I'm having a moderate to severe driveabilty problem with the engine bucking and hesitating at part throttle cruise. It only occurs when the engine is warm and improves when I disconnect the O2 sensors. I got the car on the road in April (just before the "Deadline") and have had the problem from day-one. I've gone through everything to check for and repair any vacuum leaks.
I'm running a new Ford Racing Boss 302 crate motor and Mass-Flo EFI system with 30lb injectors. I'm not getting any trouble codes.
Has anyone had a similar problem or any thoughts on how to diagnose this?
If your air cleaner is mounted in the fender well above the headers your intake air is too hot on humid days. You can add a 3 1/2" dia. X 18" flex duct between the air cleaner and the Mass-Flo then relocate the air cleaner up front behind the radiator into cooler air. I then wrapped the intake tube with a heat shield blanket. Intake air went from 170 degrees to less than 100 degrees. Problem solved. If you need pictures email or PM me.
Thanks for all the replies. Sorry it took so long for me to respond...family stuff took a priority
I'll try to answer all the questions in one shot:
1. I'm running 40 psi fuel pressure
2. The connectors for the O2 sensors were labeled and the way the harness is designed would make it almost impossible to switch right and left sensor leads.
3. I called Mass-Flo about this problem sometime in May and the Tech Support guy I spoke with said the problem may be due to the ram air effect of the hood scoop causing turbulent flow through the MAF. He suggested I block off the front of the air cleaner to help smooth it out. I did reduce the problem, but didn't completely eliminate it.
turbodon - I hear what your saying...in fact the reason I disconnected the O2 sensors was to force it into open loop to see if the richer fuel settings would cure the problem - made it better, but didn't cure it.
The first thing to check is the fuel mixture. Just like any job, you need to invest a little cash in the right tools. Spend the money and buy an LM-1. Otherwise you're just guessing what your mixture might be.
Second, what's your ignition system like? Too much timing coupled with not enough fuel can do exactly what you're describing. Adding more fuel can improve it, by making it run rich.
Welcome to FFCars! The
representations expressed are the representations and opinions of
the FFCars.com forum members and do not necessarily reflect the
opinions and viewpoints of the site owners, moderators, Factory Five
Racing, Inc. or Ford Motor Company. This website
has been planned and developed by FFCars.com and its forum members
and should not be construed as being endorsed by Factory Five
Racing, Inc. or Ford Motor Company for any
purpose. "FFR", "Factory Five", "Factory Five Racing", and the
Factory Five Racing logo are registered trademarks of Factory Five
Racing, Inc. FFCars.com forum members agree not to
post any copyrighted material unless the copyrighted material is
owned by you. Although we do not and cannot review the messages
posted and are not responsible for the content of any of these
messages, we reserve the right to delete any message for any reason
whatsoever. You remain solely responsible for the content of your
messages, and you agree to indemnify and hold us harmless with
respect to any claim based upon transmission of your message(s).
Thank you for visiting the FFCars.com Forum dedicated to Factory