idle surge in drive only

[rtbrjason]

Started noticing this issue after a bunch of work, so not sure if it is related or just something else that popped up.

Car idles fine in Park. When in drive and stopped with foot on brake, I'm getting a bit of a rough idle and barely noticeable surging. The rpms aren't surging so much, it's more a surge of poor idle. Once shifted into park it is fine.

I cleaned EGR/IAC. In the case of the IAC, I dropped the new gasket down into engine abyss and had to reuse the old. This could be the whole issues I guess. I replaced all plugs/cops. PCV valve replaced. TB removed and fully cleaned. Upper intake was fully cleaned at that time. Most of the vacuum line system has been replaced at this point as well as I found several small leaks or shot pieces of tubing.

The only similar post I've found was on the other Ford forum, and for a Bronco with a 5.8. He was having the same issues and solved it with a fuel pressure regulator. Anyone else have this issue and solve it? Would that be a good place to start? I don't have a fuel pressure gauge to check it with unfortunately.

 

[gaping46and2]

Did you replace the IAC, or just clean it? Any codes?

I had some of the same symptoms you're describing and had a CEL related to the IAC. I cleaned it, and still had issues. Then replaced it, and the idle has been normal since.

 

[rtbrjason]

I did not replace it. I pulled it out, cleaned with b12 chemtool spray and went to put it back on with a new gasket. While installing, the gasket slipped down and could not be found so the original gasket had to be reused. So this could all be relative to a leak there I guess, or maybe I screwed up the IAC while cleaning it.

Is this one of those parts that people would suggest a motorcraft replacement for or will anything do?

 

[gaping46and2]

I replaced mine with a duralast part from autozone. I don't know if it's entirely necessary to spend 2-3 times as much to go with the motorcraft part.

 

[rtbrjason]

Just to follow up this post, I ended up resolving this. The truck was getting to be tough to start and with the remote starter it would always take 2 cycles. With the key if you cranked it initially it wouldn't want to start but then the next crank it would start right up. I ended up replacing the whole fuel pump/sender assembly and the idle is nice and smooth. Apparently the pump/sender wasn't holding pressure anymore.

This cost a bit more than I wanted to spend but I felt like I had to go with a motor craft part since this job isn't exactly easy to do. The pump/sender was close to $300 shipped.