99 GT hard start when warm [Archive] - GrandAmGT.com Forum

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mjtr21
09-21-2008, 12:30 PM
as the title says i have a 99 GT that is hard to start when warm. it starts fine when the engine is cold. but if the engine is already warm and i start it, it will start but stall out. sometimes if i get lucky it will start but the rpm's will jump up and down like its going to stall. i have no clue what it is. i have changed the air filter and fuel filter and it still does it. please help.

mjtr21
09-21-2008, 01:03 PM
okay i was searching around and it seems like there is some sort of reprogram that the GM dealer can do to the computer. maybe this would work. otherwise i could try the "wait 3-5 seconds in ON then start" thing.

Malaclypse
09-21-2008, 04:28 PM
First I"d try getting your PCM reprogrammed as you mentioned and if that doesn't work try an injection flush and have your fuel pressure regulator looked at to make sure it isn't leaking.

gagt Mechanic
09-28-2008, 12:38 AM
coolant temp sensor. if your engines cold and you start it it may not be rich enough to cause a problem, when warm your engine needs less fuel and if your cts is going bad it could be telling your pcm its alot colder than it is, thus flooding your eng.

new1976
09-13-2010, 04:22 PM
Hey mjtr21, did you figure out what was wrong with your engine because mine just started doing the same exact thing including the rpm's going up and down when i do get it to start.

bricooper78
09-13-2010, 04:52 PM
mine has done this since i got it, and i've actually tapped the gas a couple times (i know, i know..don't start) just out of trial and error, and it started.

it shouldn't be done, and it shouldn't help...but it does, so i do it. and when it blows up, everyone stand in line and tell me that's what did it lol and i'll take my lumps

mjtr21
09-13-2010, 05:09 PM
Well I did a tune-up on the car and that seems to have helped, but not completely fixed my problem. It doesnt do it as often but still once and a while. That's what I've done was pushed the gas pedal a little bit and it starts no problem. I've noticed this with quite a few GM vehicles though including a friends Impala and brothers Monte Carlo which have the same engine.

new1976
09-13-2010, 05:13 PM
mine has done this since i got it, and i've actually tapped the gas a couple times (i know, i know..don't start) just out of trial and error, and it started.

it shouldn't be done, and it shouldn't help...but it does, so i do it. and when it blows up, everyone stand in line and tell me that's what did it lol and i'll take my lumps

yeah, i've done that a few times myself to keep the car running if the rpm's keep fluctuating or it just won't start n sometimes it makes a somewhat loud bang lol. :banghead

bricooper78
09-13-2010, 05:17 PM
oh man i didn't think to mention that part:

i did the 100K tune up-plugs, wires, also had a rusty coil pack of all things, so changed them, battery, uh coolant, seafoam'd the entire fuel system and engine, changed fuel filter, and it didn't seem to make a lot of difference.

oddly enough, since i stuck the cold air induction (which i am still messing with but i do not have a stock air filter or box)on this thing, it seems to take a warmer day for it to need the gas pedal touched to fire up warm.

so i'm stumped, i didn't want to chase a thousand sensors, so i touch my gas lol

bricooper78
09-13-2010, 05:20 PM
1976--mine doesn't fluctuate revs... mine just doesn't wanna start.

the bouncy tach used to be caused by an idle air control sensor, 28 dollars to change, but that was the old 2.8, i never priced it for the 3.4

FromTheInside
09-13-2010, 05:34 PM
My car does the same crap. When the car is warm, I get into the car and push the pedal to the floor. Then I put the car to on and wait a few seconds as others do as well and while still holding the pedal to the floor, I crank and release the pedal within 1/2 a second and it starts up normally pretty much all the time.


We should test our IAC valves first.
http://www.automotiveforums.com/vbulletin/showthread.php?t=663849

bricooper78
09-13-2010, 05:47 PM
wow man, i only tap mine, like maybe a second, and only quarter throttle at most. mine just needs goosed lol

new1976
09-13-2010, 05:58 PM
thanks guys, i'll check into the IAC thing. i haven't tested out the 3 sec start thing yet either but to me something is wrong so i'd like to fix it instead of working round it if it's a cheap option like reprogramming the PCM like some have suggested.