now it runs rough when cold.
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1997 BMW 528i Question: My check eng light came on
Answer #1Bertini's German Motors of Roseville (14 Answers) , Roseville, CA - (916) 288-9535Bertinis January 31, 2012, 14:47Enthusiast
You will need to read the codes to find out what issue is causing the check engine light to come on. Running rough may be a result of what ever is failing.
Answer #2Prestige Auto Works (171 Answers) , Sacramento, CA - (916) 550-9579Prestige Auto Works January 31, 2012, 16:40Journeyman
The check engine light will enable the technician to correctly diagnose your symptoms. Running rough or misfire is often caused by worn out spark plugs.