idle RPMs up & down

[DintDobbs]

@Kidd7 Incidentally, @DemonMudder found that replacing his IAC corrected a similar issue. Consider checking out his thread, specifically post #1042 describing his problem:

-Deathrow Update Log-

Keep going is the goal. I have to fix the pinion bearings in my work Explorer this weekend etc. I don't have a way to rebuild the rear, so I'll be swapping the rear from my Mounty, and the diff's between them. I have a Torsen in my Mounty which has been great for my needs. I don't want to let...

www.explorerforum.com

and post #1074 describing the final solution:

-Deathrow Update Log-

https://www.explorerforum.com/forums/threads/what-are-the-valve-body-torqe-specs-5r55e.180919/reply?quote=1619444 Voila... Thank you so much!

www.explorerforum.com

 

[DemonMudder]

If ya do try the IAC, make sure ya stick with the oem one, anything aftermarket is gonna suck it seems. Make sure they look the same as both my motorcraft ones do in post #1074. Wish ya luck!

 

[Kidd7]

thanks for all the info here, I'll keep ya'll updated.
To clarify this is a 5.0 v8.

 

[DemonMudder]

thanks for all the info here, I'll keep ya'll updated.
To clarify this is a 5.0 v8.

Not a problem, and V6, V8, IAC has the same function and symptoms. So hopefully that's your culprit indeed. But dang lucky on having the V8 lol

 

[Kidd7]

Same function yes, may not be the same part number though.

I will also add that when this occurs (the idle up/down) if I put it in gear she'll settle down. Not sure if the load on the engine changes things or if the ECU / sensors act differently at that point.

Thinking on this more: when this does happen and it's ~1k RPM swings, if I give it some gas and bring the RPMs up to say 2k it will still bounce up/down. That tells me it's not a TPS issue.

 

[Kidd7]

Finally got the new IAC installed, will monitor and report back.

 

[Kidd7]

Now that the new IAC has been installed for a while, I have noticed there is a slight RPM bounce when warming up. No where near as bad as it was, maybe a couple hundred RPM difference. Haven't experienced any issues while driving or after warm up.

 

[amj441]

Now that the new IAC has been installed for a while, I have noticed there is a slight RPM bounce when warming up. No where near as bad as it was, maybe a couple hundred RPM difference. Haven't experienced any issues while driving or after warm up.

is that when you have the ac on? could be the compressor kicking on and off

 

[Kidd7]

Very possible, this rig has the automatic HVAC. I'll have to pay attention to that and turn it off to try it out.

 

[Kidd7]

A couple times now I've made it a point to turn off the HVAC and idle is smooth.