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Knock sensor

Tiny
RCA195203
  • MEMBER
  • 1998 GMC SONOMA
  • 4.3L
  • V6
  • 4WD
  • AUTOMATIC
  • 230,000 MILES
I would like to know if my knock sensor can alter my timing? Everything else is either new or adjusted where it is supposed to be, but my timing marks are off!
Monday, November 5th, 2018 AT 11:55 AM

97 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

Which timing marks? The one with the chain or the distributor?

No, the knock sensor will not effect the timing at all. The PCM will change the timing internally when it detects pinging. If you have a scan tool, you can monitor the knock sensor pids.

Roy
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Monday, November 5th, 2018 AT 2:57 PM
Tiny
RCA195203
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Well the only reason that I suspect the knock sensor is because nothing else makes any sense as to why the timing marks will not line up. It's on the #1 TDC and the rotor is pointing to the right mark on the distributor. Compression is good, fuel pressure is good and I have spark on all plugs. What else could it be?
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Monday, November 5th, 2018 AT 3:55 PM
Tiny
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Okay,

What is the exact fuel pressure?

A clogged catalytic converter will cause this as well.

Roy

https://www.2carpros.com/articles/how-to-test-a-catalytic-converter
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Monday, November 5th, 2018 AT 4:00 PM
Tiny
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I do no know what the fuel pressure is because I had put it into a shop and told them to see if they could figure it out. At $115.00 an hour, I could only afford a couple of hours and they gave me another half an hour for free and said that I have spark, fuel, and compression. And said that it is sounding like something mechanical. They said to check the valves which I pulled the valve cover and seen that everything seem to be working like it should. They also said that it could be the cam lobe on the #6 being wore out because that is the cylinder where the misfire is. I get two codes from the scanner, P0300 and a P0306. How does the catalytic converter mess up my timing? And there is a rattle in the cat area which I knew of but I did not think that would cause the timing to mess up.
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Monday, November 5th, 2018 AT 4:42 PM
Tiny
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300 is common for low fuel pressure.

Timing is controlled by the chain and the distributor. Did they check that? Did they check to see if it jumped time?

The rattle in the cat could be it is broken inside and clogging up the exhaust. If it is blocking off the exhaust, it will not let the engine breather and it will not start.

Roy
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Monday, November 5th, 2018 AT 5:13 PM
Tiny
RCA195203
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  • 69 POSTS
I put the chain and gears on and made sure the dots were lined up.
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Monday, November 5th, 2018 AT 7:16 PM
Tiny
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When you removed the valve covers, were all the valves moving the same distance?

I would also back up and recheck the fuel pressure as well. Low fuel pressure will do this as well.

Roy
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Tuesday, November 6th, 2018 AT 3:05 AM
Tiny
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I will, but would low fuel pressure cause just the #6 to misfire? If so, how?
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Tuesday, November 6th, 2018 AT 8:06 AM
Tiny
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Yes it will. Not enough fuel to fire the cylinder correctly.

Roy
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Tuesday, November 6th, 2018 AT 9:52 AM
Tiny
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I got under the truck today and the catalytic converter is rattling pretty bad. So when I get enough money up to get another one, I will change it out. I do not have a fuel pressure gauge but maybe I can rent one and see what it is. If is where the book says it should be, what then? And what can altar my timing mark by at least 10 degrees. Is that something that is needing a computer to readjust?
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Tuesday, November 6th, 2018 AT 12:57 PM
Tiny
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Where are you seeing the timing change?

Yes, you can rent one at a parts store.

Roy
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Tuesday, November 6th, 2018 AT 1:21 PM
Tiny
RCA195203
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The harmonic balancer mark is not inline with the ear mark on the timing cover. Looks like it is 10 degrees out. But no problem with starting up or turning off.
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Tuesday, November 6th, 2018 AT 1:54 PM
Tiny
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If you line it up with TDC on the pointer, where is the rotor pointing?
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Tuesday, November 6th, 2018 AT 1:57 PM
Tiny
RCA195203
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I have two marks on the distributor, one says 6 and the other 8. I have a 4.3 so it is the 6. I also have two timing marks on the balancer, the book says to use the one on the left standing in-front of the truck as the timing mark.
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Tuesday, November 6th, 2018 AT 3:08 PM
Tiny
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Okay, did you pull the number one plug and verify it is at top dead center and the line on the pointer is correct?

Roy
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Tuesday, November 6th, 2018 AT 3:25 PM
Tiny
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Yes, several times.
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Tuesday, November 6th, 2018 AT 5:03 PM
Tiny
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Do you have a scan tool that can read the cam retard reading for the distributor or the cam sensor? It should be close to 0.

Roy
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Tuesday, November 6th, 2018 AT 5:09 PM
Tiny
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I will look at it tomorrow but I do remember seeing it before and it said 21 degrees.
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Tuesday, November 6th, 2018 AT 8:54 PM
Tiny
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This is the biggest problem I have that it is out that far from 0. Do you know if this system requires a scan tool of some kind to set the timing.
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Tuesday, November 6th, 2018 AT 8:56 PM
Tiny
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The scan tool lets you see the timing. You adjust the timing by rotating the distributor to get it as close to 0 as you can.

Roy
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Wednesday, November 7th, 2018 AT 2:27 AM

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