Technical Seicento tick-over erratic

[rogerowen]

I've just purchased a 900cc Seicento (2000). It starts up revving hard then quite quickly slows to normal - which I'm told is the auto choke? That's fine but when driving in traffic and stopping at lights eta, the revs fluctuate from high to very low (nearly stalls). There's a pipe that runs from the manifold to the air filter which is in poor condition and I'm about to order a new one - but I've got a feeling that's not the problem. Anyone point me in the right direction? Cheers.

 

[David C]

Check the small oil breather that T's off of the main oil breather to the throttle-body.
When the throttle is closed it pulls air/oil-vapour through that pipe to form part of the intake air in addition to the air taking the normal route via the idle-valve.

If that pipe is flattening it will cause the revs to drop and the idle-valve will have trouble keeping up!

 

[rogerowen]

Many thanks - that sounds nice and simple!

 

[rallycinq]

There is no auto choke, there is no choke full stop.

The car is fuel injected, you should expect slightly higher revs when initially started, but not racing away.

Make sure the throttle cable on the throttle body is a bit slack. too tight at idle, and the engine will hunt.

When was the car last serviced, and what grade of oil is in it?

Cheers

D

 

[rogerowen]

Thanks, I'll take a look at that. There was very little oil in when I got the car Just on min on dipstick, I've put some 15W40 semi-synth.

 

[centoproject]

when you say you put some dose that mean topped it up ? if so i would drain and replenish with new, as for idle i would check for vacuum leaks around the intake and so on .

and welcome to the forum

 

[fingers99]

All the above.

If there's an obvious split in the breather pipe, a very temporary repair with tape might provide evidence.