My toyota Noah has an interesting problem. It was running perfectly until I took it for kawaida service. The jerk of a mechanic could not get the oil filter out and so he decided to remove some components so as to reach the oil filter and then he put them back again. Immediately after this service, as in I did not even have to leave the garage, the car developed a rough idle. it also stutters and shudders for a few seconds before it picks up speed from standstill position. The rough idle is worse when the aircon is on or when it is in gear but stationary. A few times when reversing slowly, the engine actually goes off (the car is automatic). I have changed fuel filter, spark plugs and cleaned the intake manifold lakini problem persists. The jerk of a mechanic wanted to sell me a second hand oxygen sensor lakini I refused. The clue , I think is that it must be something he touched or removed on his way to the oil filter. Tafadhali saidieni....

Make sure all the park plug wires are snug pushed all the way in on both ends. Next check all vacuum lines around the area where he would have removed components to reach the filter and around the throttle body. Check the EGR valve and make sure its secured. These are the most likely causes of a rough idle.

you can go to Concorde motors they run diagnostics but @4K. Did he touch the IACV?

Discovered that the problem was a crack in one of the lead wires. Changed the wires and was good as new.