Idle cycling & low load stumbling SOLVED!!!!

[Strgzr]

Symptoms:
After air filter change, at load 1500 RPM with soft pedal touch, symptom indicated an ingnition hesitation.

Changed:
Throttle Postion Sensor
Air Idle Control Valve
Fuel Filter
NOT FIXED .

Went to ROWE Ford and performed 90.00 Diagnostic.

Found Driver upstream O2 sensor reporting lean condition causing increase fuel dump in those three cylindars. Noticed increased carbon on tail pipe. Had technicians replace O2 sensor. SMOOOOOTH!!!!

No payment on the truck so I will take the $265 bill. Next Time I will know...

Strgzr

 

[Strgzr]

BTW... 99 XLT 4x4

 

[Strgzr]

Oh yeah.

I did have Autozone scan the truck.

P1150 "Lack of Ho2S21 Switch - Adaptive Fuel At Limit"
P1151 "Lack of Ho2S21 Switch - Sensor indicates Lean"

Guess I reset the code too quick. Should have paid this more attention than I did. Kept thinking ignition/vacuum leak and other stuff. Well, hope this helps others... Strgzr

 

[AlaskanJack]

our 01 sport has been stumbling on start up but once warm all is well. Keeps getting a check engine light and when we take it in the warranty mech says bank 1-2 rich lean. cleans the MAF and all is well for a few weeks then back to same thing.

 

[bigtime57]

rough idle gone!!

i had the same problem but after replacing intake o rings and cam tensioner. . .problem gone and no more bank 1&2 lean errors . . . . .. OOM12 RECALL if you have less than 72K on your SOHC . . . taking for granite you have a SOHC. . if you are over the milage the kit cost me 45 bucks from ford and took a pretty good evenings work but not to bad. .

 

[AlaskanJack]

oh now thats nice to hear...... when we bought it with 75k miles it was doing the same thing from time to time but wife never got around to taking it in for warranty work

 

[Strgzr]

One other thought

I noted that the sumbling only ocurred after the X warmed up. I guess it runs in a closed loop when warming up where by the sensors (in this case the O2) is not taken into account until after the engine is up to temp.

Regards,
Strgzr

 

[racebronco2]

the computer runs in open loop before it warms up .... then in closed loop it uses the sensors

 

[Strgzr]

Picked up a Actron Super autoscanner today. Pretty cool to monitor sensor values. Next time maybe I can save some money...