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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xj-s] Re: 4 wire diagnostic connector (XJ-S Digest V2 #205)
David Johnson wrote: > ... > > I found the mixture was VERY lean when in open loop (below 1% CO). The > mixture was OK when in closed loop (about 1 to 2% CO). The voltage in > closed loop was about 2.5V to 3.4V in closed loop, and 1.85V in open loop. > This indicates a lower voltage gives a richer mixture. I guess this is why > jag put the computer in OPEN loop when in park. There are LESS emissions. > This suggests to me that you should NOT disconnect the jumper for the > emissions test. Any comments. > David, in open loop the 02 circuit is disconnected from the rest of the circuits. The 1.85 volts you read was the 02 circuit just 'talking to itself', it has no effect on mixture. However, 1.85 still seems low, I'll check it out next time I work on an ecu . In theory (on the xjs) the open loop mixture should be close to the center of the closed loop swings. If the car is leaner in open loop idle you can adjust the idle CO setting. If it's leaner in open loop at 2500rpm (where the idle CO adjustment has no effect), then your fuel pressure might be a bit low or something else might be making your car run a bit lean... ask Kirby or group for input on that. Don't know if I should include this.. might offend the purists :), but for the sake of completeness here 'this' is. If you need to increase the fuel pressure just ONE OR TWO TENTHS of a bar you can try this on the pressure regulator (driver's side one (US) if you have two): Put a small pulley wrench around the top of the regulator with a socket over the vacuum port (the legs of the wrench grabbing the bottom of the ridge around the regulator). Turn the wrench screw down onto the top of the socket. Turn 1/4 to 1/2 more turns then remove wrench, reconnect vacuum hose and check pressure/feedback voltage. Repeat procedure until the fuel pressure/feedback voltage is where desired. Again, do this only after you have checked out all other possibilities for lean condition. Walter PS Will borrow Kirby's quote on this one: If anything is to be accomplished... References:
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