1993 XLT 3.0L really low idle

[austinrick]

I replaced the battery in my '93 a couple of weeks ago. It was a routine swap.

Next time I started her up to go somewhere the first thing I noticed was the idle: it seemed that nothing was boosting it even at startup/warmup. I mean it was and is idling as if there is no low idle stop; I worry a little about oil pressure. Granted, it's been hot lately, but in 27 years of owning the truck I've never known her to idle this way.

When I turn on the a/c the RPMs surge a little to compensate for the load, so that much is working.

Going by my Hanes manual I just measured voltage and resistance at the Intake Air Temperature Sensor (mounted in air filter housing) and the Idle Air Control solenoid. Readings were all right around the numbers called for, except for the IAT sensor, which I couldn't get the probes on properly (voltage at the connector was good, tho).

Do I have a real idling problem, or is this somehow normal with a new Gold Top battery and summer temps?

Should I go ahead and replace the AIT sensor? -thanks

ps- I bring the battery into it thinking maybe the new one has reduced the load on the charging system and so reduced the need for a higher idle. It's just a theory.

 

[franklin2]

Your computer was reset when you took the battery out. You will have to drive it for a few days for it to relearn and compensate for different things.

You can keep driving it and see if the computer pulls itself out of it, or you can take the intake hose off and clean around the throttle body really good and take the idle air control valve out and clean it. Then your idle may be too fast, and again, the computer will have to relearn things after a couple of drives and stops.

 

[austinrick]

Thanks very much for that. After reading your reply I went out and started the engine; it idled very slow, then the RPMs picked up some, briefly then settled down again much like I've been used to. I pulled the connector off the IAC solenoid and the RPMs dropped down to barely running – almost stalled – plugged back in and she recovered. Now I know the solenoid has been working as it should all along and the computer seems to have reset itself.
I've learned a good deal in all of this.