93 xlt 4.0

[eric27]

im getting codes 118 and 412. also every now-and-then the hard fault 998 and a 159. the maf is the 2nd one brand new. i have 3 iac's that i have interchanged with no inprovement. my brake booster is leaking between the booster and master cylinder....my problem is.....maf unplugged, 11mpg with ok preformance. maf plugged in,thick black smoke,and about 9mpg, rpms erratic, sometimes stalls at lights or stops. putts, sputters and often backfires. also with WOT it just boggs down with noooo power like theres no pressure. but the pressure is fine. new fuel delivery sys from the fuel rail to the pump. new fpr also. thaks for the replies......

 

[MrShorty]

My experience is that the KOER 412 is not very useful. It merely indicates that the engine was running rough, which you already knew.

Is the 118 a KOEO code or a CM code? My code list indicates that it is an ECT code, but it isn't the usual KOEO 116 that is normally output when the KOEO test is performed on a cold engine. I would probably pursue the 118 code until you figure out what is causing it, and see if that resolves the issue.

 

[eric27]

youre right the 118 is an ect code. and thanks for the info about the 412. i replaced the brake booster to see if the small vac leak would solve the problem. unfortunantly it didnt do anything but cost me. would a faulty iac cause major driveability problems and horrible mpg? also two things i noticed today was back pressure from the brake booster after the install. i reset the computer and drove it to let it adjust. then after shutting it off i was going to check the booster tube ends(double checking). and when i pulled the end from the booster air came out as if a tire was deflated?..........then rechecking my sensors with my volt meter i noticed only .65 volts to both the maf and iac....is that normal???? thks for the knowledge