DarkJester

Hey all,

2000 Trans Am 27,000 miles LS1 (durrr)
It threw a P0420 code, no other problems, did it after I was playing around on the exit ramp. Cleared the code, now it won't start every time. I played with VAT's, measured the key pellet at the connector. reconnected and the car starts right up.
Also, If I turn the key on and off several times it will finally start. Once it starts, it will start reliably back to back.
BUT, if you take the key out and let it sit for a couple of hours, it goes back to the cranks won't start routine, until you try several times, etc.
There was the one time I slammed the steering wheel to the bottom of the tilt to see if it would start, and it did.
Probably a red herring...
I'm not driving my car because I don't want to get stranded, which sucks.
SO!

1) Fuel Pump? I can hear the whine when I turn the key. Haven't put the gauge on it yet.
2) VATS? did I screw something up with the BCM when I cleared the code? (Oh yeah, I did the relearn procedure (11 minutes on, 30 seconds off, etc) it worked once.)
3) VATS II, do I have an intermittent read of the pellet? Ya think?
4) Fuel Filter. To my knowledge it's never been changed. Should I just go ahead and "shoot and holler ****" and change the filter?
5) Battery? I have read tales of a weak battery doing this. Enough to crank but not enough to crank and run the injectors/fuel pump.

Any of y'all heard of this before?
I know when the fuel pump went out in the Silverado, it was hard to start one time, then it died completely.
Had to tow it and replace the fuel pump.

tell me some of that experienced tech stuff.
I have a gauge set and I'm going to do a pressure-leakdown test tonight, I hope.


Jester

00pooterSS

iTrader: (40)

Sounds like vats, do the resistor bypass and go from there.

Clearing the code won't have anything to do with it unless the idle parameters were cleared and the IAC isn't opening enough for the engine to fire, you could test for this by lightly opening the throttle while cranking it and if it starts every time then you know that the IAC isn't letting enough air in while cranking and needs to relearn. All you'll need to do there is let it idle in park for several minutes, then in gear. Then put it back in park and turn the a/c on and let it idle for a few minutes then put it in gear and let it idle for a few minutes.

If the car is an auto do the above, if it's a manual let it idle in gear until its warm then turn on the a/c and let it run for a few minutes. Then in either case, after doing the above, take it for a little drive and let it relearn.

DarkJester

Thanks so much for the reply.
Sometimes it just helps to bounce ideas off of someone else to help get things right in your head, ya know?

I do have some resistors prepped for the bypass.
I'll try that tonight if i can get home at a normal human hour from work.

I did the idle relearn right after I cleared the codes, but good call on that.
I'll also try the POT during start to see if that works.

I would just hate to have to drop the tank. I have issues cutting the hole. might be a good excuse to update the rear end though...

Jester.

thunderstruck507

iTrader: (18)

Could also be leaking injector, cam sensor, or perhaps a bad relay on the circuit powering the PCM

coorvette

You mentioned you slammed your steering wheel to the lowest tilt level and it started, there is an issue common with chevy trucks when the security light comes on because a connecter underneath the steering clam shell comes slighly loose enough to only work intermittently and/or at different stereing tilt. In trucks the car cranks for a second and stops, mine did this once but drove fine with the light on other times. Might not be your problem but it could be worth investigating.

David

Edit i should read slower and learn the VAT acronym for the system lol, seems like you already have the shell off and have unplugged and reconnected the security connector, ive seen some shove a zip tie in the connector to wedge it in, but i would think reconnecting it would also solve the issue

DarkJester

As A follow up.
It's fixed.
I won't bore you with all of the troubleshooting involved.
If you want to know, let me know and I will share.
It was the Ignition Relay.


Jester

fst100

iTrader: (5)

thanks for posting the solution! it may help out others in the future when they may have similar issues and can come across this thread.

00pooterSS

iTrader: (40)

Seriously, it's nice when someone posts a follow up, almost every help thread ends without the solution being posted.