Runs Rough on Cold Start-Up

I have a 1998 Ford Windstar. I recently replaced all of the intake manifold gaskets (upper and lower), EGR valve, spark plugs, spark plug wires, and PCV valve. Now, when it sits overnight and is started for the first time in the morning, it revs way up (2K), then drops way down (500) and runs very rough. Then it will rev back up to 2k, then drop back down. It will do that maybe three times, then quit. If I hold the gas pedal at 1500 rpms for a minute or two, then it is fine; and will run fine the rest of the day. Any ideas?

vacuum leak, IAC AND MAF. Make sure that all hoses are connected properly. Check that you plugged the MAF "mass air flow" and IAC "Idle Air Control " back in..


Do you have any DTC set?

well, vac leaks are always the suspect but if you say that after it's gone thru the warm up period it's fine, I'd be more inclined to look at your IAC. I'd be of the impression that if you have a vac leak that all of a sudden goes away, only to resurface when cold again, it likely isn't a vac leak..

well, vac leaks are always the suspect but if you say that after it's gone thru the warm up period it's fine, I'd be more inclined to look at your IAC. I'd be of the impression that if you have a vac leak that all of a sudden goes away, only to resurface when cold again, it likely isn't a vac leak..


Don't count the vac out just yet. Cold engine needs more fuel less air. Hot engine needs more air less fuel.

No check engine light. No other issues at all other than just the first few minutes of a cold start-up. I was thinking vacuum too, but I have looked and looked. I have never had an issue with IAC before; when I had it off and replaced the gasket for it, it actually looked pretty clean inside. Thanks for the input everyone, I appreciate it.

When the engine is running and you unplug the IAC you should see a difference in how it runs.

Here is a quick easy way to check for big vac leaks.
http://www.youtube.com/watch?feature=player_detailpage&v=zMok2y05jNE