Engine ‘hunting’

[Graaf]

I have an S2 fitted with an Everest chip.

The engine runs fine under load but when I lift off the accelerator it feels like it’s ‘hunting’.

Any thoughts as to what could be the cause?

Thanks

[Simon_P]

You haven't given much information. But for a shot in the dark try temporarily disconnecting and plugging the vac hose at the EGR valve.

[Graaf]

Simon,

Not being very technically minded I'm not sure of what else to say, sorry!

The car is 1995, 54,000 miles and fitted with a PNM exhaust

What other information would you think would be helpful?

[Simon_P]

Could you elaborate on hunting - can you describe what you hear, feel, see, smell? How strong, frequent, soft, loud? Throttle position, revs, gear, roadspeed?

[Graaf]

Oh,right. The engine is jerky as if it's missing, running rough. But as soon as I accelerate it runs fine.

[Simon_P]

Great! That narrows it down to fuel or ignition!

[Tuga2112]

Great! That narrows it down to fuel or ignition!

is it not possible to be a vaccum leak as well ? with the computer trying to compensate ?
or timing ? when my timing belt slipped a few teeth it was extremely rough on iddle but revving higher it was not noticeable that something was very wrong.

[Simon_P]

Yes, I was being ironic, it could be absolutely anything!

Everything on an engine comes back to fuel (mixture if you prefer) or ignition, but there isn't enough information to do anything other than guess.

Your guess is vacuum, mine is EGR (based on vacuum as it happens). But it could be IAC, fuel pressure regulator, leaky injectors...

I suppose we could add mechanical issues like a worn engine mount.. Anyone who had an old mini would know the symptoms of a loud bang from behind the speedo and the kangaroo effect of a worn engine stay.

[Graaf]

Great! That narrows it down to fuel or ignition!

That was my thoughts as well but I just thought it may be a known problem.

By the by I took off the vac pipe but no difference.

Thanks anyway