[90Brougham350]

When I start my '90 after she's been sitting long enough to completely cool, it will turn over fine and fire quickly, as it were about to start. At this point, I stop turning the key and let it spring back to "run," just like you would normally start any vehicle. Once the engine is running by itself, stop cranking. The engine seems to hesitate like it wants to die once I turn the key back, and then it runs just fine. It's not that I'm not cranking long enough, it will do the same if I hold the cranking for a little longer that is necessary. It's always done this, finally wondered enough about it today to ask. Thanks!

 

[N0DIH]

Is fuel pressure low? Can you stick a gauge on it?

Does it have any effect with high fuel level vs low? Maybe the pump is starting to get weak. Just a though. Like a lean mixture.

On my 91 Bonneville it would be similar to that when I had bad plugs, wires or coils.

The 307's would do this often when the front or primary vacuum break would be bad or going bad. It would not open the choke right at cold start and it would stall, then when restarted, start fine. The 307's with all vacuum breaks working would be awesome starting cars in any weather.

 

[90Brougham350]

Alright, the fuel pressure is good to go. I'm gonna check all of the ignition components. I know the plugs have delt with a fair amount of detonation from before I had the knock sensor replaced. Wouldn't hurt to check.

 

[N0DIH]

Check the ignition for sure. Is there a condensor in the distributor? Pinging is hard on plugs. Look for bone white insulators and possibly even damge. Also, make sure the insulators aren't cracked off. They will fall and cover the plug electodes when pointed down. 1990-1991 factory plugs had some issues with this. If very white (no gray at all) it is a sign of running lean.

Make sure you put in the correct knock sensor, they are tuned for each engine. There are freq ranges for them. I have a couple in a GM book somewhere, bummer, no V8 specs.

Is EGR coming in when cold? A leaking EGR will make it stumble and the ECM will have to correct for it, but it doesn't know it is running bad when it is cold, O2 isn't online yet.