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Re: 1996 es300 trouble code po172 and misfireing on all...
Whats going on here is that you have a too rich fuel air mixture. This will cause your misfiring and set off the PO172 Code. Your Bank 1 O2 Sensor is picking up the too rich mixture. This O2 sensor is location on the #1 Cylinder side (so you problem could be in #1/#3/#5 Cylinder). A dirty MAF Sensor, loose plug wire, dirty/broken spark plug, dirty fuel injectors, vacuum leak, and PCV Valve could all be a cause. I would run some injector cleaner through and also clean the MAF Sensor, change your PCV Valve. This would be an easy and cheap start for you. Good luck and thanks for using FixYa!
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codes p 0300 through refer to misfires on each cylinder with the end number ( 301 is no 1 cylinder , 302 is no 2 cylinder ans so on)=== causes --engine mechanical fault , ---wiring---ignition/ fuel ---injector/s---ECT/ MAF sensor/s ---ECM
most misfires are from injector faults like dirty/blocked tips, low fuel pressure , no pulse or problem pulse from ECM rather than plugs and wires and coils
codes p0171 refers to system to lean bank 1===causes ---intake exhaust leak---air system---maf/vaf sensors ---fuel pressure / pump---injectors ---heated oxygen sensor ( HO2S)
code p 0172 is system to rich-====causes ---intake blocked ---EVAP cannister purge valve ---fuel pressure --EGR system---injector/s ---HO2S
couple these two codes with the misfire codes , I suggest you look at the injectors, fuel pressure (too low) from EVAP problem not venting tank, fuel pressure regulator, EGR system
Diagnostic Test Code (DTC) P0302 has a generic description of "Cylinder Misfire - Cylinder Number 2".
A misfire simply means that when it came time for that cylinder to fire, it missed its chance.
There are many things that can cause a misfire. Some of the things are listed below. Diagnostics should be performed to eliminate the possible causes so you don't spend a lot of money replacing parts trying to "guess" what is causing it.
p0300 is code for miltible misfires. The p0172 is code for a rich reading from engine bank #1, this code may be set by the misfireing causing raw fuel to exit that bank to the sensor in the exhaust system. The most common cause is spark related, spark plugs, wires, dist. cap. etc. A less common cause is with the fuel injection system.