My 91 F-150 4.9L starts but idles extremely rough and stalls unless I hold about a quarter pedal down.
It's done this about 10-12 times over the year, but once I shut it off and re-start it it would be fine.
It was completely normal just a couple of days before I last drove it.
Will a MAP sensor act up then eventually die? Or do they just die without warning?
Thanks!

 

The MAP sensor seems to be a pretty reliable unit, don't know of anyone who has had one fail - not that they haven't failed, just seems to be really rare. Would check that the vacuum line between it and the intake manifold is in good shape, though.

Mine used to do what you describe - especially bad during cold weather starts or sitting overnight or for extended periods. My workaround was to roll the ignition key to On a couple of times to let the fuel pumps fully charge the system, then roll on over to Start. Suspected a failed check valve or the like, never looked into it any further.

 

It did end up being the MAP sensor after all. So my question is answered, YES the MAP sensor can show early signs of falure.
I did however change the TPS and IAC at the same time in that order, hoping it would be one of those and I could return an unused part or two. But, it didn't work out that way and I'm fine with having them replaced anyway.

 

So did you replace the MAP then test, then replace the other two? If you replaced all three at the same time then there's no way to know which one fixed the issue.

 

I just wrote it wrong, I changed them one at a time, tried it each time. It ended up being the MAP.