Having an issue guys! I've got a 2002 4.0 V6 4X4 and for the last month or so I've noticed when driving that the truck seems to surges from time to time and that the idle when first started isn't great especially when it's cold out but it was so minor at first I thought maybe I was imagining it or it was just do to cold weather! The other day when leaving work at night so it was cold out, I went to start it and it started but stalled out right away, I then had to crank it for around 3-4 seconds before it finally started up and ran but with a vary noticeable bad idle worse then it had ever done before, the tach is obviously moving up and down now and you can hear the engine doing the same. I've messaged Ron D and he suggested cleaning the MAF sensor and the IAC valve which I plan to do tomorrow, I've also had a coworker suggest I have a bad TPS sensor. The only code I'm getting is a PO442 which is a small EVAP leak that I've know about and am having trouble locating, has to be a hose somewhere. The idle issue does seem vary much like a fuel problem to me but I wanted to see what you guys think, I did install a new fuel pump last September but not a Motorcraft like I should have but my understanding is that when a fuel pump goes it just stops working altogether. The idle does seem to go back to normal after the engine is warmed up. Any thoughts on what else to check out? Thanks in advance

 

Yep, I'd work these items one at a time:
~ clean MAFSensor; drive & see if that helps.
~ remove+clean+lube+reinstall IACValve; drive & see if that helps; with Engine Idling+Warm unplug IACValve; rpms should drop, if not a vac leak.
~ Engine OFF & Key ON, TPS signal voltage should vary smoothly as you rotate ThrottleBody; if eratic replace TPS.
If PCVValve hasn't been changed in last 33kMiles, do that; inspect PCVValve Hose+Tube assembly for cracks+leaks.
How old are Plugs+Wires & OxSensors; those need replacing every 100kMiles?
Tank of PremiumGas + bottle of InjectorCleaner once\twice a year can help.

 

Thanks Dillard000! I'm going to do the MAF senor and IAC valve today plus I already have a bottle of fuel injector cleaner standing by.
I really don't know if the PVC valve has been replaced or not, I got the truck just over two years ago when it had 123 thousand on it and now it has 134 thousand, but I've never done it myself but will take a look. I did the plugs and wires at the beginning of 2020, so I don't think that's the issue. No codes for any oxygen sensors and I have replaced one sense I've had it, not sure how old the others are but I don't really want to buy new ones unless I have codes showing for them, are you suggesting they can still affect the idle even if not showing codes?

 

Do you have any OBD2 TroubleCodes at this point?

Best renew PCVValve every 33kMiles or at least clean+check;
on LeftValveCover rear; 1/4Turn LeftyLoosy\RightyTighty, gently as plastic tabs easily break;
also inspect PCVValve VacHose+Tube assembly; notorious for cracks+leaks & causing TroubleCodes;
recommend replacing those cheap\thin RubberElbows with tougher 5/8"CoolantHoseElbows.
bad PCVValve\Hose can cause higher CrankCase pressure & oil leaks. Useless PCVValveCoolantLoop may be deleted if desired.
PCVValve with CoolantOxBow is MotorCraft# ev268, without OxBow is # ev243.

OxSensors likely not your immediate problem; they wear over time\miles & reduce MPGs;
best to renew every 100kMiles along with Plugs+Wires; MotorCraft\Bosch recommended;
Bosch 15719 with 24i00 0m610 Long Cable+Plug replaces any Ford 4WireNarrowBand Sensor.

 

No codes showing for the Oxygen sensors, but I am planning on changing the PCV valve as they aren't expensive anyway, I'll check the hoses out good when doing this. I cleaned the MAF sensor and changed the IAC valve as well as cleaned out the throttle body and the idle does seem a lot better for now but the issue wasn't an all the time thing so time will tell!