Technical Lumpy Idle

[Paul500 Clutch]

Morning all. Pulling teeth on this one.
Hopefully someone can help PLEASE.
500 1.2 Petrol manual 2012. Drives perfectly.
As soon as I’m off the throttle the tick over is lumpy. Misfire sort of lumpy. The rev counter is fairly stable at the same time and every 10 secs or so it will have a little cough and then settle to a steady lumpy idle.
It’s had:
Plugs, coil pack, rail and injectors, map, cam position and crank sensors, Virgin ECU, all 8 exhaust manifold bolts and gasket, pre and post oxygens, battery good, throttle body and still the same.
No vacuum leak idles at 45kpa.
The only thing I can do to hear it running perfect is unplug the throttle body. Idles perfect. As soon as code cleared back to the same.

 

[John202020]

Does your car have ac? If you leave it on is it any better?
Also has the car had a new engine earth strap?
My old Mazfa idle woul get upset if you had the battery off took a month to settle down

 

[Paul500 Clutch]

Does your car have ac? If you leave it on is it any better?
Also has the car had a new engine earth strap?
My old Mazfa idle woul get upset if you had the battery off took a month to settle down

If I have the AC on it raises the revs very slightly and runs smooth.
Haven’t changed the strap but have had it off cleaned up and refitted.

 

[John202020]

Personally I'd never switch the ac off, ever, if this sorts it it's a cheap fix?

 

[Paul500 Clutch]

Not really sorting it though is it. More like putting a plaster on it.

 

[steveras57]

Not really sorting it though is it. More like putting a plaster on it.

did you say you changed the throttle body?

 

[Paul500 Clutch]

did you say you changed the throttle body?

Yes changed it. Still same

 

[steveras57]

Yes changed it. Still same

Considering everything else you have changed and the fact it works ok with the air con on id think its an ecu issue why did you change the old one for the new virgin one? was it running ok with the old one and do you still have it? if so put it back on and see what happens! .
Were the replacement injectors new or used?.
I had a real lumpy idle which i solved with NEW injectors!- replacement used ones are a bit of an unknown quantity unless you have a way of testing for function and spray pattern etc!.