Ford Repair: Hard starting, upper intake manifold, air control valve

Question
Hi Dave,
  I have a 2000 Ford Ranger 4 cyl. (102200 miles) It is hard to start when cold. If I hold my foot about 1/2 down on the gas it will start and run as long as I keep my foot on the gas until it warms up.It runs fine once it is warmed up. Another problem I have is it pings under load. It will run fine at crusing speed until I go up  a hill then it starts pinging. I have had the plugs replaced, new Ford plug wires, new gas filter, and all the dianostic codes check out O. K. Any suggestions?
  Thank You, John

Answer
When starting the engine and at idle, the throttle plate is closed and the only air entering the engine is through the Idle Air Control Valve (IAC). This is all controlled by the Powertrain Contol Module. It uses the IAC to allow a small amount of air to enter the engine for starting and to adjust idle speed. The IAC is mounted to the upper intake manifold with two small bolts, and has a small electrical connector on it. It is about two by four inches. It may be sticking closed, you can remove it (be careful, it may have a paper gasket) and clean it out with an Air Intake Cleaner. If this doesn't help, it may have failed and need replacing.

As for the pinging noise, I would guess that this is Detonation (Spark Knock).  It is probably caused by a carbon build-up in the engine.  Spark Knock is very bad for an engine, it can actually damage the pistons.  You could try using a higher octane fuel, this will lessen or eliminate the pinging, but it will not remove the cause of the problem, the carbon.

This is a passage from the service manual for removing carbon in an engine.

"The recommended drive cycle should include daily periods of engine operation above 3,000 RPM, such as a brisk acceleration from a stop position. This will break/burn the carbon off the piston head."

Carbon can be removed by a pouring a special liquid into the intake through a vacuum hose while the engine is hot and at running at idle.  This can be dangerous, it could lock-up and destroy an engine if done wrong.  I would recommend taking the vehicle to a Dealer for this service.

I hope this helps,
Dave