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FORSFED · 10-23-2003

Well, here's something for all of you to ponder over.

I've had the high rpm misfire problem for some time and some of you know what I'm talking about and have helped me along the way. With a virtually stock (only a 2.5" exhaust) 91 Talon I was getting a consistant misfire from 4500+ rpm's. A week ago I reconnected two vacuum lines which helped at first, but the problem gradually came back.

Tonight I installed a Walbro 255 pump thinking that I wasn't getting the volume of fuel necessary at high rpms. So after installing it and driving, the problem was actually amplified from before. I did some checking on the logger again and trims were at 119, 119, and 104, no knock, 18 deg timing, and 89% duty cylce. Now I don't know exactly, but from my knowledge this sounded awfully high for being stock. So I installed a friends SAFC and tried leaning the car out a lot on the high rpms. From 3k to 7k I went from -5%, -14%, -20%, -22%, and -18%. After one run, the car pulled to redline like the day it drove off of the lot. The DC is now down to 75% and Base FP used to be at 36psi and is now at 41psi. It seems as though it was getting way too much fuel (even before the larger pump) causing the misfires, but I don't know how this could be considering I replaced everything and nothing fixed the problem. Any ideas? I can run the car like it is since everything seems to be in spec, but for a stock car I can't see what would cause it needing to be leaned out so much in order to run properly...

10-23-2003	#1
FORSFED Join Date: Oct 2003 Location: White Bear Lake Posts: 109	Well, here's something for all of you to ponder over. I've had the high rpm misfire problem for some time and some of you know what I'm talking about and have helped me along the way. With a virtually stock (only a 2.5" exhaust) 91 Talon I was getting a consistant misfire from 4500+ rpm's. A week ago I reconnected two vacuum lines which helped at first, but the problem gradually came back. Tonight I installed a Walbro 255 pump thinking that I wasn't getting the volume of fuel necessary at high rpms. So after installing it and driving, the problem was actually amplified from before. I did some checking on the logger again and trims were at 119, 119, and 104, no knock, 18 deg timing, and 89% duty cylce. Now I don't know exactly, but from my knowledge this sounded awfully high for being stock. So I installed a friends SAFC and tried leaning the car out a lot on the high rpms. From 3k to 7k I went from -5%, -14%, -20%, -22%, and -18%. After one run, the car pulled to redline like the day it drove off of the lot. The DC is now down to 75% and Base FP used to be at 36psi and is now at 41psi. It seems as though it was getting way too much fuel (even before the larger pump) causing the misfires, but I don't know how this could be considering I replaced everything and nothing fixed the problem. Any ideas? I can run the car like it is since everything seems to be in spec, but for a stock car I can't see what would cause it needing to be leaned out so much in order to run properly...