Running great for a while then suddenly throttle response issues!
Bought my system a while back from a friend and had it running smoothly with little issue for a good while. Recently however i have been experiencing severe bogging, hesitation and "carb" backfire when trying to accelerate more aggressively. I have changed out the efi rated filter to rule out a clog (which has been an issue in the past), I have played with the IAC steps and will get it to register between 3 and 10. When I go to accelerate aggressively, the engine bogs down and the AFR climbs then when the engine starts to even out the afr drops before returning to normal, I have attempted to remedy the issue by adding to the accel pump as seen on forums and in tech videos but nothing seems to help. It was a very dependable unit for quite some time. When i attempt to drive it more mildly it bogs and does not want to accelerate as if it has a fuel delivery issue. It turned my 73 f250 with a 360 into a very dependable vehicle and was a milestone in my restoration. Any ideas?
Going to be a difficult issue to diagnose. Back firing through the carb is more of a timing issue.
You should consider contacting FITech & getting updated software & install. This way you are starting fresh with settings.
Fuel filters. Years ago I was running a 100 micron pre-filter & 10 micron post-filter with my inline fuel pump. These were the cheaper "stainless steel screen" filters. When the fuel heated up - the screen would expand - restricting fuel. Engine would would run poorly & die. I replaced the filters with high quality cartridge filters - never had an issue since.
Quote from CF95 on June 11, 2025, 9:26 pmBought my system a while back from a friend and had it running smoothly with little issue for a good while. Recently however i have been experiencing severe bogging, hesitation and "carb" backfire when trying to accelerate more aggressively. I have changed out the efi rated filter to rule out a clog (which has been an issue in the past), I have played with the IAC steps and will get it to register between 3 and 10. When I go to accelerate aggressively, the engine bogs down and the AFR climbs then when the engine starts to even out the afr drops before returning to normal, I have attempted to remedy the issue by adding to the accel pump as seen on forums and in tech videos but nothing seems to help. It was a very dependable unit for quite some time. When i attempt to drive it more mildly it bogs and does not want to accelerate as if it has a fuel delivery issue. It turned my 73 f250 with a 360 into a very dependable vehicle and was a milestone in my restoration. Any ideas?
Quick question: Is the bogging happening when hard accelerating from a complete stop? Also is it happening while you are driving and you let off the gas pedal and coast and then you hard press the pedal to accelerating again? Also what model are you running? Are you using the fitech to control timing? Have you check to trouble codes on the handheld? Is the fuel pump inline or in-tank and what brand is the pump you are using? I also recommend Walbro branded pumps.
Fuel command center pump after the mechanical fuel pump. It Boggs on a more aggressive pedal from a stop, gotta very lightly accelerate to keep her going. I haven't looked into timing as also mentioned I will give that a try, would the backfire through the carb be too advanced or retarded?
if you have the first gen ( round and silver in color), they were notoriously problematic. You may want to think of changing it. But try this first. On your hand held go to GO EFI Tuning and select Fuel Cut Control. Once you are there select DFCO Enable Temp and set it to 300 and save. Make sure to turn key off after saving. That will stop the fuel pump from shutting off. Basically to save fuel the computer will shut off the pump when decelerating or at a stop and turn on when you go back to the pedal causing a lean mode due to lack of fuel or the delay for the pump to come on..
So after trying to do some tuning and adjustments I started to recognize that once i made a tuning change and shut the truck off to save it, i would start it back up and it would run like a top, getting me through a few stop signs before the symptoms would start again, no aggressive accel and no holding it open like at all. I would have to lightly touch the gas to keep the AFR from spiking. each time i would try to accelerate the AFR would jump to 20+ and if i did so more aggressively she would nearly lean out and die. i have the fuel cut off moved to 300 as advised and the AFR at idle fluctuates but is fairly consistently between 3-10. I keep increasing the accel pump settings but the issues remain. the Fuel command center typically keeps pressure between the 40-60 marks on the regulator. She was running great for a good while now i feel like shes fighting to stay off the road! lol
Look at the fuel pump in the fuel commander and see the condition of of the filter for the EFI pump in the fuel commander. Some times they come off or deteriorate. You may also want to start from a clean slate, such as setting it up like it was new. What I dont like is your varying pressure of 40-60 lbs. On my car it is rock solid pressure, but I am running a new EFI gas tank with a Walbro intank pump and have had no issues since 2017. Your mechanical fuel pump or the feed from the gas tank may be causing the varying fuel pressure.If you dont have anyone in your area that can help you, you may want to consider sending the unit to FiTech and see if the EFI unit is good and there are no-issues. At least you can rule that out. Personally I would get rid of the fuel commander and ether get a tank with a intank pump , or a newer version of the fuel commander, or get a inline EFI pump. I was helping a guy with his unit and we tried everything to get it running good and in the end, it was a intermittent faulty performance distributor made in China, and we swapped it out with a GM distributor and he has had no issues ever since. Call fitech support and mention you have that varying fuel pressure with the fuel commander. They will at least let you know that is normal or problematic. If I was close to where you live, I would be more than happy to help you.