Rough idling

[Olumide]

My Toyota Avenisis T3-X (2005) suddenly started rough idling badly last week.

I had it fully serviced this week. My mechanic even did a diagnostic check done today but nothing turned up. He even did an ECU (I think) reset but none of that seemed to fix the problem.

The idling is sometimes so bad that the engine stopped a couple of times. When on my drive the RPM routinely goes down to 400 before bursting back up to 1000.

What can I do?

- Olumide

Birmingham, UK

[TonyHSD]

What engine is the car and mileage?

Rough idle is typical for dirty throttle body, maf / map sensor, if there are no faults stored. 

[Olumide]

Its a petrol engine. Mileage 152k.

I gave it a motorway drive today and it was much smoother from the get go. Not sure if it matters but I've only been doing short city drives for over a year (since we got a newer car).

I topped it up with premium petrol today and I'll be going out of town with it tomorrow.

[Olumide]

Update:

The car won't start today. The doors open but dashboard won't light up completely.

The day the problem originally started the vehicle had lost power completely and I had to jump start it. It was then that the rough idling started.

Could it be a faulty alternator that's not working well at low RPMs and also not charging the Battery properly?