coil pack

hello all im new. i recently purchased a 02 trailblazer with 107,000 miles from my inlaws, and it has been nothing but trouble. it had a ses light on and was running rough. so i took it to a shop called christian brothers where my inlaws had had some previous work done on it. for 80.00 they ran what they called through diagnostics on it. there estimate came back at 1300.00 covering everything from wipers to spark plugs etc.. i paid the 80 and brought it home, 1300 is just out of the question. the problem that concerned me among the list was a coil pack on cyl number one. so i replaced it. still running rough. so i thought disconnect the neg. terminal on battery reset computer. that worked, i hooked battery back up started it up and it runs great. called my wife to brag and she asks me so how does it run with the ac on? let me check, i turn the a/c on and we are back at square one running like crap, ses light on, me upset. i need help. i have an 02 s10 with 108,000 miles that i am very mean to and in 5 years it has never given me as many problems as this trailblazer has in one week.

Welcome to AF.
Codes do not clear by a battery disconnect.
You need a scanner to clear or get codes.
Did they give you any code no when they checked it.
Or did they run a fuel pressure check?
If not call them back and ask for what code no they got and post back code no.
Also some parts places will give you a free code check
But just get codes and post back before you by any parts.
At 107 K if it has never tuned up that may be a good place to start.

p0301b cylinder #1 misfire in history and pending. thats what it says on my estimate

If it is P0301 then there is a detected misfire on #1, this can be ignition, an injector, a plug or even an internal engine problem, to start with a leak down or comparative compression test should be done, I assume the plugs are the correct ones and in good shape. This type of issue requires some comprehensive diagnostics.

in the notes it says the coil pack on cyl 1 was moved to cyl 2 which moved the problem to cyl two

Did they switch it back or is the miss now on no cyl 2?
Yoy need to rescan to see what it is doing now?

ok i know it was said that battery disconnect should not do anything but, i disconnected the battery and swapped the coil pack that i removed from cyl. one with the cylinder two coil pack. reconnect the battery turn it on, runs good no ses light. just like earlier. turn on ac, and the idle starts dropping and jumping tturn it off and it idles fine. this is the same thing that happened earlier only i left the ac on for a while when the idle was jump dropping that caused the ses light to come back on and stay on and the truck to idle rough even if the ac was off

took it out and drove it, 5 miles on freeway at 65 to 70 mph then took stop go streets back home 10 miles the last8 or 9 with the ac on full blast and it ran smooth as a top i dont know what the deal is. no ses light as of now. im going to take it out tonite we will see what happens.

Could be a connection/plugin on coil or injector.
I have had some that wer not pluged in good or making connection.
Also after a battery disconnect it takes some time and driving for the PCM to reset and learn idle and other settings
Let us know how it goes.
MT

if the problem was on cyclinder1 originally and they moved the coil pack to cyclinder2 and then the problem began there. to me that seems to be a bad coil pack. i would replace all spark plugs, plus that bad coil pack and maybe even do the throttlebody cleaning and then see how it runs.