VEC-3 Computer 'Relearning'

[TexasPettey]

I had the battery disconnected from the car to retighten the headers this weekend. After starting back up, it's having trouble idling. When I run it, it bounces around at idle, sometimes stalling out. I had the same issue the first time I had it after the mods were done. The folks that did the tuning said that it was the stock computing having to relearn the car. Last time, it disapeared after ~200miles. I've got a VEC-3/heads/708-CAM/Headers/ROE Exhaust/ROE SC. Is this something that is likely to happen every time the battery is disconnected from the PCM?

 

[1TONY1]

Did you do switch on, depress throttle to the floor a few times then switch off...BEFORE you started the car ? This is supposed to tell the pcm what the perimeters are on the throttle position. I have done it and not done it without much difference but it's something you could try after disconnecting the battery (again )

And yes I have seen the need sometimes for it to relearn the idle, but the idle is never to far off. It seems like if I bring the car up to XXXX rpm and let it come down to find idle it will start getting better. After doing this 5/6 times the idle seems more stable....at least when coming down.

 

[agentf1]

I was talking to the Wizard Chuck Tator about disconnecting the battery in order to get my key fobs reprogrammed and he told me to expect this to happen after the battery is disconnected. He said just keep it running withthe gas pedal and that it should go away quick once the computer relearns. So I would say it is normal/expected. Not sure how the VEC-3 effects things.

 

[KenH]

The VEC3 has no ability for adaptive learning, only the factory PCM does that.

 

[TexasPettey]

Thanks. I did play around with pressing the pedal with the engine off but key on a couple of times today. It didn't fix it directly, but it may have helped some. It is back to normal idle now. What a pain.

 

[RAYSIR]

Thanks. I did play around with pressing the pedal with the engine off but key on a couple of times today. It didn't fix it directly, but it may have helped some. It is back to normal idle now. What a pain.

One of these days guys will learn to plug a battery, even a 9 volt, jumper onto the cig lighter or connect a seperate battery to the jump terminals before disconnecting the battery to keep the computor alive. I disconnect my battery for the winter and my 98 runs bad for a few miles, dies, stalls, but it soon runs great.

 

[TexasPettey]

One of these days guys will learn to plug a battery, even a 9 volt, jumper onto the cig lighter or connect a seperate battery to the jump terminals before disconnecting the battery to keep the computor alive. I disconnect my battery for the winter and my 98 runs bad for a few miles, dies, stalls, but it soon runs great.

Something could probably be rigged up to keep a heartbeat voltage to the PCM only, but you'd have to isolate it from the rest of the car's wiring. If that big lead-acid drains out over time, a little 9V won't last long.

 

[RAYSIR]

Something could probably be rigged up to keep a heartbeat voltage to the PCM only, but you'd have to isolate it from the rest of the car's wiring. If that big lead-acid drains out over time, a little 9V won't last long.

Right On , the 9v is only used while cleaning or changing batteries. I use a battery pack if a day disconnect.

 

[Canyon707]

I would like to know more about this issue and the way to keep the pcm alive I have an 04 and the manual always says to disconnect battery when doing most mods. how do you keep it alive without damaging it?

 

[ViperTony]

I've disconnected my battery/PCM a number of times and never had a problem with it relearning fairly quickly. After a day of spirited driving its back to normal.