I have posted this in a couple places--hopefully someone can help.

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I have been recently experianceing a weird problem. One day last week I parked at the parts store and when I came out the car started fine, then when I was backing out it stalled. It cranked a couple times then started. Almost sounded like it had overheated or something, but it definately was not. Then at the next light as I accelerated away it stalled again and took a bit more to start this time. I drove it home and opened the hood to find nothing strange or out of place. Later that day I drove it about 50 miles and toward the end of the drive it stalled pulling onto a side street. It cranked over a few times then started up. No problems for about 2 weeks except for some very LIGHT stumbling on steady speed cruising or light acceleration. Very slight and no-one riding with me even notices. Then Saturday after a 30 mile drive I stopped to get gas. No problems (except the slight stumble) til afterward. I stopped at a light and it stalled. Fired right back up like nothing was wrong. I continued home (about 15 more miles) without any problems. Then this morning I start it up in the garage and it stalls after about 10 seconds and is hard to restart. Finally does and then stalls again. Get it reluctantly started and it drove fine all the way to work except the very occasional very slight stumble. I am not losing or lacking any power because I ran my best times after the first episodes.


Here is what I know--I have a Walbro intank 255 fuel pump and it is kicking on, no problem. I have another inline fuel pump that is also kicking on fine and producing plenty of fuel pressure. I recently had the whole front of the motor apart to replace all the seals and gaskets as well as the intake and oil pan gasket.

Any ideas?? I am afraid it is going to do it once and not restart. I am sure it will be raining and I will be far from home when it happens too.

 

Not giving a SES light? I had a similar problem, but my SES light came on, it was the spark plugs and wires. The headers burnt through them.

Travis

 

i'm sure you've been told this already, but what i've always been told about why a car wont' start is that its either compression, fuel, or spark... you have fuel, you probably have compression, so i'd check spark...

 

This is just my .02 cents but it sounds like the IAC valve on the bottom left of the throttle body is dirty/bad. You can pull off the IAC valve and clean it (GM recommends their special cleaner but im sure a electric parts cleaner spray from R.Shack will do it) and if that doesn't fix it you may have to replace it. The attaching screws are torqued at 27inch lbs if you use one.
After you clean it and re-install it, you have to press the gas pedal slightly, start car, release pedal, run car for 5 secs, shut off for 10 secs then restart and check for proper idle operation.

If you buy a new one you have to measure the distance between the tip of the IAC valve pintle and mounting flange before you install it. If it is more than 28mm you have to slowly push the pintle in. Then after you install it follow the above gas pedal thing.

again just my .02 cents Kumar

 

Clogged catalytic converter...
pluggs and wires...
bad gas...
clogged fuel filter...
Opti: going, going, gone...

Check out those.
STEW

 

It cannot be the cats becaus I dont have any. The IAC adn TB are clean the filter is new the EGR is not there and is bypassed in the computer the rear o2 sensors are gone and bypassed, I have spark, fuel and compression. Otherwise it would not start back up. Been through multiple tanks of gas since the first episode and the plugs and wires are new and not touching the headers. The neutral saftey switch is bypassed, the AIR pump is gone and bypassed and the fuel injectors are new SVO types. I dont have an aftermarket ignition. The actual fuel pressure is sitting at 41psi after the regulator and the tires are inflated to 32psi.

I bought a new Opti OEM Opti for $200 and will be installing it soon. Wish me luck.

 

So did the opti do the trick?

Old thread is old but so is my car. It's doing the same to me. Gotta diagnose it at least before I can take it to a shop.

 

Dude,
I've fixed a Plethora of LT1's in the Chevy dealerships during the 90's...
The older style 92-94(early) non-vented... well its Florida, and the cap was cross-firing from the moisture...(Corvette nuts washing the engines, or the Camaro guys plowing though the flooded streets of summer)
BUT the newer style has a vent system that was designed to "Fix" the problem... HA
When the vent system stops working,(Check valve quits) you have a chemical reaction,
The hydrocarbons (Blow by) enter the back of the dist. and react with the ozone that the spark makes jumping from the rotor to the dist cap...
Acid, this acid brakes-down the plastic components of the photo-cell, and the cap / rotor, (even though the Caps are made with a style of "Bakelight")
So when you replace your 94 to 97 Opti Spark, please check and see if there is vacuum at the fresh air duct, when the engine is idling. (the hose few inches from the TB, black 5/32 hose with a blue 90)
This Vac harness is still available from GM P/N 12552426
If you are lucky like me an have a GM scan tool you can see if the High Resolution counts / Low Resolution counts drop when it stalls, or mis-fires.
Hope this helps...
PS> Run a LS1 (24X) processer, and LS2 coil packs on your LT1 and you wont have this problem... Check this web site out!!!
http://www.eficonnection.com/24x/default.htm

 

I am experiencing the same problem with my LT1 . Did you resolve this problem? in both cases for me it was right after topping off the tank