Strange Lumpy idle.
 

Ok, my silvia has always had a lumpy idle, it starts up fine but as soon as she's warm she hovers at 700rpm and flutters up and down, only about 50-100rpm at the most, she's always done it, she revs fine and pulls fantastic, i assumed it was old and tired spark plugs so today i finally got round to fitting a new dizzy cap, coil lead, ht leads and spark plugs set @ .9 gap, the idle is still lumpy, so ive got in contact with the guy who owned it befour hand and he mentioned a cam re-profile? he mentioned that this causes the car to tick over lumpy.

Befour i get loads of questions i'd just like to say the car never stalls, nor does it effect drivability, she pulls fantastic and doesnt spit out any smoke, well apart from the dying turbo:rolleyes: it never causes grief but i just want to know if this is a problem?

And i want to say thanks to all who have helped me in the past, i aprecieate all the help you guys have offered.

never got lumpy idle with my piper cam, but i had the same problem on my 2nd s12, but it would come and go, i had the same problem a month ago on this s12, but its cleared up its self.:confused:

Are you getting any fault codes showing on the ECU ?
I had a similar problem when I first re-built my ca18et, the throttle valve switch needed adjusting if I remember correctly.
Regards,
Ian.

Whats a fault code do then?:confused:

Oh dear :trout

When you run the "self-diagnostic" function on the ECU it will give you codes for any problems that it may be sensing?

Search the forums for "ecu diagnostic" and I'm sure you'll find the instructions

I'll give that a try in the morning, thanks.

Let us know how you get on with the self-diagnosis :D .
Regards,
Ian.

The ECU prob wont show any codes. I would start with some decent HT leads, a new dizzy cap and rotor arm, and check the CO2 emissions at an MOT station

it's your idle air regulator. mine does the same thing. it won't affect anything :D

I just find a faulty air reg used to stop it idling fast when cold as I assume they get all gunged up.