Hi, my 98 4.2 starts right up in the morning and runs fine all day. The only issue is when I park it somewhere for a bit (say, a typical Home Depot run) and then go to restart it. It starts right up, but it stumbles and runs rough for 30 secs or so and then it's fine again. No codes.

It almost seems like vapor lock, but I don't think it's likely with electric pump in rear, also I have been through 7 hot Fla summers with this truck and it never gave me a problem til now.

Has anyone experienced this? Appreciate any input.

 

Hard to say for sure, but some things come to mind....

Plug wires
Idle Air Control
MAF
and possibly a vacuum leak.

Plug wires can cause all kind of oddball stumble, rough idle, etc. It'd be worth replacing them if the are old. (I only use Motorcraft. Other wires have given mixed result for guys here over the years)

Let us know when you get it figured out. And you will

 

+1 on checking the wires. We replaced them on our 99 with Motorcraft wires and the difference was evident!

I just wish ours didn't stumble so much when leaving a light.

 

+1 on checking the wires. We replaced them on our 99 with Motorcraft wires and the difference was evident!

I just wish ours didn't stumble so much when leaving a light.