I have a 97 Van with a 5.4L Triton. It started giving a problem past week when engine is cold. After starting it will miss and idle uneven, sometimes the rpm drops to below 400, and even has stalled a few times. In past few days it lacks power. After 1 min it will idle smoother, and put in gear (auto) and it goes 5-10 mph just at idle, but, give it gas and it sputters and almost dies. Baby it and i can get it going - takes a while but can cruise on freeway. After 10-15 min when engine is fully warmed up it runs fine.

Today Chk Light finally came on. P1152 - says it is O2 sensor related - running too rich. I have scan tool (blue tooth and see signal on computer screen), seems like both O2 sensors are switching about the same time between rich and lean fine. So, where else to look for prob?

 

I've had the same issue, but the loppy idle only occurs when humidity is extremely high or it rains. I've noticed this for the past 6 months after I changed my COP's, and I've finally triggered a CEL. I'm curious if I'm right it my hypothesis, or if it's another issue. I'll let you know when I find out; even if this thread is old. I gotta out out some information to help others finally, as I've learned so much from others.

All the best!

 

Shot in the dark. Are you able to view long term fuel trims? If they’re high, you might have insufficient fuel flow. O2 sensors read lean, injectors at high trim, ECU doesn’t have a code for that. I experienced this in a non-Ford. Started and ran fine but occasionally low on power. I forget exactly what O2 sensor codes it set. I threw parts at it but it was a fuel pump that fixed it.

Sixto
07 E350 5.4 173K miles

 

That code actually says there is no oxygen sensor signal available (Bank 2 Sensor 1) which is the driver's side front sensor.

If a OBD0II scanner can view live data including operating temperature of the sensors that's one way to determine if the oxygen sensor is doing its job. As mentioned fuel trims are a helpful metric to know as well, more so while driving than just idling.

I'd dig into this a bit deeper before just throwing parts at it!

 

I had this problem with 2 vans and replaced the idle air control valve. I was not getting any codes. Same symptoms that you described. Both times, the problem was resolved.

 

I've had a few Air idle control valve replacements before; usually I get a fog horn like sound upon cold start ups when that's the issue. Last time I replaced with the Hitachi? If memory serves me right and haven't heard a similar sound since. I will have to get a better scanner to check fuel trims and O2 readings. I haven't because the learning curve, but I'm always dropping motors and working on something so it's probably time. Currently I dropped a WDI short block in my F450, and had UCF rebuild and ring the heads, rebuilt the HUEI injectors completely; and had a start up issue. Long story short in my busy season I didn't have time so I took it to the shop; $3,500.00 later and Im towing my poor baby home.... SMH I should've done it myself! A mechanic that blames someone else working on something because his poor trouble shooting and ability to locate the problem seems rampant now a days... I even told him what he needed to do! He wants me to buy all new Ford injectors ($7,000 installed). No thank you; I'll take it from here.