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1999 Chevy Astro intermittent no start

I’m working on a 1999 Chevy Astro 4.3L with an occasional crank, no start condition. On any given day, this vehicle will start right up and run fine, although some days it will start right up and have a part-throttle stutter; not a dead miss, but a stutter when accelerating that sometimes goes away. When it has the stutter, disconnecting the MAP sensor will cause the stutter to go away completely. I replaced the MAP sensor, but nothing changed. Today, it’s back to its crank, no start attitude problem. The basics check out fine: good, strong spark at the wires, 60-65 psi of fuel pressure, and I even pulled the plenum to verify fuel is firing from the injectors. Everything seems to be happening as it should except that it will not start and run. I even tried doing the Passlock relearn procedure on it, despite spark and fuel happening when it should, one or both of which would normally be eliminated by the security system, but to no avail. What could possibly cause this here-today-gone-tomorrow no-start condition?

Bump.

Stupid question: I would like to remove the ignition switch to inspect it, but I cannot seem to get the lock cylinder out of the column, which has to happen to remove the upper shroud and probably the switch itself. I assumed this one was like every other domestic of this era and you used a punch to push in the pin located in the extra hole at the bottom of the column with no hardware in it, but tried that and it won’t work. I tried this with the key in all positions and nothing worked. Is there a secret to this particular one? Does the steering wheel have to come off like the old GMs?

Here are the (final) steps for removal from alldata;

Turn the ignition lock cylinder to the START position. Using the bent tip awl, push down on the ignition lock cylinder retaining pin.
Release the ignition lock cylinder to the RUN position.
Remove the ignition lock cylinder from the lock module assembly by pulling the ignition lock cylinder away from the steering column.

I got the ignition switch out of there. The steering wheel did have to come out to remove the switch, but not to remove the lock cylinder. The retaining pin is in the top, not the bottom, which is why they suggest a bent tip awl. I used a 90 degree pick once I figured out where the pin was. Still not sure why there’s a random hole in the bottom column cover other than to deceive you into thinking that’s how to remove the lock cylinder since it’s that way on Ford and Chrysler vehicles. Once I got it hanging by the wires, I decided to try to start it, and it did start. It hasn’t been starting for the past two days. Not sure if fiddling with the switch caused the vehicle to start or not.

For what it’s worth, there is one odd behavior I noticed about the no-start condition that caused me to suspect the ignition switch. I noticed that when the vehicle will not start, sometimes the engine will give a brief “kick” or “shudder” after cranking when I turn the key off (not when I release the key, but when I turn it back from “run”, which can sometimes be a couple seconds after cranking has stopped and it will still give that shudder), but will not fire or attempt to start at all during cranking (note that it does have spark and 65 psi of fuel pressure, and removing an injector and cranking showed a nice spray pattern). Thoughts?

While it’s on my mind, I figured I would post the solution I found for this issue:

The van decided to refuse to start for about a solid week for me. During this time, I determined the familiar clicking of fuel injectors firing was not present during cranking, but I chose not to test them as I had before due to the amount of work it takes to access them on this engine. I began to suspect the cam position sensor since that is the signal the ECM uses to drive the fuel injectors. During an unrelated trip to the salvage yard, on a whim, I purchased a distributor for a 4.3L figuring, at worst, it would not solve the problem and I would be out seven dollars and ten minutes of my time installing it. The distributor on this engine houses the cam position sensor. I installed the used distributor, and the van fired right up and ran perfect. All issues have been resolved since replacing that distributor, so I think that was it. Thanks to all for your thoughts and consideration.