confused / check engine on 1999 Isuzu Rodeo

1999 V6 4X4 rodeo with 150,000 miles , never had any trouble until now , low fuel pressure ( lean ) O2 sensors . had fuel pump replaced , Twice ( 35 lbs pressure at idle . O2 sensors replaced . still shows , lean , O2 sensor ( check engine still on ) $1200.00 later . any suggestions on how to fix ? at idle the regulated fuel pressur is 35 , pull the vacume line off the regulator and the pressure increases to 48 - 52 . and the shop I had do the work , pulled the codes , I don't think they have the full diagnostic equip . / they pulled a code of lean / low fuel pressure , changed the pump , same code , changed it again , then O2 sensors , looked for vacume leaks . and give it back , and are stumped

by in Phoenix, AZ on April 26, 2011
2 answers 2 comments
ANSWER by on April 26, 2011
171,174 codes could be vacuum leaks, mass air flow reading incorrectly, pcv vale or low fuel pressure. did you have a real diag or just a code pull with a guess?? i would have a shop ok at it to confirm. as far as the low pressure, did you have the regulator checked?? Thanks for using repairpal. Roy
COMMENT by on April 26, 2011
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COMMENT by on April 26, 2011
you need a new shop. there is no code for low fuel pressure. o2 sensors were not the problem at all. i think they missed the boat with this issue. use the driectory tab at the top to find a shop in your area. you need this checked properly with a shop that will diag it properly and give you an accurate bid for repairs that will fix your car. Roy
ANSWER by on May 14, 2015
I recently bought my wife a '99 Rodeo, 4x4, V6 3.2L with 250,000 on it. Car is in extremely good shape for it's age and mileage. Problems encountered are very similar to yours right down to the fuel pressure readings. What I've managed to determine so far: Replaced PCV valve & gromment, air filter, fuel filter, valve cover seals,(leaking oil) #3 cyl compression low(stuck compression rings), replaced fuel rail(injectors and all)with a boneyard assembly from 2002 model, replaced fuel injector regulator(which cured engine surge). Still has low fuel pressure. I don't worry about the MIL light as it's a secondary indicator in this case. After doing my homework, it comes down to replacing the fuel pump/sending unit assembly, which should cure the "check engine light". Thanks for posting your car prob.
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