99 explorer 4.0 automatic, lately been running weird. Starts up but will stall out unless you let it warm up. And idle drops below 500 rpm. And is really rough feeling. To like 2 or 300 rpm, then will stall but will start right back up. When I changed spark plugs and wires problem stopped for about 2 weeks and now is back. And has no engine code. Any help would be greatly appreciated it!

 

Two ideas: Dirty throttle body valve or idle air contol valve (IAC).
Wouldnt explain the improvement with new plugs and wires though.

 

Did you disconnect anything else in the process of installing the new plugs and wires, such as the intake air tube or MAF sensor? If either of those were not installed correctly (allowing unmetered air in to the intake) it could easily cause what you describe.

Also, double check your spark plug wire connections. It's pretty easy to not get one fully seated and cause a misfire. After enough engine run time it should trigger a misfire diagnostic code, but you may not have run the engine long enough to set such a code yet. I'm not suggesting you drive the truck for a few days to set a code since doing so would be hard on your catalytic converters. Start by carefully inspecting all vacuum hoses, spark plug wires, and air intake connections for issues.

-Rod

 

Sounds like one of the many problems I chased for quite a while.
Refer to my post titled - New Life For An Old Explorer

 

I will check the TB and IAC. And it was having the same issue before spark plugs were changed. And explorerjwd I couldnt find your post about New life to an old explorer. Im not used to the explorer motors lol I look at my f150 and know right were everything is, ill have to dedicate a day to getting used to the 4.0

 

Search the Forums with New Life For An Old Explorer in quotes.

 

It could be the DPFE which was a common issue on the earlier Fords, but they often would set one or more diagnostic codes.

-Rod

 

There may be many reasons. It can be extra air being sucked in from some hole or disconnected air pipe. Or you could also check fuel pressure. And it's also posible that it's idle control valve. But not always. I had problems with idle on my OHV 4.0, turned out to be a loose connection of the EGR pipe which sucked in extra air.