So this week the rover started to act up again. After sitting all night the rover takes 2 or 3 attempts to start. It will then idle high about 900 to 1000rpm until warmed up. Once warm the truck drives great and has no starting issues even after sitting for over 3 hours. i am also averaging 12-13mpg. could this be fuel pump bleeding pressure or may be a vacuum line issue. I just replaced the idle air control valve and that did'nt change a thing. Pressure on the rail after sitting all night seemed to be close to zero. Any ideas. Im kind of leaning towards fuel pump. Its a 1997 disco 4.0v8

 

Pressure when pump running should be 32-34 PSI, which you can measure. You could have both issues. One way to isolate the fuel pump issues is to turn key to position 2, pump should run a couple of seconds. Turn off, repeat 4 times. If pump is weak this primes the the system up to the pressure. A new IACV may not get "re-learned" by the ECU without a dealer type computer reset of adaptive values. The ECU is always trying to adjust the system based on conditions and wear of parts (like throttle stop, etc.). You might try cleaning old IACV with carb cleaner and try it again.

Vac leaks can also involve the PCV system, and usually that needs to be cleaned out anyway. A little carb cleaner sprayed at suspect areas can change idle rpm at a leak.

 

Thanks buzz

I checked the pressure at 30 psi, I even checked the fuel pressure regulator and it seems to be working. I pulled the fuel temp sensor and cleaned it. the old IACV had the same issue with rough idle. today I ran in to the store for 15min came back to start the truck and ran rough at idle, gave it some gas and it seemed to smooth out. it almost feels like an bad ignition coil? I dont really know at this point. Is there any way to check the ignition?