Decresed Idle Speed

chevrolet
1500

#1

I have a 2003 Chevy Silverado 1/2 ton pickup. I recently replaced the original battery.Ever since then when I come to a stop sign the R.P.M drops like It’s going to stall. The battery cables are tight and I had diagnostics run to check the alternator/ with and without a load, Starter and battery . All checked out fine. It did not act this way before the battery was changed.Any ideas as to why?


#2

Well, one does have to consider the possibility of complete coincidence.

After you come to a stop, does it continue to act like its going to stall, or does it eventually right itself? What is the idle like you just sit idling after starting it up?

Sit at idle without driving and stomp the brake pedal. Does anything happen to the idle? If so, have the brake booster inspected.

Is this an automatic? If so can you turn overdrive off? (O/D Off button or something?) If you can try driving around with the O/D off. This should keep the torque converter from locking up and the problem should be gone IF it has anything to do with the torque converter clutch having unlocking problems.

Clean the throttle body and the idle air control valve. Even if this isn’t the problem, its not a bad thing to do anyway just as general maintenance.


#3

Thanks for the quick reply. To answer your questions- 1. Both, but not a full recovery.
2.Seems normal. 3.Applying the brake without driving has no effect. 4. It is an automatic,
4x4. There is no overdrive switch to turn off. What about a fuel sensor problem? It seems like it’s something electronic that’s not maintaining the speed but that’s my guess. I notice it when I put it in gear, either forward or reverse and at stop signs.I used a cleaner.The truck runs great except for the idle.


#4

The problem might be that the adaptive memory in the engine management system has to relearn all the parameters again. And this may take time. This sometimes happens when a battery is disconnected.

You can read what problems can arise when disconnecting a battery on a vehicle with computers/modules here. http://www.aa1car.com/library/battery_disconnect_problems.htm

Tester


#5

To reset the computer you can disconnect the battery again and check the manual for advice as far as driving conditions suggested for proper learning by the computer. There is an after market device that plugs into the cigarette lighter during battery disconnects, but too late for that now, posted as a note for the future if needed.


#6

Thank-You So much ! I believe you have nailed my problem. I never gave it a thought.
I will purchase the 9v adapter for future reference . I’ll drive it a few days to see if the normal operation returns. I not I’ll have to go to the shop. Thanks Again !