Ly-mo
New Member
- Joined
- Apr 7, 2014
- Messages
- 54
X2 on Wheelhorses comments. Your description says 'loaded' for the test phases where you failed- I'll take that to mean elevated rpm and engine load. If the throttle is open at all, then your mixture screws will not affect your CO numbers- only jetting. I think you'll HAVE to jet you carb down a few sizes to pass loaded CO.
Regarding the idle HC failure- the most common misfire that happens at idle and not at high speed is a vacuum leak or idle screws set too lean. I'd start there, then with plugs and wires for good measure. Make sure you base timing is correct and that you vacuum advance is connected properly (port vacuum) and functional.
Another thing, I'm guessing this truck has a catalytic converter- cats need to be HOT to work efficiently. If possible, run that truck hard up and down the highway for half an hour or so before you take it back in to the test station. Minimize idle time before it goes onto the rolls.
Good luck with this. I promise it is possible to have a bronco that runs right AND passes the test- it just takes a little tuning.
Regarding the idle HC failure- the most common misfire that happens at idle and not at high speed is a vacuum leak or idle screws set too lean. I'd start there, then with plugs and wires for good measure. Make sure you base timing is correct and that you vacuum advance is connected properly (port vacuum) and functional.
Another thing, I'm guessing this truck has a catalytic converter- cats need to be HOT to work efficiently. If possible, run that truck hard up and down the highway for half an hour or so before you take it back in to the test station. Minimize idle time before it goes onto the rolls.
Good luck with this. I promise it is possible to have a bronco that runs right AND passes the test- it just takes a little tuning.