captiva

I have just fitted a 3" exhaust system to my 4x4 Cossie stage 3 and it has affected the way the fuel is burning, to the better, so now have an AFR meter and set it to 12, as suggested by this forum, at idle. Should I take more notice of the setting of 12 at idle or when I'm booting it up the road? This increased the tickover so I disconnected the Idle solenoid (or whatever) and adjusted the screw under the throttle body all the way clockwise till it won't go any further and although it was getting slower it still remains at 1200rpm and wanted it at 1000rpm. Any ideas, I dont any have vacuum leaks

tabetha

JESUS , you can't run AFR of 12 at idle, that is mega rich for FULL Throttle AFR.
It needs to be CO of 2.5% at idle, this would explain your problems, as this is like running nearly on full choke settings at idle.
Get a CO metre on there, set to 2-2.5% CO at idle when warmed up.
You cannot effectively change the AFR with the idle CO screw, it contributes to the whole scheme, but does not have a huge impact on full throttle settings, as thse are the written chip programms.
tabetha

captiva

OK so I screwed up just so I can get back to where I was, until I can get access to a CO meter, what should the AFR read on idle?

tabetha

I would put it about 14:1, STOICHIOMETRY occurs at 14.66:1.
Whatever you set it to it will change as soon as you put your foot on the throttle anyway, cossies unless closed loop tend to run on the rich side of ideal for safety.
tabetha
ps we ALL screw up from time to time.

captiva

Thank yooooooooooooooo, I have set it to 14:1 but idle problem is only marginaly better, still wrong side of 1000 rpm. Considering moving the throttle stop on butterfly if only I could get it to move.

tabetha

Sounds as though either the throttle plate is jamming or the valve is not fully closing, reconnect the iscv and see if it drops, then you will know if it is the valve, as this will stay in whatever postion it was prior to disconnection.
tabetha

captiva

When I reconnect the iscv it raises the idle speed, I thought that by adjusting the idle with it disconnected would eliminate the valve

tabetha

If the iscv with a warm engine RAISES the revs, I would check the tacho is not misreading, ford bless them did not endow the sierra's with very accurate clocks!!
Just connect up a after market TACHO to the coil.
If not then I would look at the CTS as this is the MAIN corrective factor for the mixture, and if it is saying the engine is cold the ecu(iscv) will raise the revs.
Indeed if you have not changed the CTS in the last 4years or so I would for the cost(£10) just change it anyway.
tabetha

captiva

Thanks I will, I think I should change all the sensors if not to expensive