I have a 99 sable OHV 3L. It has a misfire on cylinder 1. Coil pack, plugs, wires and injector were changed, the fuel rail system was cleaned. Don't notice the mis when I drive it. I was told it could be caused by bad PCM. It now started to develop a trans problem. When the speed odometer reaches 40 mph, it gose wacky then stops working. Soon after that the trans starts to slip once and a while. My question is can all this be caused by a bad PCM? Thanks in advance

 

Seeing how you don't notice the miss when driving tells me that the miss is an idle problem. I would look for a vacuum leak (bad vacuum hose, intake gasket) near the #1 intake that might be leaning out that cylinder.

For the intake gasket spraying something like carburetor cleaner the intake gasket and head will cause the engine idle to speed up if it is leaking. I'm not familiar with your particular engine, but I would start checking for any vacuum hoses first.

 

Also forgot to mention that I did a compression test all cylinders were equal around 116. I also changed the hoses and egr valve. Thanks for taking the time to trying to help Bulldozer