2011 Nissan Sentra - Bad misfire

I have a 2011 Nissan Sentra that is misfiring very badly (shaking, cel flash, burning smell) and i went to get the spark plugs changed and he said that the cylinder 3 was very bad but after replacing them all the issue is still there and there was nothing else they could do as it was a motor problem. The car is throwing up codes p1722 vehicle speed circuit, p1701 power supply circuit, p0303 cylinder 3 misfire, and p0300 random cylinder misfire. If it matters the previous work i had done on it were a battery replacement, an oil leak, and an exhaust leak. A week after fixing all of these the misfiring issue came up.

A flashing CEL means turn off your engine before damage occurs.

None of which would fix a mis-fire.

So you told the mechanic to change the spark plugs, he told you #3 has a cylinder problem, but you did this anyway? So money tossed at the problem hoping it will go away. Even when the mechanic told you what was wrong. It didn’t fix the problem did it?

The engine (motor) has a problem that must be fixed if you want the car to run correctly.

None of the other codes matter at this point.

Can we assume there were some tests done to back up this statement?

compression test?

cylinder leakdown test?

Or at the very least, a relative compression test with a scanner?

Another question . . . did you pay for a diagnosis?

or did you only pay the shop to replace the plugs?

those were previous issues that happened before the misfires, i was wondering if any of those issue could have been related to why the misfires started to occur, or if they were totally unrelated

he only charged me for the plugs themselves and waived the labor fees due to this problem. I brought the car there and he thought it was a spark plug issue at first and then changed them. He only charged me the price for the plugs and not for the labor since the plugs turned out to not be the issue. I had no idea about what the actual problem was until afterwards.

im honestly not sure what tests they did to check for what it could be.

I was only charged for the plugs and he said id have to take it somewhere that does motor work.

There you go. Dealer does not have the skills or want to do it. Go to next shop.

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We haven’t been told it was the dealer. Probably not a dealer.

The person seems not to be willing to get further into it. That’s good to know at the outset.