dieing when coming to stop

[ballzac86]

my parents crap hauler/trailer puller rig's battery died when they dropped some stuff off at goodwill. i went over to jump them with the ls, and after a while, finally got it started. on the way home, i cut through a neighborhood and when i came to a stop sign, my car died. i put it in neutral and it starts up fine. its been doing that ever since that night(2 weeks). it mainly does it if i slow down quickly from above 20mph, but not always.

last night, i put it in D4 instead of the usual D5 i drive in, and it only died once, instead of 3-4 times like it does when its in D5. on the way to work this morning however, it died in D4 just like it does in D5. if i rev the engine up while braking, it wont die, but thats great on the brakes lol. has anyone ran into this problem before? i figured that i would ask on here before calling around to get estimates from a local shop.

i sure as hell wont be jump-starting anyone in my LS anymore. ill drive the jeep.

 

[decibels5]

I have had a similiar problem, but with a different car. Possible causes I came up with were, plugs, wires(not for the Ls), coils, throttle position sensor, mass air flow sensor, fuel pressure, and vacuum lines.

 

[ballzac86]

so you never got it fixed or what? i figure its electrical, because in having it since september, i havent had any problems what-so-ever with it until right after after i jump-started their van. it took a while to get their van started.

it runs perfect otherwise, just seems to shut off if the rpms go lower than 500 when the tranny is downshifting.

 

[NateRW21]

so you never got it fixed or what? i figure its electrical, because in having it since september, i havent had any problems what-so-ever with it until right after after i jump-started their van. it took a while to get their van started.

it runs perfect otherwise, just seems to shut off if the rpms go lower than 500 when the tranny is downshifting.

I'm just taking a stab at this one; it's a tough one to diagnose site unseen... Perhaps the draw on your electrical system messed up your alternator...

 

[eastcoastLS]

not being critical at all..
if you read the owners manual, it says for jump starts to put the positive on the red terminal as usual, and then the negative (black) on that little screw that screws into the spare tire well. my dad told me once you could f@ck your sh!t up if you hook ground the jump start to the battery. with that being said, i've only jumped started 1 car with the ls and grounded it to the battery. nothing happened

 

[ballzac86]

oh i know youre not supposed to, but my trunk light is out and didnt figure it hurt it just once. ive never had a problem hooking it straight up to the batter in the other 10+ cars ive had haha.

anyone else have any ideas?

 

[nickandersonLS01]

Maybe I'm completely wrong and electronics are completely different with cars, but the negative battery post is just a connection to be grounded... Therefore it shouldn't have any affect if you put the negative jumper cable on it or on any other ground... In fact the negative battery post should be one of the best places you can find for it, seeing as its connected directly to the chassis.

 

[NateRW21]

Maybe I'm completely wrong and electronics are completely different with cars, but the negative battery post is just a connection to be grounded... Therefore it shouldn't have any affect if you put the negative jumper cable on it or on any other ground... In fact the negative battery post should be one of the best places you can find for it, seeing as its connected directly to the chassis.

The reason for connecting the ground lead on the dead vehicle to the frame/engine is for one simple reason: it's the last connection you are supposed to make and you don't want to ignite the hydrogen out-gassing when the sparks occur which always do when you complete the circuit.

For reference, order of connection should be:
Pos, good car
Pos, bad car
Neg, good car
Ground, bad car

Something to note is that some cars specify shutting off the ignition while others have jumping points away from the battery which are on an isolation circuit to prevent a surge through the electrical system, damaging delicate electronics. Always check your owner's manual for jump starting procedures.

 

[SoonerLS]

The symptoms you're describing sound like a fouled idle air bypass. I think it's called an IAC on the LS; it's a small valve that's supposed to open to keep the engine from dying when the butterfly valve in the intake closes and cuts off the airflow. I had the same symptoms you're describing with my Explorer; I took the idle air bypass off and hit it with some Berryman's ChemTool, and it hasn't been a problem since.

I think Quik posted a picture showing the location of the IAC within the last few months.

 

[MaroonLS]

Ive been having the same problems with my 01 ls it all started after i put on my cold air intake, I made it out of 3" alum. tubing some times it wont die at all when driving it but sometimes it'll die at every stop sign, it will die every time in rev. if i run it up to the speed limiter and let off and coast, I thought with the 3" tube that it wasnt pulling enough vaccum but I dont know, I dont have any leaks Ive fixed all of them, I ran out of ideas. where exactly is this by pass valve. thanks for the help..

 

[NYC LS8]

Should be mounted to the throttle body.

 

[brentalan]

With the cold air intake, the car's MAF readings will be messed up without a computer reset. I think it would relearn over time but you might want to disconnect the battery and let it relearn the settings. Don't be dicouraged if it dies the first few times back out. Eventually it can relearn and sometimes fix the problems. This may be something that ball sac try too. Certainly can't hurt in his case.

 

[daves2000ls]

Be careful if you take the IAC off, it has a thin paperesque gasket that might be brittle. I broke mine, actually, I dropped it, lost it, then found it in my bumper, yup IN, then I reached in to grab it and snapped it. Cost for a new one, $3, and not being able to drive until it comes in.

 

[MaroonLS]

Ok so it is the thing that has the big line coming into the front and a smaller line on the driver side of it and an electrical plug on the passenger side, sorry for ignorance but I'm used to pre '85 vehicles

 

[Quik LS]

right - the IAC (idle air control valve) allows just enough air to slip by the closed throttle plate to prevent the engine from stalling. There is a little motor in the valve that constantly adjusts the valve opening to keep the car at target idle rpm.

On the pre-03s - there is also a added complexity - where a air feed comes off the IAC to an air rail on the intake manifold - that also feeds the injectors.... The injectors have a air port about 1/2 down their body, which allows for better atomization of the fuel mixture.

 

[MaroonLS]

Thanks Quick