I'm new to the truck section, I'm stompped on a problem that just happend to my truck. I have a 2003 GMC Z71 5.3L recenlty I have added a cold air system and put electrical fans on the radiator. Well needless to say my battery went dead after jaming out for about 3 min with the truck on testing out a new amp. So I jump started it after trying to start it a couple of times then went to the story to go buy a new battery. Well now my idle is going up and down when I turn the AC on and its so low that the AC blows hot and sometimes when I stop the truck turns off. I'v tried reseting the ECM by disconnecting the battery but no luck. My friend said to try cleaning the throttle lied and disconnecting the ECM from the wiring harness. I don't know what else to do other then take it to the dealer and have it flashed.

 

Even without an optima red or yellow top, it shouldnt have that low of an idle and still stall on you. I would say the battery you need is a yellow top since it sounds like you have a pretty kick *** system. But... also, did you install a new pcm or do any tuning recently? If so, you might need to get it flashed. Also, check your grounds and maybe have someone check your alternator too. Good luck, let us know what you find.

 

I have not done any tuning to it other then cold air system and electic fans which woke it up. I was loving the mods untill this problem came up which one of my friends has heard that on new cars and trucks when you jump start you can zap the ECM and throw it off timing or calibration dont know if its true but their way I have to get it fixed.

 

Check and make sure that the air intake tube is totally tight and isn't leaking anywhere, and maybe try cleaning the throttle body. Sometimes when I disconnect my battery it takes a few miles for the PCM to relearn idle, but it shouldn't take too long.

 

Cant help but to ask before I go looking for the ECM is it located behide the glove box I know where the one for My TA is on the fender wheel. But I have not had to mess with the one on my truck.

 

Never mind I found the ecm its next to the battery I'll try disconnecting it and see what it does.

 

Well thanks for all the info. I went outside disconnected the ecm cleaned the throttle body let it sit for like 5min and turned it back on. She's back to normal of course the power is not there cuz I know it has to relearn the fuel curve and all that but the idle problem is gone. I feel so much better I couldn't even sleep last night thinking about what to try. Thanks for all the help its nice to have forums like these that actual people do relpy and help out. Unlike tech lines and dealers that all the want is your money.

 

Cool deal, glad it all worked out

 

There is actually an "Idle relearn proceedure" for when you disconnect the battery or replace the PCM. It goes like this.

Start truck and get to operating temp. Set parking brake, block wheels and put it into drive for 5 minutes. After 5 minutes, put it into park and let it run another 5 minutes then you are done.

This from my Helms Manual.