M6 Sputter under load when cold

Post here for mechanical and engine topics such as fuel issues, transmission problems, rough idle, exhaust, electrical issues, etc

Moderators: GRNSHRK, ron, bfons

Post Reply
User avatar
gthberg
Posts: 69
Joined: Mon Sep 07, 2009 1:40 pm
Location: Virginia

M6 Sputter under load when cold

Post by gthberg »

Having a recent issue with my 1987 M6. It starts fine, even when it's been sitting. But it sputters a bit when under load....only until it reaches operating temp. My immediate suspect is the ICV, but wanted to see if anyone had any other ideas before I dig in.

Thanks
'87 Dinan M6, Cinnabar/Lotus
'09 M3, Interlagos/Fox Red
User avatar
Brucey
6 Series Guru
6 Series Guru
Posts: 10077
Joined: Fri Apr 09, 2004 7:17 am
Location: Cambridge, UK

Re: M6 Sputter under load when cold

Post by Brucey »

other than being a potential site for air leaks (for unmetered air because it has hoses and potential leak sites) the ICV cannot affect running under load; all it does (even if it fails entirely) is affect how much air goes through the throttle butterflies and how much through the ICV; it should all be metered air either way and the fuelling should be matched to it. Air leaks (from the outside world to the inlet) are a different matter.

Rough running when cold (on a car with an O2 sensor and closed loop running) suggests to me that something is making the mixture too lean (or too rich possibly) during 'open loop' running i.e. before the O2 sensor heats up and starts working. Once the O2 sensor heats up it will control the fuelling and mask whatever faults you may have.

Very common problems are

- air leaks (unmetered air) and/or
- failed CTS and/or
- badly regulated fuel pressure

cheers
~~~~~~~~~~~~Brucey~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Post Reply