Hey gents,

My truck has been acting a bit weird lately. It's doing 2 things that concern me.

1) If I drive the truck for a while, then shut it down, then try to restart, it starts very rough. Kind of hard to explain. In the mornings however, at first startup, it starts smoothly.

2) After driving for an extended period, say about 15 miles, upon reaching a stop light and coming to a complete stop, the idle dips down below 500 then pops up to normal.

My truck is a 2001 Expy 4.6. About 65k miles on it. Plugs are pretty new. All coils are new. No CEL light. Any thoughs are much appreciated.

Tony

 

Any mods?

 

Have you tried injector cleaner, or replacing the fuel filter? I don't know if that will do it, but it too sounds like a vacuum leak. I've cleaned things when I thaught it was running stupid, like the t-body and IAC, and as far as plugs go, I changed mine at 150 000 km's around. I've had this before, but it never has repeated so?????

 

No mods. Bone stock.

Fuel filter has less than 10k miles on it. Both IAC and TB are sparkling clean. Have also tried seafoam in the tank.

It's got me stumped.

 

Sounds to me like a vacuum leak.

 

vacume leak or the MAF... but most likely a vacume leak. check PCV valve

 

Also check where the pcv valve hose hooks into the upper intake. That hose is famous for rotting off.