backfire = bad O2 sensors? long

shelby2 · 04-02-2001, 07:54 PM

mine would backfire in mine under part throttle, but only some of the time. i know it is from it running rich. i have long tube headers with the o2 sensors welded in and causes the sensors to read lean because the cannot sample enought of the gases. even tried changing the fuel pressure from 30 to 45 with the vacuum disconnected. when i disconnected the o2 sensor harness it did not backfire at all, but would surge and die at stops. i guess that is because it goes to the stock tables for fuel and doesn't look at the current mixture. i am having a chip burned from JMS and should be here later this week. they claim that they can fix the lean condition caused by the longtubes. i also replaced one o2 sensor, and couldn't replace the other because the harness melted on the header, and it didn't make a difference.

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shawn hill
1967 ford mustang coupe, red w/white stripes, hood scoop, front and rear spoiler, sefi and c4, trickflow intake, 70mm mac tb/egr, billet fpr, 24# inj, c&l maf, heavy duty c4 w/transgo shiftkit, msd 6a box w/tfi blaster coil, flowtech longtubes w/turbo mufflers, t-rex inline pump, ported and polished E7TE heads w/1.94,1.60 valves, lunati 292 cam, harland sharp 1.6 rollers, conventional 8" with 2.79 gears (soon will be gone)

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04-02-2001, 07:54 PM	#1
shelby2 Registered Member Join Date: Nov 1999 Location: O Fallon, IL Posts: 87	mine would backfire in mine under part throttle, but only some of the time. i know it is from it running rich. i have long tube headers with the o2 sensors welded in and causes the sensors to read lean because the cannot sample enought of the gases. even tried changing the fuel pressure from 30 to 45 with the vacuum disconnected. when i disconnected the o2 sensor harness it did not backfire at all, but would surge and die at stops. i guess that is because it goes to the stock tables for fuel and doesn't look at the current mixture. i am having a chip burned from JMS and should be here later this week. they claim that they can fix the lean condition caused by the longtubes. i also replaced one o2 sensor, and couldn't replace the other because the harness melted on the header, and it didn't make a difference. ------------------ shawn hill 1967 ford mustang coupe, red w/white stripes, hood scoop, front and rear spoiler, sefi and c4, trickflow intake, 70mm mac tb/egr, billet fpr, 24# inj, c&l maf, heavy duty c4 w/transgo shiftkit, msd 6a box w/tfi blaster coil, flowtech longtubes w/turbo mufflers, t-rex inline pump, ported and polished E7TE heads w/1.94,1.60 valves, lunati 292 cam, harland sharp 1.6 rollers, conventional 8" with 2.79 gears (soon will be gone)