Assistance required please,

I was driving my 2002 Hummer H1 and unexpectedly, the vehicle started to accelerate. While pressing on the brake, I immediately pulled off to the side of the road and slammed the shift lever into park.
The few times I turned on the vehicle, it fired up with a hard rev, then shutting off shortly after. Black smoke also came out of the tailpipe. My vehicle had to be towed back to my house.
A local mechanic recommended changing the PDM. I did that yesterday but still no luck. About a week ago I added SeaFoam diesel treatment. I’m wondering if that’s the cause of my car trouble.
Does anyone know what could be the problem? Any suggestions on a good mechanic near 34957 zip code?
Thank you in advance for any suggestions on this thread.

 

if diesel you might have stuck or leaking injectors. sounds like an over fueling issue hence the black smoke.

 

The Seafoam did not cause that.

 

Hope you've got it fixed by now, if not, check the PDM. Mine started to accelerate, stall, accelerate, stall. Luckily, it happened while my mechanic was testing out something else. turns out, one of the wires to the PDM melted because the PDM got too hot. Had to replace the wire harness, mount the PDM in friendlier spot, Always care a spare PDM. It takes five minutes to change and will most likely be the culprit.
Knowledge Base - Fuel

 

My vehicle was fixed. It turned out to be the injector pump. Labor and pump cost me $2,473.00. Thank you all for your valuable input. My truck is running strong.