hey guys,

2000 jeep grand cherokee. its only running on two cylinders, got a p0303 code, shop said i probably got a flat spot on my cylinder or a hole in it. I'm not so sure cuz he didn't compression test the rest of the cylinders. replaced the spark plugs and coils, no help. i can un plug every wire to 1,2,3,5,6,7 and nothing changes, but unplug 4, or 8 and it starts to die, also has a hard time idling, real rough. what is going on?

 

I can tell you what's going on, you need to find a new shop that will take time to properly diagnose the issue instead of just throwing parts at it and giving you bogus reasons.
The code simply means there is a misfire on cylinder #3.
A full compression test would have given a lot more valuable information and would have been simple to do when replacing the spark plugs.

 

Welcome to CF!

The above is very good advise. If that's all the information the shop gave you, you wasted your money. A full complete compression test will show you the condition of ALL the cylinders and if a couple are low, should show you if the rings are bad or a valve is burnt or the head gasket is bad.

We really are just guessing without this information. If it truly IS only running on 2 cylinders, it will die when you disconnect one. It WILL run on only 2, but those 2 have to be 4 cylinders apart in the firing order. That's assuming you have a 4.7 V8.