So I have a 92 STX extended cab 4x4 4.0 5 speed 160k miles. It has been acting like a toddler who doesn’t get their way. I pulled the codes today and got myself a list of codes that point to a general problem but not sure what the cause(s) are. Codes are 113,157,172,212,452. All codes lead to motor running lean I’m assuming that is why it has been feeling under powered and running rough, not necessarily missing just not a smooth sounding motor. Can anybody help give me a place to start and how to start testing components? ACT/IAT, MAF, 02, SPOUT SYSTEM Thank you in advance

 

You should list the code definitions with the codes since I assume you looked them up, no one knows them all by heart, lol.

Also never "google" a code number, look up any code on a Full List, like this one: https://therangerstation.com/tech_li...gitcodes.shtml
Reason is you need to see what codes the computer could choose from, so what it did NOT PICK, can help you diagnose what it did pick

113 IAT sensor is/was high or open - IAT
157 Mass Air Flow signal is/was low or grounded - MAF
172 Oxygen sensor not switching - system is or was lean - Single, Right or Rear HO2S - Fuel control
212 Ignition TACH signal was erratic (module/wiring) or SPOUT circuit fault - Ignition Systems
452 Vehicle Speed Sensor (VSS) problem

They all have the electrical system in common
Check battery voltage
12.8v is new battery
12.3v is 5 year old battery, time to shop for battery sale
12.2v or lower is failed battery

Engine running battery voltage
14.5-14.9v after startup
13.5-13.9v idling, after 10 minutes of running

I would test electrical system first, clean battery terminals and cables, then clear codes and see what comes back

IAT, MAF, AND..............ECT, TPS sensors all share 5 volt power from computer, so without ECT or TPS codes that shouldn't be the issue

You can test voltage at IATs 2 wires using sewing pins to pierce the wires, should be 3volts key on cold, same for ECT sensor

MAF has Tan and Blue sensor wires, test the same way but engine should be idling, .8-1.5volts is expected

Do you have a tachometer in the dash?
Was it working?

 

I pulled spark plugs and found they were beyond fouled. Truck is running better after changing them out. But I have discovered that I can disconnect the maf and there is 0% difference in motor performance, not sure how this can be considering the importance of the maf. But I currently lifted the truck and put 33-10.50-15s on it and i can roast them with ease. This truck has been a mind blowing ex




perience

 

Yes, bad spark plugs, lol

MAF is not all that important, it is needed so computer can fine tune air:fuel mix

Gasoline has air:fuel ratio of 14.7 to 1, this is a WEIGHT RATIO!!!!!!!, not volume

So 14.7 pounds of air to 1 pound of gasoline
14.7 grams of air to 1 gram of gasoline
WEIGHT

MAF sensors job is to "weigh" the air that's coming in

"hot air rises" why?, because it is Lighter than colder air, colder air is heavier
As you get higher above sea level, elevation, air gets thinner, so lighter

Your engine computer already knows its running a 4 LITER engine, so it will pull in 4 liters of air at wide open throttle every 2 RPMs
It knows how much a liter of air should weigh at sea level at 65degF
So its just math, which is what computers do, math

But you are not always at sea level and its not always 65deg outside, lol.,
So you have a MAF sensor

Engine should run without MAF sensor, but depending on temp and your location it won't run as well without it