vandior2001 Posted March 11, 2016 Share Posted March 11, 2016 hello This is my first post but i have found a lot of useful info here so thanks guys. I have a 1987 4x4 4.0 I6 mpi that i have been rebuilding for the past few months. i got it running well but now i have had major problems in the last few weeks. When the engines cold it puts to much fuel in, it misses backfires and shudders badly if you push the gas pedal down. the tail pipe smells strongly of fuel. Run it for 15-30 mins and it will run fine. i also get only about 12 mpg right now. I have rebuilt or replaced (with in the last 800- 1000 miles) nearly everything in the truck. engine was fully rebuild as was the transmission and transfer case new injectors, fuel pump, regulator, every sensor except the oil pressure new computer (bendix), Ignition Control Module, coil, plugs, wires, cap, and rotor About the only thing i haven't replaced is the starter and alternator both tested and working fine. i can't find the problem and it's driving me nuts. Thankful for any help or wisdom anyone might have. P.S. i just replaced the temp sensor fyi side note on my mods to the truck Rusty's Trail Bumper 4.5 inch lift ( Rusty's leaf spring pack kit ) 285/65R18 BF Goodrich TKO 2 Anyone know where i can get bigger axles 44's or 60's (what to look under in the junkyard)?? Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 11, 2016 Share Posted March 11, 2016 Replace the O2 sensor? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 11, 2016 Share Posted March 11, 2016 Check the line from the throttle body to MAP sensor. If it leaks vacuum, the Jeep will run pig rich. Link to comment Share on other sites More sharing options...
vandior2001 Posted March 11, 2016 Author Share Posted March 11, 2016 O2 is new also will the fuel resistor on the fender make your fuel pressure low? just replace the fuel pump and getting about 26 psi 34ish with the regulator unhooked Link to comment Share on other sites More sharing options...
vandior2001 Posted March 11, 2016 Author Share Posted March 11, 2016 Check the line from the throttle body to MAP sensor. If it leaks vacuum, the Jeep will run pig rich. know where i can get replacement hoses and elbows?? most are worn but not leaking that i can tell Link to comment Share on other sites More sharing options...
Eagle Posted March 11, 2016 Share Posted March 11, 2016 Check timing and distributor indexing. Link to comment Share on other sites More sharing options...
vandior2001 Posted March 13, 2016 Author Share Posted March 13, 2016 Check timing and distributor indexing. just rechecked it it's dead on is there anything that will make the fuel pump run at a lower PSI just replaced the fuel pump and it's running the same 25ish PSI as the old one Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 13, 2016 Share Posted March 13, 2016 The fuel pressure regulator might be bad. Engine running the pressure gauge should read 31psi w. vacuum, 39psi w/o. Link to comment Share on other sites More sharing options...
vandior2001 Posted March 13, 2016 Author Share Posted March 13, 2016 fuel pressure regulator is new and there is about a 8-10 psi jump when the vacuum line it removed Link to comment Share on other sites More sharing options...
HOrnbrod Posted March 13, 2016 Share Posted March 13, 2016 Try another gauge. Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 13, 2016 Share Posted March 13, 2016 fuel pressure regulator is new and there is about a 8-10 psi jump when the vacuum line it removed Doesn't mean it's good. Fuel filter new? Try another gauge, or another regulator. Link to comment Share on other sites More sharing options...
vandior2001 Posted March 14, 2016 Author Share Posted March 14, 2016 Got fuel pressure where it should be, but still have the missing / backfiring problem when cold. could it be something other then fuel? I double checked the timing it's dead on. just change the plugs (champion copper plus) and cap/rotor/wires have less then 1k miles on them. the problem has gotten progressively worst, so i thinks it's something going bad but i can't think of what. could the Ignition Control Module be the problem? Link to comment Share on other sites More sharing options...
Newton Posted March 15, 2016 Share Posted March 15, 2016 check all compression on cylinders should be between 120-150 psi.. Link to comment Share on other sites More sharing options...
vandior2001 Posted March 28, 2016 Author Share Posted March 28, 2016 problem found!!!! it was the flywheel sensor. the cable was about 2 feet long and fell down near the exhaust pipe, baked off the coating and burned some of the wire. replaced and it runs great! Link to comment Share on other sites More sharing options...
cruiser54 Posted March 28, 2016 Share Posted March 28, 2016 problem found!!!! it was the flywheel sensor. the cable was about 2 feet long and fell down near the exhaust pipe, baked off the coating and burned some of the wire. replaced and it runs great! Link to comment Share on other sites More sharing options...
DirtyComanche Posted March 30, 2016 Share Posted March 30, 2016 Is there a single CPS out there that actually has the wires secured as in the picture? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 30, 2016 Share Posted March 30, 2016 Is there a single CPS out there that actually has the wires secured as in the picture? On the ones that are still running? Link to comment Share on other sites More sharing options...
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