99 Explorer wont start

[Free89broncoii]

Ok.... I bought this Explorer about 3 months ago. Its been running great.. once the weather started to get cold there would be some mornings that she would start right up, others not so much luck.

I started by replacing the IAC valve... problem still continued. She popped a check engine light .. codes 171 and 174. After the reading that I have done it seems that the SOHC 4.0 has a known problem with the intake gaskets. Tore her apart and replaced those.... checked all lines in the process to make sure there was no vacuum leaks. I used the Actron OBDII reader and reset the codes.

For the past 2 weeks she has been running great. Starts every time.... all the sudden today I get a call. Girlfriend is stuck... the Explorer wont start. Drove out and picked her up... tried for about 5 mins and no luck. Now I just got home from work. I went out and checked to make sure I could hear the fuel pump and she is making the noise she should be. Reach in and turn the key and she fires right up. No codes.... I need help badly on this.

What are the next steps I should try?

[Free89broncoii]

Probably not related but I'm going to ask anyway.

On my BII.. we were on a wheeling trip. I had serious problems with intermittent starting. In the end it was found to be an inertia switch that seemed to be going bad. Not the best idea but I bypassed the switch and never had a problem again. Any chance this could be the problem?

[rtg143]

If you bypassed the inertia with good connections, that wouldn't cause the no start, but I'd get a used one from a salvage yard and install it. All Fords should be the same part. The way I'd check it is when it won't start, listen for the pump. It may be on it's way out. If it runs but the truck won't start, check for spark. If the pump runs and you have spark, shoot some carb cleaner in the intake and see if it starts.