2003 sentra can't speed more then 45 mi

Question

My 2003 sentra can Not speed more than 45 mi had the check engine on went to get the diagnostc and it only show P0300 miss fire cylinder change the spark plugs and now its showing the code for the variable timing selenoid, also clean the throttle body unit and the MAF sensor can't reset the check engine and car still not speeding more than 45 mi

Answer 1

What is the exact code number you got now? how is the engine oil level and condition?

Unfortunately there are many things that could cause that symptoms. I suggest starting by performing a compression test, make sure the engine oil is OK .