vibrating at speed between 40-50 service engine soon light is now on are these

If the light is steady it means it is an emissions issue. Don't panic. Get a free code reading at Advance or Oreillys etc. They may say it is the O2 sensor. You can order a nice Bosch online. When O2 sensors stop working it causes fuel air mixture to screw up the computer per sensor reading. The emissions in a lot of Trackers are California based which means it is nit picky environmental design which will trip your computer if the upstream and downstream sensor don't fall within certain "specs". Don't go buying expensive parts from the stores you ask to diagnose, just get them to make sure they know what the code reding is so you know for reference and get a print out. I also put Amzoil in my fuel and it helped clean out the fuel system and it runs better. Then you will want to put in non ethanol gas (100% real gas). 87 is okay, 89 will help it run better. Find a gas station that sells it. It costs a bit more, but is better for the engine than 10% or higher ethanol gas which some mechanics say will cause crud to build up in the engine. This is because the powers that be don't want you to be able to drive a gas car. And is why they want you to buy ethanol gas. Only post 2012 cars that are designed for ethanol gas should use that crap. If you car is close to 200,000 miles or approaching you will probably really want to try the Amzoil you can order from same website. Check your car manual and it tells you what the light is referring to and check for routine maintenance measures per mileage. Find a trustworthy mechanic who runs a reliable small operation if anything else needs to be done. Videos on the web will show you how replace an O2 sensor if you need it. I'm telling you all this because I went through the same thing with my 99 Tracker and it's still going. Vibrates, but not nearly as bad. Still looking for other measures.