I have been perusing the forums trying to find a solution to my issues with my Suburban but there are so many other underlying issues with the posts I found that I am not sure which solution applies.

For the past month or 2, my Suburban starts rough. On the initial crank, it seems fine but within a second or 2 (when the RPMs drop), my whole vehicle shakes and shudders, almost like it is not running on all cylinders. I let it idle for a minute or two and back out of the driveway. When I put it in gear, you would almost think it was a diesel by the sound the engine makes. If it is cold in the morning (45 or below), it will still idle rough at stop signs and traffic lights (and lights will dim with each shudder because the RPMs are dropping) until the temp gauge reads around 200. Once the roughness resolves itself, it won't do it again unless it has been sitting for over 8 hours (like when I leave work) and even then, it is not the same as if it had been sitting overnight. I have around 115K miles on it and have always had every recommended maintenance (just had the fuel system maintenance done and that did not fix the problem). The check engine light is on and it is giving the code for the O2 sensor but the tech said that this sensor would only affect gas mileage but did not lead me to believe that it would cause the engine to run this rough. I will be taking it back to find out exactly which sensor it is and having it replaced but again, I am not under the impression that this sensor is what is causing the issues. I will be getting a newer vehicle in the next year so don't want to invest thousands of dollars to trouble shoot the problem.


On a side note, one thing it does also that is annoying is that when I turn it off, the driver's seat starts jerking and shuddering like it is trying to quickly adjust (they are power seats obviously).

Any suggestions on what to start with?

 

You could try to reset the electrical system (not sure if that would cure your engine issue but might help with the seat).

Disconnect the negative battery cable and leave it off for several minutes. Reconnect the neg cable and turn the ignition to "on" but dont start the engine. You'll probably see some light blinking etc while it cycles. After a minute or two you can then start the car.

Regarding the engine, what's your coolant level like?

 

Welcome to the forum.

Might check fuel pressure.

 

Any luck, mine does the same thing without the seat problem lol?

 

Don't know about the codes just figured it out the old fashion way. Check your intake manifold gaskets, they could be a leaking? When idling (cold) try spraying some starter fluid right along the gasket seems with the heads, if it idles up (rather highly) you found the leak(s). This is a common problem in that mileage range. GM could have used better gaskets!!! I had a Suburban do that and it ended up being the gaskets. It was worst in the morning when cold then got better as the engine heated and the expansion closed the gaskets off somewhat.

Seat: I had one operating exactly backwards, had to have the dealer reboot (flash) it with their computer. Just fuel for thought, maybe?

 

look at coils and spark plugs sounds like an igniton issue .