition. So hopefully your scan tool can monitor this.

If we have neither rich or lean, then I suspect the balancer issue will come into this.

Have you inspected the tone wheel for cracks in the teeth?

Also, below is a chart that will help with vacuum gauge readings but if you can get a video of the gauge, that will as well.

Let us know what questions you have on this. Thanks
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Tuesday, May 4th, 2021 AT 4:08 PM
Tiny
AROBTAYLOR
  • MEMBER
I did a compression test. I hit around 180 PSI in each cylinder after roughly 3 out of 8 turnovers - no loss of pressure.

To clarify, my balancer didn't fall off from the crankshaft. The pulley fell apart at the rubber seal.

I will be testing vacuum pressure today and maybe the tone wheel check as well.

Photos/videos will be attached.
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Wednesday, May 5th, 2021 AT 6:58 AM
Tiny
AROBTAYLOR
  • MEMBER
Here are the vacuum test results and freeze frame data.
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Wednesday, May 5th, 2021 AT 11:58 AM
Tiny
KASEKENNY1
  • EXPERT
No issues with vacuum. Short term is slightly rich but that would not effect just cylinder 6.

Anything turn up with the tone wheel?
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Wednesday, May 5th, 2021 AT 8:05 PM
Tiny
AROBTAYLOR
  • MEMBER
Agreed. Fuel trims were running +/-.8% on long terms on both banks before the misfires started.

I'll be pulling up the crankshaft position sensor circuit waves tomorrow.

How could I visually inspect the tone wheel? It seems to be in a tough place to see.
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Thursday, May 6th, 2021 AT 4:53 AM
Tiny
KASEKENNY1
  • EXPERT
Oh man. I like working with you because you have the ability to really diag this thing. :)

If you have a wave form of the crank pattern then you don't need to visually inspect it. That will tell us everything we need. If it is a tooth issue on the tone wheel then the crank sensor is picking up a faulty signal which will show an incorrect pattern.

If you can record the wave form for about 5 seconds of running then we will be able to see multiple revolutions to get a good view at the pattern. I have known good patterns to compare it too but they should all be pretty even square waves for each cylinder firing.

We can even get the firing order and find which square wave is cylinder 6 to look at it closely.

Just post some screen shots of the pattern and we can go from there. Thanks
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Thursday, May 6th, 2021 AT 9:22 AM
Tiny
AROBTAYLOR
  • MEMBER
Awesome! I am waiting for an Aultel AL539B OBD2 Scanner to come in the mail. It only cost $100.00, and I can catch the patterns with it. I will post the results when I can do the test.
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Thursday, May 6th, 2021 AT 11:18 AM
Tiny
AROBTAYLOR
  • MEMBER
Here is the wave form from the crank sensor.
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Friday, May 7th, 2021 AT 12:33 PM
Tiny
KASEKENNY1
  • EXPERT
Totally forgot that this engine has an inductive crank sensor not a hall effect, so it gives this type of pattern, like an AC circuit, and not a square wave.

I attached below a known good pattern so I think the scaling on your tools is wrong as it should be a 12 volt scale but that is a good pattern.

At this point, everything in the base engine operation that would cause a misfire appears to be checking out.

So did the misfire happen after the balancer issue or was it there prior?
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Friday, May 7th, 2021 AT 8:11 PM
Tiny
AROBTAYLOR
  • MEMBER
I'm relieved it's not the tone wheel. Thanks for the graph.

Misfire started after the balancer was replaced.

The crank sensor only has 2 wires. So if I understand correctly, this kind produces its own AC current. Would the low voltage cause an issue?

I'm going to be checking the wiring to the injector next. I believe I can get the Amp pattern of the injectors with the Autel AL539B.
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Saturday, May 8th, 2021 AT 4:33 AM
Tiny
AROBTAYLOR
  • MEMBER
Here are the failed monitors that I found on the scan tool. I haven't tested the injectors yet.
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Saturday, May 8th, 2021 AT 11:10 AM
Tiny
AROBTAYLOR
  • MEMBER
Fuel injector waveform.
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Saturday, May 8th, 2021 AT 6:06 PM
Tiny
KASEKENNY1
  • EXPERT
The lower voltage would not cause this on a single cylinder. I suspect that is just what the scan tool displays it as and it is not actually 6 volts. This is not uncommon on these scan tool to have scaling inaccuracies.

Can you feel the misfire? Meaning does it run poorly? Sounds like it is just setting the code because you are unplugging the injector and then you feel it misfire.

So if it doesn't feel like it is missing then we may have an o2 sensor issue.

The Delta for upstream o2 sensor monitor is interesting.

What are the o2 sensor voltages? The scan tool should have that and they should be between 0 and.9 volts.
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Sunday, May 9th, 2021 AT 8:18 PM
Tiny
AROBTAYLOR
  • MEMBER
The engine has a slight shake. I don't believe it's a dead misfire.

I see what you're saying about the code. I have reset the code or unplugged the battery after any change or swap in parts. The code will return without any tampering.

Attached are the o2 readings.
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Monday, May 10th, 2021 AT 10:02 AM
Tiny
KASEKENNY1
  • EXPERT
So cylinder 6 should be driver side second one back on this engine so that makes this bank 2. Bank 2 upstream is showing an average of.76 volts.

Bank 1 is showing.59 volts which is where this should be. It needs to be close to the middle as the lower voltage is lean and the higher close to.8 is rich.

I would swap the o2 sensors side to side and see if bank 2 remains rich or the misfire move cylinders.

Clear the codes and then drive and watch the bank 2 upstream sensor and see if it is still reading rich.
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Monday, May 10th, 2021 AT 7:40 PM

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