the VVC k-series in the metro, sometimes when sitting in traffic the engine has a little cough.

Its like your sitting there in traffic, engine idling around 900rpm nice and smooth and quiet then completly random and very quickly sometimes it drops to 500rpm them coughs back upto 1200rpm then settles back at 900rpm.

what would cause that?

Cheers
Rob

It is just a common cold add some sinus relief and it will be fine.

I have this problem occasionally on my MX-5, although usually at speed and the dip is between 3k-4k revs. I still havnt figured out what it is.

LoL, some addative to fuel which cleans the fuelsystem often helps, I ment

What sort of fuel injection does it have ?

Could be a faulty idle actuator

clockd one - does the MX-5 use a MAP sensor, or a stoneage Airflow Meter?

Airflow meter, Mark.

I irregularly put redex through the car already bear, trying various things to get better performance/mpg out of it.

Most likely your AFM is faulty if youre getting a flat spot.

Try cleaning it as a first recourse, otherwise a new one may be on the cards

it never happens when im driving only when idling, so i think its the idle control valve, ill give it a clean this weekend.

Funny thing is my problem doesnt seem to affect the performance at all, it just jumps around for a second.

Quote from: Clockd 0NeFunny thing is my problem doesnt seem to affect the performance at all, it just jumps around for a second.

can you feel the jump in the car or is it just the rev counter that jumps?

Just seems to be the rev counter. The car itself runs smooth right through the revrange.

Quote from: Clockd 0NeJust seems to be the rev counter. The car itself runs smooth right through the revrange.

just sounds like a loose connection somewhere.

Itll either be where the rev counter picks up the info (could be the gearbox, ecu or coil)  or behind the instrument cluster.

Headgasket.  Best change it, then change it again because it will probably be due again before youve even started it.

Quote from: DEViANCE

Quote from: Clockd 0NeJust seems to be the rev counter. The car itself runs smooth right through the revrange.

just sounds like a loose connection somewhere.
Itll either be where the rev counter picks up the info (could be the gearbox, ecu or coil)  or behind the instrument cluster.

yeah, thats a problem with the revcounter/wireing not the engine.....

cant drop 1000revs wihtout the car slowing down.... wally

Quote from: soopahflyHeadgasket.  Best change it, then change it again because it will probably be due again before youve even started it.

lol yeah, that what most mechanics/so called experts would have said.