I was hoping someone out there might be able to answer a question I have about a 460 engine?When you start it up everything sounds fine,then after about 3 minutes or so it sounds like it's cutting out for a second.When I get it on the road and gun it,it runs like a champ,very smooth shifting and powerful without any hesitation.As soon as I let off the gas and coast, the engine wants to cut out,almost like a rough idle but only every 5 seconds or so.At idle,it sounds fine then in 5 seconds it gets lower rpm,kinda ruff,but just for a second,then runs good.Anyone have any ideas.Thanks for any help.

 

It kinds of sounds like you have a problem with the IAC (Idle Air Control)

When you let off on the gas pedal, the throttle plates close completely, and the IAC allow air to by-pass the plates, keeping air intake for idle.

There are posts on FTE on cleaning the IAC, which can work, as the "piston" inside the IAC gets build-up, and sticks. Or, just replacing it might solve your problem. Cleaning is the first option, as the IAC runs about $65.

 

Thanks for the reply.Could that still be the problem if It wants to cut out when it is at idle as well,not just when I let off the gas?

 

Yes, possibility, because the throttle plate is closed at idle, and the only air intake is threw the IAC.
If the IAC is dirty or a sticking piston, that would effect air flow threw the IAC.

The other sensor that will effect what your writing about would be the TPS.
That picks up the position of the throttle plate and sends a single to the ECM.

One other problem that wound effect the idle/Stalling would be the EGR valve.

Same as always, It's best to get codes even thought your CEL is not on, as there are codes stored in the ECM, that would send you in the correct direction for diagnosing your problem.