Tweet
Trying to get to the bottom of an ultra lean (20+) running Zetec ST170 on throttle bodies; I invested in a cheap smoke leak finder machine. Considering it was £50 from eBay I was dubious, but actually throws out loads of smoke.
Lean issue: to achieve an afr for 15 to 16, I need to trick the computer with an engine displacement of 3.5L (rather than 2.0L) and smaller injector cc (stay open longer); unfortunately this give an idle of 1400 to 1800 rpm!!!!
Smoke test indicated the redundant idle control vents were letting in a load of air, so taped over those. Continuing to test each throttle body in turn showed leakage around the AIR SIDE trumpets, but zero once past the vanes. I need to re test as this is odd: where could the air be getting in to cause such lean running, so lean that when I press the accelerator (opens vanes) it nearly stalls until the computer responds to the throttle position reading and chucks more fuel in.
Some googling on lean running is not helping.
Lean issue: to achieve an afr for 15 to 16, I need to trick the computer with an engine displacement of 3.5L (rather than 2.0L) and smaller injector cc (stay open longer); unfortunately this give an idle of 1400 to 1800 rpm!!!!
Smoke test indicated the redundant idle control vents were letting in a load of air, so taped over those. Continuing to test each throttle body in turn showed leakage around the AIR SIDE trumpets, but zero once past the vanes. I need to re test as this is odd: where could the air be getting in to cause such lean running, so lean that when I press the accelerator (opens vanes) it nearly stalls until the computer responds to the throttle position reading and chucks more fuel in.
Some googling on lean running is not helping.