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I'm Mike from Orlando. I started off working on cars with my first, 1973 Buick Opel. Points, timing, brake caliper rebuild pitted. I prefer Fords but can work on anything. I just do my car. I'm cheap and prefer to learn and use the books from Ford to make repairs. I went to college for EE but dropped out in 3rd year. If I can take it apart I can fix it. If I cant take it apart, saw it in half to determine issue and replace it. I love learning about STFT and LTFT and knowing what all the numbers mean. That PCM does one hell of a job to keep us off the side of the road.
I currently have a 2007 Ford Five Hundred with 198K. SEL FWD 3.0 Duratec. I do all my own maintenance, troubleshooting and repairs. I've replaced shocks and struts, control arms, brake pads, all fluids, water pump, plugs, COP, pro at removing upper and lower intake manifold(40 min to remove). EGR. Belt and tensioner, only thing I don't have is a cherry picker, prob a good thing since I only have 1 car. soon to have 3 cars when the kids get older.
I'm currently troubleshooting a rich condition, -3 for STFT and 0 for LTFT, B1and B2 O2 sensors 2 voltage is .75. supposed to be .45 therefore rich. - 3.0 STFT tells me its subtracting fuel due to running rich. B2S2 O2 was stuck at 0.0, replaced(I actually swapped B1S2 with B2S2 and the 0.0v followed the O2 sensor). Did smoke test and found leak out of back of the EGR, replaced it. Fuel pressure is 40psi. Still has slight rough idle and stumbles sometimes and B1and B2 O2 S2 both at .75 meaning rich. STFT and LTFT is not very constant. I realize STFT goes up and down and LTFT is supposed to be at or near 0. Those O2 on B1 and B2 sensors 2 scratching my head. I'm thinking fuel injectors but I don't smell and fuel. Probably going to do another smoke test(homemade smoke machine).
hi mike. are you reading sensor 2 downsream values after the cat? they should be mostly steady anyway with slow fluctuations, not following upstreams too closely.do some snap throttles then pull a vacuum line to see how well they respond at both extremes. -3 trims are not bad. stumbling problem may be not fuel related.
Hey Mike, welcome to the forum.
I wouldn't try to (and honestly probably couldn't) find the reason for -3% STFT with 0% LTFT.
That's virtually perfect.
You want the downstream sensors to hang around 0.7-0.8v fully warmed up @ idle. That indicates the cats are storing oxygen.
