OK, looks like it's a bad part, but not in the way I expected. Here are some pics of new vs old. The new sensor was definitely rubbing against something -- I assume the flywheel. If so, instead of the sensor being radial to the flywheel, it's actually offset and overlapping (front to back with the sensor to the front, flat edge facing back to the flywheel). I can tell this because it's the side of the sensor that shows damage, not the tip. This also means that the functional surface of the sensor is the side, not the tip, so shimming would not have fixed the problem anyway.

New Sensor:


Old Sensor for comparison:


I think the problem is the bracket doesn't properly align the sensor front-to-back. It's hard to take a photo of this that shows the problem, but the angle between the top of the sensor and the bracket is very slightly different between the two.

New Sensor:


Old Sensor:


Not sure if you can see this, but the bracket is pretty much 90 degrees on the old sensor but very slightly tilted (just a few degrees) towards the wire bundle on the new sensor. If I put the brackets on the corner of a counter, the tip of the sensor is pushed out away from the bolts, and that side shows the damage.

I considered just trying to bend it a bit myself, but since the sensor is damaged I'm just going to exchange it. I'll report back if this really does fix the problem.

Thanks,
Matt

 

Yep, the bracket is bent alright. Was rubbing on the TC maybe.

 

New CKP in, and she's running as smooth as butter. I guess the proof will be if the stalling issue is resolved. Funny how it took me ten minutes to install it this time now that I have the "technique" down. I think the non-defective part helped too-- the bolts threaded a lot more easily tonight.

Coincidentally, after I got the CKP in and started it up, the tapping was obviously gone, but I heard a very soft clanging. Poked my head around and finally looked in the fan shroud and found the fan ***'y lying on the bottom of the shroud. Not sure how long it's been there, haven't had any probs with overheating, but there was a decent amount of metal worn away from the hub by the crankshaft pulley-- not enough to matter, and the pulley and serpentine belt look ok. 1 minute fix to get it back on, but man, this truck just keeps on giving!

Thanks for all the help,
Matt

 

Hmmm. I'm thinking locktight on bolts.

 

Not "bolts," just "bolt"! It's the massive one coming out of the crankshaft pulley that attaches to the nut on the fan assembly. I have no idea how it managed to come loose because the threads are oriented so that the normal pulley rotation should tighten them. Could be that all of the shuddering when I was farking around with the bad sensor (no misfires, but very, very rough and lots of stalling) loosened it up-- hard to believe, though. I'm going to just keep an eye on it, see if it's loose in a couple of days.

Matt

 

Check and make sure the clutch actually does it's job. It's spinning pretty good even when the engine is idling, so, has a fair bit of momentum. When you shut the engine off, that fan still wants to spin, and now, it will be trying to unthread that big nut.

 

Fan clutch seems to be OK, nut is tight four days later. I assume the nut wasn't torqued enough after the last repair (water pump, had a shop do it) and the repeated stalling w/o much normal driving, especially due to my multiple tests, eventually broke it free.

Unfortunately, although my wife and I agreed that the truck was running better, it stalled on me twice yesterday after four stall-free days. Coincidentally I was on my way back from the parts store for rivets for our other vehicle.... So, it looks like the CKP wasn't the problem, or at least not all of it.

Troubleshoot plan for tonight is to test the ASD and fuel pump relays. When it stalls, fuel gauge goes dead, so I'm thinking it's failsafe. If relays test OK, will test/swap the CPS-- hope that's easier than the CKP! I'll probably swap the distributor cap while I'm at it. If THAT doesn't fix it, on to the TPS tomorrow.

Matt

 

Yes ! you can back out the screws but the best thing to do is to shim it up like the thickness of a washer.

 

Yes ! you can back out the screws but the best thing to do is to shim it up like the thickness of a washer.

 

Yes ! you can back out the screws but the best thing to do is to shim it up like the thickness of a washer.