Engine won't start when warm after installing BBK Underdrive Pulleys
 

I have a 2002 F-150 4.6 V8 and recently had the BBK underdrive pulleys put on by a local shop. The truck runs fine and starts right up when the engine is cold. After driving the truck around and the engine gets warm, the engine won't start up again unless I rev the engine a bit. Very strange issue and was wondering if anyone else has had this issue?

So are you saying it cranks excessively before starting after the engine has been warmed up and shut down, or are you saying it idles very low and requires the gas pedal to stay running?

Did you pull any codes?

It doesn't crank excessively and turns over like it should but does idle very low and require me to put my foot in the gas and rev it up for a bit so it will stay running. It runs just fine after I rev it up a bit and the engine gets going.

I don't have a code reader at the moment but can run it up to Autozone and see if there are any codes being thrown if you think that would help. There is no check engine light when it's up and running.

Sounds like the Intake Air controller is not working.
It is the sole control of idle.
Good luck.

Not sure if it matters but I do have an aftermarket CAI on it as well and it's been fine for the last 6 months. The UDPs were put on last week and ever since have had the warm start issue. Are you referring to the IAC valve that might be bad?

Yes. IAC= Intake Air Control.
Good luck.

Gotcha. I was thinking the truck might need a custom tune in order to fix it and/or take advantage of the upgrades. I'll start with the IAC valve and work my way from there.

I don't think the IAC has ever been replaced so it will probably need it soon anyway. I've got 112,000 miles on it.

Also clean the MAF, especially if you are using an oiled air filter.

Thanks everyone. I'll start troubleshooting it this weekend and let you all know how it turns out.

The shop might have moved the air inlet tubing out of the way to install the pulley(s). Look for a leak in that area and or improperly connected connectors,