Stardup / idle issues

[NeXtras]

For a few months now, on a cold start my truck would sometimes dip down below 500 rpms on start up, but only for a few seconds then would shoot up to 1500..

the other day, it wouldnt stay running unless i had my foot on the gas, I replaced the IAC valve so far, stays running, but this morning when i started it i got that low low idle at start up briefly...

i dont know what else it could be... spark plugs? cap and rotor has less than 10k on it.. plugs and plug wires have mayb 75k on them

 

[Skandocious]

Founds like it's dipping during open loop and then resumes regular operation once it reaches closed loop. You can probably track down the problem by comparing the differences between open and closed loop (which sensors are being used, etc).

http://fordfuelinjection.com/?p=4

 

[Skandocious]

Finally found the chart I was looking for. This'll show you which sensors are used in each mode:

 

[Skandocious]

Looking at the chart above I'm thinking either TPS or o2 sensors. Leaning more towards the former. Have you tried pulling the codes?