engine hunting at cold idle

[Robertjp]

This is baffling me,

Starting from cold, engine will oscilate at idle around 3/400 rpm, from 700 ish. Its a definite and regular pattern.

Just replaced battery, she did it before and after.

I Follow the warm up procedure, start her up with minimum revs, it oscilates, takes her up to around 2000 rpm to get oil moving for a few seconds, then back down, and she stops oscilating and idles properly...

Any ideas?

Rob

[s6boy]

In my experience quite normal and nothing to worry about. I always keep revs between 1300-1500 rpm on first start up for 20 or so seconds to get the oil moving. This stops any hunting but still idles a little too low so never leave it any longer than to get out to close the garage before driving off.

[stimshady]

i had my idle adjusted at TVR Barnet a couple of weeks ago, it was running only at about 700/750 when hot, and when cold it never started properly as idle was too low, always 'lumpy' and stalling itself for the first minute or so (with noticeable spikes, jumping up and down prior to stall).

anyway, it starts from cold no problem now, no stalling and no signifant spikes/falls in RPM on idle either. Might be what you need?

Edited by stimshady on Tuesday 5th May 22:28

[Whitey]

there is no cold choke circuit on the engine, so hence with a bit of heat in it, it will start to idle better.

[VARLEYHYD]

Just needs a service and/or setting up correctly, should idle from cold or hot.

G

[Robertjp]

Think i have worked out what it is and i reckon its me...

Think its the electronic cold revs limiter, think i need to wait a couple of seconds before gently taking her up to 1500 rpm to get the oil moving, i was being a bit keen. The sine wave characteristic is the limiter backing off the ignition i think to stop over revving at low temp / pressure, i didnt realise that kicked so low at start up.

Started earlier with just a feather on the throttle, waited a few seconds then rev'd gently and pulling away, no hint of trouble.

So, i feel like a tw*t for asking so many questions!! Trying to avoid speed 6 paranoia but i see i have caught it already... !!!

[stimshady]

ideally you want no throttle whatsoever when starting, hot or cold. would probably still look at getting it setup properly.

[sidewayz]

Robertjp said:

So, i feel like a tw*t for asking so many questions!! Trying to avoid speed 6 paranoia but i see i have caught it already... !!!

No need to apologise,we have all been there!

[WorAl]

my engine used to cut out now and then and spiked when idling. I tool it for service and its perfect now, starts no problem without throttle and idles smooth, both cold and hot. if yours still does this it may need servicing.

[Robertjp]

Just has been serviced, although it was by the place i bought it from, and i concede all services are not equal, but im speculating so enough of that.

It will idle OK (not brilliant, but ok) now im getting the start-up right

Edited by Robertjp on Thursday 7th May 12:33