Psyco-Clone

when the truck is first started, it takes more than 10 seconds to have the ECM reading the O2. The O2 is ignored until the water temp gets to a certain level. The engine runs in “open loop” during this time & the O2 is inactive. Once the ECM goes to “closed loop”, then it starts to read the O2. I would check your MAP, or even check the voltage to a few of the sensors. Did you make sure all the grounds were connected & the paint cleaned off where they connect? On these EFI systems, ground is very important. Check the voltage on the TPS & MAP. You have 3 wires on each. One is ground, one is +5V dc, & the other is the output from the sensor to the ECM. This should read as low as .5 volt up to 5 volts throughout the movement of the sensor, with no dead spots in between. If your ground is poor, then you will not be getting a full 5 volts to the sensor.

Also, if the temp sensor is not working properly, the ECM may think the water temp is higher than it actually is, so the ECM may go into closed loop sooner than it should. This can cause erratic idle quality.