Rosugh idle on cold start up, reduced power for about 2 minutes

[aliasjerk]

Long story short, I bought a 1994 Ford Ranger XLT 2WD 2.3L 5 Speed off of a friend as a non-runner.

After a Fuel pump replacement, new fuel lines, fuel filter and running a new power lead from the inertia switch over to the fuel pump, the truck starts and runs somewhat normally.

However, I have a strange low power/idle issue after cold start for about 2-3 minutes.

I can start the truck, it will fire to life and run smoothly, I can even take off and drive normally for about a minute, then it will start to sputter, have little to no power and surge/buck pretty badly, after about 3 minutes everything will smooth out and I can drive the truck all day without any issues. If I shut down and start it back up, it will still run fine, but if the truck sits for an hour+ I have to go through the above process all over again.

I did the KOER test and encountered error codes below;

172 - Oxygen sensor not switching – system is or was lean – Single, Right or Rear HO2S – Fuel control

337 - EGR feedback signal is/was was high – EVR

412 - Idle speed system not controlling idle properly (generally idle too low) – ISC

I pulled the IAC valve and found that it is working, also it can adjust the idle if the a/c is running, but I cleaned it for good measure.

the oxygen sensor is a possible fault, but it can read that the system is lean, so im putting that at the bottom of the list until I troubleshoot the EGR issue (which could be related to running lean).

Simply put, I really just want to get the truck so it runs normally at cold start, so I don't have to wait 3-4 minutes to be able to drive it, any thoughts from anybody?

 

[tomw]

EGR should not kick in when the engine is cold, and definitely not when the engine is at idle rpm.
Things that affect cold running, besides general tune up/maintenance items are the ECT, ACT, fuel pressure, timing, and the 'stove'.

If the plugs, wires, and whatever is used to run them are in good shape, functional, then look at the Engine Coolant Temperature and Air Charge Temperature sensor, along with the little vacuum switch/valve that directs heated air to the intake(from the metal 'stove' around the exhaust manifold) when needed. When the valve opens, vacuum goes away, and cool air is fed in. If it is not working, cold weather would make the engine a bit unstable at first start.
If the IAC is working, you will get an over 1k rpm cold idle that will step down as the engine warms. The sensors noted above will tell the computer to add more fuel when cold, coolant &/or air, and once temperature is reached use the O2 sensors(also warmed up) to regulate fuel:air ratio. They also indicate the need for a bumped-up idle speed, regulated by the ECM, performed by the IAC.
tom