2008 silverado 1500 5.3L cyl. #7 misfire, stabilitrac off, service bra

ram849 · July 13, 2016

I have a 2008 Silverado that had a stabilitrac problem, and the service brakes came on. Then I got a code p0307, cylinder 7 misfire. After changing all of the plugs all of my engine faults went away. My engine purrs as it should and the transmission shifts smoothly again. It was really jerking into 2nd. But I don't know why changing the number 7 plug took care of everything. Has anyone else experienced this ? I'm not complaining, just confused as to why that was causing the other problems. This is more for an informational post than anything. ram849

elamigowapo · July 13, 2016

Im glad you fixed your problem, how has your truck been running since? my truck is an 08 as well with the 5.3 engine and it is doing the same. I am just waiting for the spark plugs to arrive. As far as your question goes I heard that when those messages come on its because your truck is going in to some sort of limp mode and does not necessarily have anything to do with your stabilitrac system.

MaverickZ71 · July 14, 2016

This happens a lot. Usually not really a Traction Control or Stabilitrak problem. Most likely fouled spark plug(s) fouled by excessive oil usage caused by AFM and/or piston rings.

LTZDaddy · July 15, 2016

This happens a lot. Usually not really a Traction Control or Stabilitrak problem. Most likely fouled spark plug(s) fouled by excessive oil usage caused by AFM and/or piston rings.

THIS!!!!! [emoji106]

We have an 05 Envoy Denali 5.3 with AFM and it has been a nightmare since day one as far as AFM is concerned.

Way back when it was under warranty they were replacing spark plugs and replacing plug wires and telling us that was what was wrong with it.

Of course after it ran out of warranty we found out that due to AFM it will carbon foul rings and foul plugs.

On ours I changed all the plugs twice after the dealer changed them once.

And the number one plug I had to change about every 2 oil changes.

My wife drives the truck (or drove the truck up until the last couple of months) back and forth to work and she has got stranded a couple of times trying to come home with it going into hard limp mode.

What we did to solve it is she keeps a code reader in the truck, she keeps two extra spark plugs in the truck, a length of vacuum tube, and the tools needed to change out the spark plug. So when it goes out on her I would just go meet her wherever she was and change the plug there... Which I've had to do twice.

OTOH I have changed the plug here at the house like I said... About every 2 oil changes and it has 163000 miles on it now.

The only thing that I have found (which has been within the last year actually) is by moving to 20w50 oil it doesn't foul the plug out near as badly and it really doesn't hurt performance and definitely helps oil pressure.

GM has a TSB on the issue. On ours we got lucky it was the number 1 plug. However on others like yours for instance it can be number 7. And God forbid it's an even number plug on the right hand side of the engine because they are a BEAR to get to!!!

The new GM solution is to pull the top of the engine apart, pull the lifters out, find the bad cylinder (or cylinders) hone it/them, re-ring, put new piston(s) in and possibly new valves then put it back together with a newly disabled AFM system.

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