Astro misfire caused by crank shaft sensor?

I apologize up front for the length of this, but I feel like I need to give a little background for the problem.

I have a 2002 Astro. About a year ago, I put all new spark plug wires, spark plugs and had a new Summit distributor installed. About six months ago, the intake manifold gasket started leaking so a couple of weeks ago, I had a local mechanic install a new gasket (I didn't have time to tackle the job). When I got the van back, the Service Engine Soon light was on. According to mechanic, the code was for the Crank shaft sensor. He advised me to drive it and not worry about the light being on. A couple of days later, it started missing off and on. There's no rhyme or reason to when or why it misses. One time you may crank it and it will run fine the whole time you drive it...the next time it will miss (missing usually happens when cruising or easing into throttle) the whole time you drive it. It will miss on wet days or dry days, cold or warm...doesn't matter. I took it back to the mechanic (concerning the missing) and he suggested new plug wires (they're only a year old) and perhaps a new coil. I checked over both, they seem to be in good working order. I hate to just start throwing parts at the van. I've cranked it at night and checked everything over to make sure there's no arcing and have seen nothing. I even misted the coil with water to see if I saw any arcing.

Ok, here's my thinking... According to my Hayne's Repair Manual, if the Camshaft position sensor is bad, it will cause the van to stumble or misfire. However, that sensor is only about a year old (came as part of Summit distributor). I checked the Crankshaft sensor with an ohm meter and it came just short of peaking out the meter. Since I'm receiving a code that mentions both sensors, could it be that the Crankshaft sensor is causing an issue with the Camshaft sensor? Could the crankshaft sensor cause missing by itself? Or...I also read that anytime one sensor is removed, a "relearn" must be performed. I know the mechanic had to pull the distributor to put in the new intake manifold gasket. If he didn't perform the relearn, would that be the cause of my problem?

I know autozone can read the codes for me, but can they perform the relearn or will I need to take it to a mechanic for that? Any help would be really appreciated!

First we need to know what DTC's are in memory before any kind of diagnosis can be made. If the crankshaft position sensor or timing cover is moved, removed, replaced, or disturbed in any way, the crankshaft position sensor relearn must be performed. Whenever the distributor is removed, camshaft retard should, at the very least, be checked. The el cheapo scan tools that the auto parts stores use are not capable of either operation. What I would suggest is have Autozone, etc, retrieve the DTC's, write them down in the order that they are retrieved, (very important) and post them here. Don't let the parts guy sell you anything until we diagnose the problem.

OK, here's the lastest info. I just drove the van to town to have the code read (drove for about an hour without a single misfire). The only code in the memory was a P1345. I had it erased and the SES light did not come back on until the next time I cranked the van.

If I understand correctly, this code is thrown when there is a fault between the crankshaft sensor position and the camshaft sensor position. According to what I read, this could be caused by the distributor not having been reinstalled correctly (1 tooth off in either direction, even). The mechanic swears that there is only one way for the distributor to go back in and that if the timing were off there would be a constant misfire...not one that comes and goes as mine does.

So, here's my questions based on all of this:

First, if the crankshaft sensor were bad...would it cause misfiring at all or just a fault code with the SES light coming on?

Second, if the distributor wasn't reinstalled correctly, would it cause a constant misfire or one that comes and goes?

Finally, is there a way for me to check/adjust the position of the distributor without actually having to remove and reinstall the whole assembly?

I really don't want to have to take this back to the mechanic as I'm not so sure I trust what they've been telling me. I thought it was all very odd to begin with that the Crankshaft position sensor just happened to go out while they were working on the intake manifold gasket. Thanks for your help!!

By the way, unless they had to turn the crankshaft to find TDC, I'm pretty sure that nothing in the area of the crankshaft sensor was tampered with during the intake gasket replacement. The only thing that would have been moved/removed was the distributor.

P1345 is set when the distributor is not installed correctly. The distributor drive gear has 13 teeth, each tooth accounts for ~27 degrees of distributor shaft rotation. The PCM watches camshaft retard and if it's off more than ~25 degrees, it sets P1345. The only "fix" is remove the distributor and install it correctly. VERY easy to do IF you follow the instructions. It takes about 10 minutes, nothing to it. Installing the distributor correctly is a "rough" adjustment for camshaft retard. It is fine tuned by rotating the distributor. The distributor base has a smaller diameter than the hole in the intake manifold that it mounts in. This "slop" allows for slight, (~10 degrees) rotational adjustment of the distributor. Camshaft retard is similar to ignition timing and can cause intermittent misfires if it's off a few degrees. Misfires will get progressively worse the farther off it is.

Old_Master, could you walk me through that. I see the bolt with the hold down bracket on the shaft of the distributor. If I loosen that, will it give me the play I need? And, do I just turn the whole thing in one direction or the other until I get it right? I'm not afraid to tackle it, but I've never dealt much with timing.

And, once I get it right, should that clear the code?

I can walk you through it. The distributor must be removed though. There isn't enough "fine tune adjustment" to turn it far enough. The PCM can compensate for ~25 degrees, turning the distributor will only get you ~10 degrees.

I tried loosening the hold down bracket and turning the distributor a little, but it wouldn't move much at all due to the groove that it fits into in the hold down bracket itself. Will I be pulling out the entire distributor assembly and, if so, do I need to find tdc first?

The movement you got is the ~10 degree "fine adjustment". The distributor has to come out, and yes, the crankshaft must be rotated to TDC compression for #1 cylinder first.

Label the wires on the passenger side of the distributor cap so they get put back on correctly. Pull the wires out of the cap on the passenger side. Move the cap out of your way toward the driver side. On the distributor housing, there is a "6" stamped on it:

http://i561.photobucket.com/albums/ss58/cwhook/334555.jpg

Remove the key from the ignition, using a ratchet and socket in the crankshaft vibration dampener, slowly rotate the crankshaft clockwise until the distributor rotor starts to approach the "6", (you'll need an assistant for this). If you pass the "6", do not turn the crankshaft counter clockwise, rotate the crank 2 more times. On the vibration dampener there are two "slots", slowly line them up turning the crankshaft clockwise, paying close attention to the top marks, (the other mark should be in about the 4 o'clock position):

http://i561.photobucket.com/albums/ss58/cwhook/43LVortecFinding1TDC-Copy.jpg

When the dampener mark lines up with the mark on the timing cover, #1 cylinder is at TDC of its compression stroke. DO NOT MOVE THE CRANKSHAFT FROM THIS POINT. Note the position of the rotor in relationship to the "6". It should now be about 20 degrees away from the "6" in one direction or the other. Remove the distributor hold down bolt. Unplug the camshaft position sensor. Pull the distributor straight up, (the shaft will rotate slightly as you pull it up). Rotate the distributor shaft slightly in the direction that it needs to go to line up with the "6". In other words, if the rotor was left of the "6" (in red above), rotate slightly to the right or vice versa. Install the distributor and make sure the rotor points to the "6", (or very close to it) when the distributor housing is fully seated against the intake manifold. It MIGHT be necessary to rotate the oil pump drive shaft, in the same direction, the same amount you rotated the distributor to line it up with the "6". Put her back together, clear the DTC's, and start her up. The P1345 should be gone and no SES light.

Thanks for the walk through! I have one small problem in that one of the screw heads for the distributor cap stripped out when I tried to loosen it. I'll have to cut the head off and get the cap off that way. I'll let you know how things turn out.

Hearing that, it doesn't surprise me they told you it only goes in one way. They probably never took the cap off!

The original distributor housing is made of plastic.... be very careful not to break the "ear" off that the screw goes into. If it breaks.... time for a new distributor. Some aftermarket distributors are made of aluminum, much better design and well worth the extra money.