1999XK 4.0LCEL PO171-PO174&P1000 STAY ON

Question

CLEAN AIR MAS SENSOR,CHECK FUEL PRESSURE 40 PSI. W/VAC ON FUEL REG.35PSI WITH VAC.GUN, ENGINE TEMP,190. BEFOR TEST CLEAR CODES START ENGINE THE IDLES ALOT BETTER,RISE RPM UP TO 2500 RPM HELD IT FOR 3 MJN, LET IDLE FOR 4TO5 MJNS, TURN OFF ENGINE      INSTALL VACLINE BACK TO FUEL REG, BUT DID NOT CHECK TO SEE JF I THEIR ANY VAC, CHECK TO SEE IF ANY VAC LEAKING FROM INTAKE MANIFOLD BRAKEBOOSTER,CRANK VENT HOSE NO LEAKS,CHECK OTHER 'VACLINE&HOSE'S CONNECT ALL PARTS THAT WAS REMOVE PARK THE JAGUAR XK. THE NEXT DAY START UP THE AUTO TO PUT 200 PLUS MILES ON ENGINE SINCE I CLEAR THE CEL, START ENGINE THE IDLE RPM BE COME UP AND DOWN THE CEL BACK ON CODE PO171-PO174 P1000.CAN YOU PLEASE TELL ME HOW TO TEST AIR MAS SENSOR,& BANK 1&BANK2  PRIMARY O2 SENSOR?   THANK [email protected]

Answer 1

P0171 and P0174 fuel trim lean codes condition , the fuel pressure is correct , with the idle going up and down , the MAF sensor is not going to do this, nor the 02 sensor, P0171 and P0174 are lean  engine condition, The best way to resolve this is to check the fuel trim. At first start up and the engine idle has a surge on it , the engine needs fuel, at start up if the engine is cold the 02 sensor are ignored until closed loop. or operating temperature,

​ A good operating 02 sensor will have a high and a low reading ,or switch from 250 mv to 750 mv.

​ Fuel trim should be look at you will have a short trim and a long trim one for Bank 1 and the other for Bank 2, Both short and long should add up no more than 10. Here the short and long are equal to 20, The idle is good being a V8 and coolant temperature is good. The problem here was the pressure regulator was stuck open . For a Jaguar  the best way is to get the fuel trim reading from any generic scan tool with live data.