2004
4.6l V8
50,000 miles

My engine has a wild idle recently. It will go anywhere from 500ish to 900ish and fluctuate between the two very fast. Almost in a cyclic manner. I don't know what the deal is. When I'm on the gas, its ok, but when I slow down to idle speed it starts going crazy. It has died a few times on me while slowing down below 5 mph. The throttle response seems laggy also. Today the emissions light came on. This all started about 4 days ago. After doing some reading, I think the throttle body needs to be cleaned..? But does 50,000 miles seem too soon? Any help would be appreciated Thanks!

 

clean the throttle body and the idle air control valve. You may just want to replace the iac.

 

I don't think the 04 has a IAC, it's electronic throttle.

Go get your codes read. Autozone does it free. Post back with the exact codes, not what the clowns there tell you what they mean.

 

Ok I went to autozone and they plugged up the computer, but my truck wouldn't register with the computer. Uh oh!? So I bought some STP Throttle body and air intake cleaner, and just got done doing that. There was a lot of black gunk behind the flap and it seemed to get rid of most of it. I wiped a lot of it out. The engine is idling much smoother surprisingly.

 

yea cleaning the throttle plate seems to help the newer 04+ trucks. good job . did you clean only the throttle plate or the whole throttle body?

 

Nah I cleaned the whole inside too. I just sprayed that stuff in there, I didnt take the throttle body off. Don't worry! It's still running haha. Ok I replaced a fuse and the diagnostics computer could connect. Much smaller problem than I expected. Ok here are the codes:

The PCM has determined that the engine RPM is lower than expected for the current engine operating conditions.

Definition:
IAC Circuit Condition or Idle Speed Higher/Lower Than Expected

Explanation:
The ECM has detected that the IAC counts are higher or lower than expected, the engine speed is not in its expected range.

Probable Causes:
1. Vacuum leak on engine
2. Dirty Throttle Body
3. IAC motor defective
4. Poor Electrical connection to IAC valve

 

disconnect the battery to clear the codes if they havent already been cleared. then see if they come back. you dont have an iac. alot of times cleaning the throttle plate seems to fix that code from what other thread starters say. not sure about cleaning the whole tb but i'd think it'd have a better effect.

 

Sounds like the computer needs to re learn it's idle again.

Disconnect the battery, leave it disconnected for about 15 minutes.

When you restart it, don't touch the gas pedal for several minutes. Reset your radio stations or something, but leave the throttle alone. The idle may go up and down during this time as well, but it 'should' even out after a couple of minutes..

Hopefully, that will fix up your idle...

And if not, well, it was free and only cost you some time....

Good luck!

Mitch

 

Do you remember the code #'s Noah. I think the 04 models require controller area network(CAN) protocol . ? Well, there's one recall that I know of, quite a few TSB's in the links below.

I know people have gone to great lengths trying to fix that problem. Some have succeded tho.... - After the dealership changed the motor mounts, reflashed the PCM and neutralized the engine. I read that some people had to take it in for a reflash twice.. Hope you don't have to go thru all that.

Special attention to the TSB's and recall info. Just make sure the 4.6L is listed. Both 5.4L /4.6L' s were going in for the reflash for a time. It wasn't just a 3V prob.

Personally, I would put some Motorcraft Fine Wires in there first, but, that's up to you... Oh, and don't let Mitch talk you into Botch +4's (4= Four times as bad.)

http://www.ford-trucks.com/tsb/fullt...hp?tsb=05-5-15

http://www.aboutautomobile.com/tsb/2004/FORD/F150

Good Luck man.

 

It is amazing how much crap is in the fuel these days. I clean my throttle body on my truck and the wife's car almost every couple of months and inspect them each month. Everytime I clean them they are black...

 

Or 4 times the mileage you'll get out of a set of plugs! ha, ha!

My idle is still rock smooth and is smooth as silk pulling 3500 rpms in second gear hauling the TT up a 6% grade with only about half throttle at 55 mph... Oh, and these plugs have over 120,000 miles on them now! ha, ha!

It's been awhile for the plug jab jbrew, so I'd thought I'd just go along with it too!

Mitch

 

Thanks for everyone's help. I needed it. And about the plugs, I just bought some two weeks ago! I just got the Ford recommended Motocrafts. I dont know much about them does anyone have a link to a write up on changing them? This will be my first time changing plugs. I have a buddy who knows what hes doing, but I would just like to know what to expect.
Again, thanks for everyone's help!

 

dont forget the dielectric grease in the boots of each cop. that is one of the biggest things that people forget and their engines dont run right.

 

Matt, he has a 4.6. Those are straightforward.

Gotta read a bit more carefully!

 

Save those plugs Mitch, -Collectors Items. Bosch only made 8 good spark plugs. You cornered the market buddy..