OBD readings

[spanky2000]

Hi, I recently bought an Autel scan tool to try and figure out what was going on with my misbehaving 182. It connects on KWP 2000 and reads about 15 parameters. I have my head around all but three. Would anybody be familiar with why the following happens:
1) Calculated Engine Load reads around 55% at tick over but if I so much as brush off the throttle it goes straight to 100%,
2) Long Term Fuel Trim never varies from -4.7% (I recently replaced the pre-cat o2 sensor and while it shifts around much quicker, and gets much closer to 0.9volts than the old one, there is no difference in long or short term fuel trims),
3) Short Term Fuel Trim on Post Cat o2 Sensor never varies from -100%.
Thanks!

 

[da rok]

engine load is calculated by using the map sensor, can take it out and give it a clean, if you are having idling issues or bogging from cold start this also points to the map sensor... most generic obd readers will only read 1 fuel trim, the other will be max or min, the one it reads should vary by a max of + or - 20% which is the range of what the computer will adjust using the lambda sensor, if the computer thinks that the lambdas are talking kak then itll use the map sensor for fueling... if your pre lambda voltage is going up and down once a second then this is normal fueling, if you want accurate readings and diagnostics the best thing to use is a clip...

 

[spanky2000]

Thanks for that. Also just in case its of benefit to anyone, my ignition advance cylinder 1 reading was jumping all over the place so I cleaned the TDC sensor (over flywheel) and the readings smoothed out. It wasn't particularly dirty but the car is notably steadier at part throttle now. The reason I mention it was because I never knew from driving it that there may have been an issue. It could also have been a bad connection to the sensor. Maybe its no harm to give the sensor a clean now and again and check it's wiring.

 

[da rok]

Tdc sensor has a habit of building up filings and gunk, its good to give all the plugs and sensors a clean every few years