MAP question

Hi
I have a 1996 xj cherokee sports, 4L Ho , auto , RHD , stock gears running 30-9.3 x15 tyres. Have just fitted a scangauge 11 for trouble shooting and have noticed that my map readouts seem off , have compared readouts with multimeter MAP has 5.1v going in and earth tests ok, scangauge seems to read in volts , at idle wormed up i am getting 1.9v to 2.1v ,driving at WOT reads 4.4v ,but at 100Kph on flat road it reads 3.2 v to 3.6 witch seems high to me .TPS reads 13 at idle ,74 at WOT ,28-30 at 100Kph.fuel consumption seems high as well 16-18 l/100km ,can anyone give comparisons
cheers
john

IMO, the better gauge to use when chasing poor mileage is an AFR (Air Fuel Ratio) gauge. This gauge uses a wideband O2 Sensor and displays the actual running mixture. 14.7 is the target.

You do not say how may kilometers are on your rig so it is a bit tough to help out. IF, and it is a big if here, the stock O2 Sensor has gone wonky then, the mileage will go right along with it owing to running rich.

The PCM uses the MAP Sensor, the O2 Sensor, the Throttle Position Sensor as well as the Engine Coolant Temperature Sensor to determine the desired air/fuel mixture. The Crankshaft and Cam Position Sensors are utilized to determine the ignition timing.

Out of curiosity, what does the Scangauge report the O2 Sensor voltage is? Should the PCM believe the engine is running lean, it will fatten up the mixture to compensate.

Hi
the jeep has 200 k on the clock , I have owned it for 3 mounths , motor appeares to have been rebuilt . the o2 sensors are reading per cat swings fairly quickly between .25v to .85v sits around.5 to .7v at 100kph post cat sits between .2v and .6v thay appear to be ok, looks like thay were replaced not that long ago. just does not seem to have much responce from 1/4 to 3/4 throttle

TPS reads 13 at idle ,74 at WOT

Click to expand...

i assume the scan tool is showing TPS percentage here....13% at idle and 75% at WOT is off. should be 0% at idle and over 85% at WOT
TPS voltages should be about .5 to .8v at idle and 4.5v or better at WOT

have changed TPS with new one and still have about the same readings ,is there any particular way to fit it