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05-21-2011, 07:49 PM #1
engine management at WOT -- lean or rich?
Background story: I'm diagnosing a lack of power at WOT and high RPM.
I first hooked up a fuel pressure gauge, rigged it so I could watch it while driving, and took it out. Fuel pressure never dropped below ~60 psi, and seemed steady there. Never seemed to drop off like it would if the fuel system wasn't keeping up.
Hooked up my scanner and rigged it to monitor TPS, MAF, MAP, and O2 sensor. MAP reading did not indicate a clogged cat/exhaust. TPS seemed normal throughout it's range. MAF seemed normal (I cleaned it just for good measure).
Which brings us to the O2 sensor. Both O2 signals looked normal at part throttle (consistently cycling from lean-rich-lean-rich). At full throttle, the O2 sensors both dropped to near 0 V, indicating a lean mix. Some allege that the PCM ignores the O2 signal at WOT, but I thought in those cases it would run rich rather than lean. Does anyone know which it should be? If it should be reading rich/normal/"not lean" at WOT, then it indicates that something (maybe dirty injectors) is still preventing adequate fuel flow into the engine at WOT. For good measure, I put some fuel injector cleaner in the tank, and we'll see if anything changes. If someone knows, I'd appreciate an answer to the question of what the PCM tries to do with the A/F mix at WOT.'98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
'92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
"My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World
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