[xj-s] Re: XJ-S Digest V2 #205

["David Johnson" <davidj@ecentral.com>]

This is one of the best tips in a while, got any more like this? A great
way to test the O2 sensors are working without pulling stuff apart. I
disabled the jumper in the trunk and checked the voltages at the
green/white and green/red  wires (not green / pink) , both voltages / banks
seemed to be in spec (2.5V to 3.5V). I also have a CO meter to plug into
the exhausts. 

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.


Dave Johnson
Two 88 Hess Conv. 
Tag "Pusycat", need a good suggestion for a second tag?


> the 2 wire jumper disables O2 feedback in park and neutral. It's in 
> series with the park/neutral signal from the gear shift lever to the 
> ecu. When you take the car for an emissions test, you need to remove
> this jumper so that the computer can run in closed loop in park (Isn't
> this cheating? :).
> The four wire connector is used to monitor what the ecu is doing
> while in closed loop. This way you can check if the engine is running
> too rich or too lean or maybe one side richer than the other.
> The green/pink wire is the driver's side bank, the green/white is for
> the passenger side. Black is ground.
> In closed loop the voltages should vary up/down between about 2.5 to 3 
> volts. A lower voltage means that the ecu is trying to lean the mixture
> in that bank, or, the mixture is too rich. A high voltage means that the
> bank is lean.
> In practice I would just make sure that the voltage is not constantly
> below 2.2 or constantly above 3.5 ..excuse me a second..watching Brazil
> Holland penalty kicks.....
> 
> Holland is out! Anyway, I would check that the difference between left
> and right bank is not more than ~0.5v . You can set the idle mixture
> with the idle mixture pot on the side of the ecu. Factory setting is
> 6 'clicks' back from full rich +/-1 . Then check at 2500rpm.
> 
> The green/white wire is the power to the ecu.
> 
>

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Follow-Ups:

• Re: [xj-s] Re: XJ-S Digest V2 #205
• From: Mike Morrin <mikem@southern.co.nz>
• [xj-s] Re: 4 wire diagnostic connector (XJ-S Digest V2 #205)
• From: Walter Petermann <corsaro@brokersys.com>

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