This truck still has alot of health left in it, but some reason it starts to misfire when I apply lite steady acceleration while moving down the road. No other misfires or hesitations any other time The idle also stumbles around alittle but not to bad.

Planning on pulling my spark plugs and checking them today. They are only a year old, same with the rotorcap and wires.

Im starting to think that its a sensor. Maybe the IAC valve or maybe the TPS is out of range. I checked for vacuum leaks and didnt find anything. Such a simple little problem and I cant figure it out.

Ill also reset the codes and pull them, not sure if i have any new or not.

Anyone else want to take a guess at it?

 

Do you know what the fuel pressure is ? Could be an Ignition Module, Coil. But could also be a sensor. Or something as simple as a ignition switch, What year and model Timok1

 

my bad 91 4.9

 

91 f150 I6 4.9....It only has 103,000 miles so it shouldnt be acting up just yet. Was taken good care of.

Things came up and couldnt pull the plugs or the codes, gonna have to put it off to tomarrow.

The regular ignition swith that the key goes in is acting alittle slugish in the on position, may be in need of alittle oil but cant understand the process that this makes.

I have no equipment to check fuel pressure. Im just hoping it will be the plugs, install a new set of MotorCraft and away we go.

You would think with all the knowlege here on the forums, was hoping someone may of had the same symptom in the pass and got it corrected.

 

A few of us have had the same issue (myself included), but no definite solution yet.

Likely suspects that have cured this for some, improved for others, did nothing for others:
VSS sensor on tranny
RABS sensor on rear diff
TPS sensor on throttle body
Tranny flush/fill
Dr. Tranny Shudder Fix (2oz additive that helps smooth tranny shifts for autos)

I've tried all of these and still have the same issue... Each has made the problem better, but it's still there. I've also heard that the Ignition Control Module could help, but haven't tried that yet.

 

I'm fighting the same issue it seems on my '95 5.8. Yesterday I replaced the plugs, wires, cap, rotor, TPS and fuel pressure regulator. Also, I took throttle body off and cleaned it up, the EGR seemed to be working ok by testing with the vacumn suction test. I was pulling the 172 code before all this, I have cleared codes and going to run tests today. I have no CEL as of yet on my little test drive but the hesitation with light throttle is still there, no matter what speed your at, mash the gas and she runs like a bat out of hell.

 

The O2 code usually comes along when you're overdue for a tune-up, have EGR issues, gummed up intake, improper timing, etc. The O2 sensor is just telling you to figure out what's wrong, and you've probably cured that.

I don't know if anyone has had success with replacing the ICM or not. It's been mentioned a few times, but I've never heard the results.

 

...but if you are shooting the 172 code whats the percentages of the o2 actually being bad since thats all you have to go on? Granted, the other part of the code states lean.

 

I don't the odds, but I replaced my O2 sensor at one point, thinking that I had done everything else that could be triggering the code. The new one kept giving me the same code until I finally figured out the real issue.

 

So what was your issue?