this happens sometimes on cold startups (car temp, not air temp, it's 75ish outside right now)

if it doesn't start normally, it will either stall like you see in the video, or it will start and act like it's misfiring on one cylinder (backfires a bit and acts like it's not getting enough gas?) if it does the misfiring bit 99% of the time if i shut it down and restart it, it's fine. also most of the time unless its cold out (50-60 deg like last week) it would stall out 2-3 times before it started. does this sound like a fuel pump problem? the car has 141k on the original pump FWIW.

i meant to say if i shut it down and restart it after it runs rough, that it runs fine after that.

 

Have you checked the or changed the fuel filter

 

fuel filter was changed last year approx 5k miles ago

 

That sounds like a very accurate description of what my LT1 acted like with a bad ignition switch.

 

I'm banking on the coolant sensor in the waterpump being bad.

 

why would the coolant sensor have anything to do with it? FWIW the waterpump is only a couple years old.

the igntion switch i hadn't thought of but VATS is currently bypassed because a few months ago the car wouldn't start and the security light came on. after a few mins the car started but the security stayed on and wouldn't go off even by switching keys. i figured the wires inside the lock cylinder went bad and went ahead and just bought one of those $20 VATS bypass plug in modules from ebay so my car always gets the correct pellet resistance. This issue was occuring before VATS ever started acting up so i don't think it's related to the VATS bypass.

Also, when the car starts and runs rough like its misfiring, there is no SES light on the dash.

 

"And finally, the important one which can cause many problems if its
malfunctioning. The Engine Coolant Temperature Sensor is the sensor
which supplies the PCM with coolant temp information. If this sensor is
faulty, it can cause many drivability problems with your car, but the most
common is hard starting. It’s located on the front of the water pump."

I had a hard start problem and it ended up being this sensor. Worth a try.

 

when the car fist starts up it is using the open loop vs load vs coolant temp so if the coolant temp sensor is bad your not getting the correct A/F ratio. But once the O2's come on line it switches to closed and and the open loop table is no longer used

 

but i doubt 1/2 a second is long enough for it to go into closed loop. most of the time if its warmer than 70 or so the second turn of the key makes it run fine. its like there is enough fuel for it to run just for a split second. could the fuel pump be binding up somehow then getting jarred into working after the initial stall?

how hard is it to change that coolant temp sensor?

 

its in the water pump if I remember correctly.....also it will always run in open loop till the O2s come upto temp. You shut it off and start it right back up they take a little bit to heat back up. I turn on my wideband before I start it and I can tell when it switches into closed loop everytime. And it maybe take 10-15 secs even if its been running.

 

fwiw it was 81 degrees yesterday afternoon when i started my car to check it and it started up fine. i hadnt driven it in roughly 18 hrs.