2008 Tahoe P0300, Rough Idle After Work

[davidkramer]

Hey ya'll I had my oil pump, pickup tube, lifters and all gaskets replaced on my 2008 Tahoe 4WD with 120k miles on it. About 5min after driving it, I had a service traction control/stabilitrak light and P0300 light come on with a rough idle. Looking at my computer, it is saying Cylinder 1 and 7 are misfiring (7 worse then 1). We then replaced the plugs, wires and ignition coils and still the same exact codes and symptoms. The fuel injectors are all coming back as OK on our scan computer as well.
Anyone have any additional ideas? We drove it the other day and when it warms up/highway speeds, the light goes off but immediately comes back on when you are sitting at a light.

 

[Dustin Jackson]

@davidkramer Did you have a lifter failure or why did you do all that work?

 

[davidkramer]

@davidkramer Did you have a lifter failure or why did you do all that work?

Yes. I had lifter noise for the past 6 months getting worse and I had low oil pressure that rose after driving, indicating the o-ring failure. Instead of just replacing the failed lifter and o-ring, I had my friend do the oil pump, all lifters, head gaskets, plugs, coils and wires while he was there.
We troubleshooted a bit more: Cylinder 1 is misfiring a little and Cylinder 7 is misfiring a lot. When you rev it, the misfire goes away. We swapped cylinder 1 and 7 plugs, wires and injectors with others and it was still misfiring, so that isn't the problem. He put in some seafoam and Lucas oil stabalizer to see if it will help if one of the new lifters was sticking, but it didn't do anything. We still have the code. He is going to take apart that head next Friday as he said it is pointing to a bad new lifter.

 

[strutaeng]

You didn't remove or inspect the camshaft? What if one of lobes for the intake or exhaust is wiped out? I'm just asking. Did any of lifter wheels have any damage?

 

[Dustin Jackson]

@davidkramer I would inspect the cam too

 

[bfishing]

Hey ya'll I had my oil pump, pickup tube, lifters and all gaskets replaced on my 2008 Tahoe 4WD with 120k miles on it. About 5min after driving it, I had a service traction control/stabilitrak light and P0300 light come on with a rough idle. Looking at my computer, it is saying Cylinder 1 and 7 are misfiring (7 worse then 1). We then replaced the plugs, wires and ignition coils and still the same exact codes and symptoms. The fuel injectors are all coming back as OK on our scan computer as well.
Anyone have any additional ideas? We drove it the other day and when it warms up/highway speeds, the light goes off but immediately comes back on when you are sitting at a light.

Hi! I have just helped a friend clear stabilitrak and violently shaking engine by removing and cleaning the throttle body also changed the throttle body sensor which may not have been needed but he's running smooth once again, check that if you haven't done so as yet!
PS I also found a broken wire on the sensor connector

 

[davidkramer]

You didn't remove or inspect the camshaft? What if one of lobes for the intake or exhaust is wiped out? I'm just asking. Did any of lifter wheels have any damage?

My friend did the work. I asked him and he said "the camshaft looked fine and none of the push rods were bent". I will ask him about the lifter wheels in the AM.

 

[davidkramer]

Hi! I have just helped a friend clear stabilitrak and violently shaking engine by removing and cleaning the throttle body also changed the throttle body sensor which may not have been needed but he's running smooth once again, check that if you haven't done so as yet!
PS I also found a broken wire on the sensor connector

Thank you. Did it have any specific codes on it that you remember? I will do this in the AM

 

[bfishing]

Thank you. Did it have any specific codes on it that you remember? I will do this in the AM

I didn't log the code, I remember the problem did state throttle sensor was a problem with stability also an issue, I forgot to mention I also went under driver side an cleaned the ground wire connected to frame underneath, once I repaired the broken wire from sensor the motor shook, so then I proceeded to clean throttle body, both problems cleared away...

 

[j91z28d1]

wait.. did you replace the afm lifters with non afm lifters? or new afm and if afm what brand?

I've seen threads where guys put new Amazon/ebay(China) afm lifters and they fail from the first start having to do it all again. the only acceptable brands are oem gm, not bought from Amazon. either dealer, gm parts direct or rock auto seem to be the only trusted source these days. or millings, the company that makes the oil pumps.


before you pull the head, pull the valve cover and see if a rocker on 1 and 7 is loose meaning the lifter is stuck down.

good luck..