I have a 93 245 and I think your system is similiar to mine, so I thinks these suggestions will work. I recommend that if you are going to try to do the work yourself, you get a Bentley manual. I used to see these regularly go on eBay for around $30 (cheapest around). When the check engine light comes on, the computer should be storing a three digit code that you can access. This manual will tell you how to read the codes the check engine light is setting, and what the codes mean. The code will point you in the right direction.