Spyder bad idle, stuttering

[2Lieutenant2]

My son did probably the dumbest thing the other day and put a battery in his 99 Eclipse Spyder GS 2.4 l non turbo convertible. Since he did this the car will start up fine then after it is warm the car will idle horrible and when he hits the gas the car wants to die. He had to keep hitting the gas pedal lightly to get the rpms above 1500 then the car seems to run fine. Just for whatever reason I unplugged the MAF sensor and the idle and stutter quit. I took it for a drive and it seemed to run ok but the CEL came on. I haven't gotten the codes read as of yet but going to do that prob today. Before I removed the MAF there were no CEL on.

I've read a lot of posts and can't figure it out, can someone please help

 

[DogWhistle]

Why is that a dumb thing? Young men need encouragement, not discouragement. Work through this with him. I grew up working on my father's cars, and then my own. I made mistakes, but that is how you learn. Obviously, when you unplugged the MAF, "just for whatever reason", you know something about cars. If your son is going to own a DSM, he will be doing MANY more things than just replacing a battery, and he'll need your encouragement.

As for your sputter, the previous owner of our (that's my son and me) Spyder, had momentarily reversed the connections on the battery when installing a new one. That 'zap' damaged the ECU (control computer) causing, among other things, the idle circuit to be damaged, and the car ran extremely rich, even at idle.

If the polarity wasn't reversed, then you may be able to correct an idle sputter on the Spyder by having the correct BISS screw adjustment on the throttle body. There are detailed threads on here about how to correctly adjust that on your 2.4L NT.

This is a great group of DSM diehards. You have resources here beyond what most car owners ever dreamed of. Let us know how you two are doing for progress.

 

[briansmith]

Assuming you just changed the battery and battery only and it was not installed incorrectly the cars ECU is ok. I'm also assuming the car has never had the throttle body serviced. A cars ECU is a learning computer, it has KAM or Keep Alive Memory. When you disconnect the battery you wipe its memory and it will lose idle control.

Disconnect the battery remove the throttle body. Give it a good cleaning of the bore and remove the IAC motor and lance both the bore and plunger then re-install reconnect battery and you should be good to go.