Starting roughly just before I garaged the car last year, I was getting a really aggressive sputter and this bucking in the car at about 4,500rpm. It was just before the car was stored for the winter so I couldn't really do much about it. Anyways, I now have the car out since the weather has been nice and for the past month I've been trying to combat this issue.
I don't really know whether I should call it a misfire or not, because I don't want to mislead anyone on what my issue is. I can rev the engine all the way to 6,000rpm no problem in neutral. When I'm in first, the stuttering occasionally happens at about 5,500rpm. The real bad bucking starts at the top of 2nd which is about 4,500-5,000rpm and in 3rd starts as soon as 4,000rpm. I should add this issue only persists when the engine is at operating temp/just above operating temp. If the engine is underneath that center line to any degree, the car doesn't seem to buck and sputter. As much as I hated doing it, I was able to rev the engine right out to 5,800rpm when it was "cold" and it pulled straight through with zero hesitation.
I have replaced the cap, rotor, coil, plugs and wires. I gapped my plugs at .052" and that seemed to be terrible for blow out so I gapped down to .035" and that seemed to make it a little better. I am also running 14 degrees base timing but the problem has been the same whether I was at 10, 12 or 14. I also have a new Motorcraft TFI module I purchased from my local Ford dealership, the 5.0 manual transmission one.
My car is an '86 but previous owner did convert to MAF so I put a BBK fender well CAI which I felt was better than the previous "hot air intake". I also know the car has an upgraded fuel pump that previous owner purchased from the Ford part catalog decades ago so I don't even know the flow rate of it, I can assume more than stock.
I hope someone will be able to help me out with this as its driving me nuts and I want to be able to drive my car how I want without fear of blowing it up LOL. Let me know if you guys might need any more information. Thanks in advance
EDIT: Previously mentioned new TFI module is not installed on the car, just meant to say I have it on hand if install would be a good idea.
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