I have a 2003 gc jeep. It has over 142,000 miles. I only had 4 cylinders that we on 2003 Jeep Grand Cherokee

2003 gc jeep overland park. It has over 142,000 miles. There were only 4 cylinders. I bought a computer box, and the car still runs hard and very rough. What should I do to make al 8 cylinders run?

Asked by for the 2003 Jeep Grand Cherokee
you need to diag what the issue is 1st. mechanical or electrical
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What's a computer box? You're going to have to take it someone and have them look at it. You must have a check engine light on? What are the codes?
Well I was told the computer box is the brains for the whole car. It is electrical problem. I dont recall any codes being displayed. I have someone looking at it now. It is at a shop where I have taken a few of my cars before. He reall doesnt know what is wrong with the car. It was his diagnosis that told me to get a computer box, and now I have spent all this money and the car still runs rough and very hard. Do you have any suggestions? I do remember when I bought the car, the engine light was on, and I took it to this shop, where I have it now. He said there wasnt anything wrong, and now years later, he doesnt know what is wrong with the car. He has my car now.