If you take the map off, it will never go into closed loop.

Reset the PCM, see if that doesn't improve its attitude. (to echo GD.... )

 

No I did not take the battery cables off when I swapped out the IAC. Is that bad? If it's just a matter of taking the cable off, I'll be happy.

 

Took off cables, no dice. Heard a rattling noise though while it was running, and found it to be from the PCV valve hose. Took off the PCV valve hose from the intake and whattya know, it stays on. Idles higher, around 1000 RPM. If you try to put the PCV hose back on, it shuts off. Could something this simple be the problem???

 

Do you take the hose off, and leave it open? If so, you are introducing a vacuum leak.... and the engine will idle higher....

Did you clean out the throttle body when you changed the IAC? I would be tempted to yank the TB, clean it out real good, (leave battery disconnected while you are doing so.) put it back on, and see if it doesn't wanna work a bit better.

 

And get a new pcv from the dealer.

 

Got a new pcv valve, hose, breather filter (b/c) it was dirty, and now I have the same problem I had before. The engine turn over at a normal speed but not catch! I think it may be time to take it to a shop to do a real diagnostic scan to see if I have a short somewhere because this has got to be electrical.

 

Without having to look back through the thread, you have tried unscrewing the precat o2 correct?

 

So I took off the crank sensor and guess what, it had a split in it. Went to autozone, got a new one, put it on (what a bear of a job) and it started right up. Ran fine for two days with no symptoms, and then shut off yesterday as I was leaving work. Same problem again. Shuts off after about ten to twenty seconds of running and will crank but not catch after it dies. Sometimes it will catch, but then dies again. Could I have gotten a bad crank sensor, or should I be looking elsewhere? I will try unscrewing the precat o2 sensor as zman suggested, but while it's running, it runs like a dream. Will also check CKPS wires, though I thought they looked all right before. BTW, had fuel tester hooked up after it died and read a constant 40 psi, which is what pump is rated to produce.

 

Put your truck info in your sig, and profile please.

Autozone crank sensor? Hhhmmm....... I won't buy electrical parts from AZ. Not after having to replace the same part three times in as many weeks..... What brand sensor did you get?

 

Duralast, ouch.