Recently replaced the alternator and battery on my 2004 Ford F150 4.6 XLT. However having done that the engine light has come on and when idle I get low RPM.



Only things removed to get to old alternator was a radiator hose and air intake pipe. Intake was clean and coolant fluid was replaced. Tried to check as many cables, etc. to see if anything got loosened or knocked out of place but haven't come up with anything.

Took down to AutoZone(2 of them) to get the battery/alt/starter tested after doing the work and everything checked out. When they checked the engine light code (506) they come up with this:



Anyone have any other thoughts before I take this in to get checked out?

Edit: Could be mistaken but I think gas mileage has taken a hit

[This message has been edited by chipotle (edited 8/10/2013 2:03p).]

New body style F150 or Heritage?

If new body style, check to make sure they reconnected all the vacuum hoses correctly, then go buy some blue shop towels and a can of 3M throttle body cleaner.

Take the tube off going to the throttle body and look inside the metal part, bet its gunked up.

Put paper towels down below the opening as it will drip.

Use a long screwdriver and push the bottom half of the tb door, it pivots in the middle.

Use your cleaner and hose it down good, while keeping the door open. Then use a paper towel and wipe down whatever you can with it, It will be gunky and black.

Put it back togehter and start it, note it will probably not want to start, or stumble at first (from all that TB Cleaner), but keep trying and rev it a few times, and it should smooth out within a few minutes.

Also recommend you go buy a acan of Chemtool B12 and drop it in the fuel tank.

Good luck.


EDIT:

once you do this, disconnect the negative terminal for 20 minutes to clear the keep alive memory. And then reconnect it (good time to buy those felt washers if you havent for the battery).

Start the truck, idle in park for one minute, no AC.

Put it in drive, foot on the brake, 1 minute.

Back in park, turn AC on, 1 minute, Put it in drive, AC on, foot on brake, 1 minute.

Then drive it like you normally do so it can 'learn'.

[This message has been edited by 1agswitchin4lanes (edited 8/10/2013 6:11p).]

appreciate the help

Cleaned out the throttle body. Didn't appear to need much work. So far so good on the idle and doesn't feel like it's going to stall out.

Your edit helped on the engine light. Can you explain what that part accomplished?

Again. Thankyou.

your truck is DBW = Drive By wire.

Ford eliminated the Idle Control Valve when they went to DBW, since you can command the PCM to take teh DBW module mimic Idle Air COmmands.

Over time, from the truck being new, intake deposits and oil will form on the throttle plate, and the truck may not be able to maintain the exact RPM command as before, so the PCM will 'learn' to open the DBW plate more to compensate to maintain specific range.

Well, when you replaced the alternator, the PCM lost memory, so all it knows is to open the plate to the same area when the truck was brand new. Not after 9 years of oil and grease and sludge from PCV air. So by cleaning and resetting the PCM, and doing the idle park/drive; Park /drive with the AC on, the PCM re-learns the functions over again, so it can maintain the 'new' normal.

That's what I needed. Thanks again for your help.