I have an '05 V8 Limited with 217k on it. Both valve covers were weeping pretty badly so I finally got around to swapping out the valve cover gaskets yesterday and replaced the spark plugs while I was at it.

I did the passenger side in the morning and test drove it a couple of miles. Everything seemed fine, I didn't notice any issues.

Then in evening I did the driver side. After I put everything back together and started it up, it was idling very slow, about 500 RPM or less where it normally idles quite fast, 900-1100 rpm. It was also producing a LOT of white exhaust.

The idle is smooth despite being so low, and while I didn't try flooring it, the power delivery seems pretty normal too.

It was late by then and I had some family stuff to do this morning so I didn't have a chance to try to sort it out, but I'm looking for suggestions what to look for when I do have time to troubleshoot later today.

Edited to add it's the 4.7 V8

Thanks in advance!

I forgot to mention that my plan is to start by pulling the plugs and having a look at them, but I wanted to know if anyone had experienced a similar problem and had a better suggestion from experience.

I would drive it a little bit to see if the issues clear up before doing anything else, and if not check and make sure all wiring is connected properly, then move on to checking the plugs.

It maybe the computer is just readjusting itself after the work you've done, especially if you disconnected the battery.

Thanks for the suggestion, I might give that a shot since I need to run to the store. I did disconnect the battery for both work sessions.

Low idle RPM can be explained by a disconnected battery if your throttle body is dirty. But, white smoke can't. Try to get a good whiff of it, does it smell like burning oil or coolant?

Thanks all for reading, and thanks again for the suggestion to just drive it, @AuSeeker !

I drove about 20 miles, maybe half on the highway at 75-80 mph, and all seems well now.

It was still idling at very low rpm when I started, but now it’s just a little lower than I remember it being.

I also pulled over and did this during the drive, no idea whether it contributed. (Found on a Tundra forum.)
I think the exhaust concern was a combination of normal winter condensation and having the truck parked in an unusual location while I worked on it. That caused the outdoor lights to really accentuate that condensation when I started it, on top of me being tired because it was late and I’d spent much of the day out in the cold garage leaning over the engine bay.

I’m really glad it worked out. The shop wanted $1000 to do the gaskets plus another $100 to do the spark plugs, and my parts cost was well under $100. I really didn’t want to pay that for such a straightforward job. That’s not that much less than I paid to have the timing belt replaced!

Thanks for the follow up, many come here for help but never follow up if they solved their issues, you following up WILL help others in the future who may have a similar issue/s.

Also thanks for posting the Throttle Position Reset procedure, that also will help many in the future!!

Heh heh, yeah, as an active member of several work-related (IT) forums, I hate to see that.

This isn't quite the same thing, but it's what I think of:

After my battery went dead my 05 4runner we gave it a jump start but was idling, while waiting for the battery I had replaced the sparkplugs and serpentine belt but wouldn't pass 500 rpms. I watched a video that says how to reset the idling memory. I was surprised... I had to turn the ignition on but do not crank the engine. DO THIS 3x then turn the engine on, engage the emergency foot break all the way and put shift on drive and leave it until it regulates. The video said 7-8 minutes. The firstvtrird it turned off. I repeated it and left it running for probably 25-30 min. You don't have to do anything else. I noticed how the engine was regulating.. I am very proud to have fix it. My 4runner is running beautifly again! Hope this helps.

That's a cool bit of info.