First Start Low Idle

[enjr44]

Another weird idle problem!! - 2002, 4L, 2WD, auto, about 85K miles. No codes, none. Drives great.

This happens only on the first start of the day. It starts right up (like it always has); but, idles at about 750/800 rpm. Not the “normal” 1500 rpm. If you put it in drive or reverse it holds the 750/800 rpm. If you manually raise the idle to 1500 or 1600 it holds at 1500 (1200 in drive) until the ECU drops it as it warms up. This problem started out being intermittent. Did it sometimes; but, worked normal most of the time. It now has the first start low idle all the time.

Every start after the first start (at least for 4 to 8 hours), it goes to 1500 and holds until the sensors/ECU lowers it to somewhere between 750 and 1100 rpm, depending on engine temperature.

When it warms up it idles at around 750 rpm. When you shift from drive or reverse to neutral or park you get a momentary drop (a dip) to about 650/700 rpm and it them returns to 750.

I did replace the IAC (Napa) about 4 months ago for another problem (low idle when warm in neutral or park). The new IAC didn’t immediately to fix that problem (but, for some unknown reason, over time that has healed itself???) except for the dip in idle between drive and park. If you pull the IAC connector (when warm), it stumbles, fumbles and stalls. I have looked for vacuum leaks; but, didn't find anything obvious.

Any ideas/help would be appreciated, Ed

 

[swynx]

Gas saving feature

 

[RonD]

Try this.
Before turning on the key, push gas pedal to the floor and then release it.
Now try starting cold, see if it behaves normally.
Maybe the TPS is getting worn(dead spot) at throttle closed position.

Second test.
Turn key on, wait 3 seconds, then turn key off
Repeat 3 times.
Now start engine and see if it starts normally.
Maybe check valve in fuel pump is allowing fuel pressure to drop when it sits.
Pushing down on gas pedal(engine running) starts fuel pump again.

 

[adsm08]

You can also try cleaning the MAF. If it's heater is getting lazy it could do that, cleaning may help.

 

[kimcrwbr1]

Maybe try cleaning the throttle body around the butterfly. Just open it by hand a wipe it with a rag with a little solvent on it. That will allow more air in when the computer drives the idle air valve open. Have you changed the PCV lately if applicable. Just change it when you do your tuneups it is cheap.