I have a 2004 with the 5.4L and after the engine is warmed to operating temp, when I am sitting at a red light with the truck in gear, my rpm readout is between the 500 and 750 marks on my tach. I have been trying to figure out this slight rough idle under the condition above, and I have just about come to the conclusion that 625 rpm's is just too low. All I can figure is the PCM is telling the engine to idle at 625. When I manipulate it to 750, all is smooth. Do any of you have the same situation? Does anyone else agree that my rpm's are too low. I have done everything I can think of such as change out plugs and COP's, cleaned MAF sensor, cleaned throttle body, new clean air filter, etc. The only thing I haven't checked is for a vacuum leak, but I don't think that is the problem. Is there any way short of buying a programmer that I can adjust the rpm's up enough to get rid of this slightly rough idle when stopped and in gear? Is there a specific rpm the engine should be under this condition?

 

Dunno whut happened to my post - be here it is again.

That's normal rpm.

programmer bump will just be masking the root cause.

-vac leak
-failing front O2's
-exhaust leak before front O2's
-intake leak (unmetered air)
-injector(s)
-Bad TB
-bad MAF
-VCT system (causing timing drift)


Which COPS and plugs did you use ( just curious)

Any stored codes?

good luck

MGD

 

No stored codes. I used the updated Motorcraft plugs (715?) and Accel COP's (the yellow ones) I also have the updated VCT solenoids.

Thanks for the troubleshoot list.

 

Probably the Accel cops, they are garbage.

 

Actually, I had the slight rough idle before I changed out the COP's. They didn't stop it.
Any other ideas?

 

I had a rough idle for a while and the culprit turned out to be the throttle body needing to be cleaned. When was the last time you did that?

 

2 weeks ago. Took it off and bench cleaned it with CRC throttle body cleaner. I'm thinking about changing out my O2 sensors even though I am not getting a DTC. Does that make sense?

 

How many miles on them?

 

If they are 2004 originals with at least 80k+ on them, it would be prudent just from a maintenance perspective to maintain peak efficiency.

Ford's O2 DTC threshholds have more to do with their TCO than actual component health. Yeah - they may still work, with lazy switchrates and slow heating, but not very well. To me they are consumables and have always been part of my regularly scheduled preventative maintenance regime. ( I'm also the nutjob who R&R's plugs every 30K , lol)

O2's have also been known to fail ( although rarely - they usually just degrade slowly with use ).

If you have access to some sort of datalogging equipment; tuner ( e.g SCT and Livelink), Autotap/with interface, etc, you can log and compare/examine the characteristics of the left and right front O2's. This can help determine of they are healthy.

If you do end up changing them, try to use Motorcraft replacements if you can.

MGD

 

Truck has 166k on it glc. MGDfan, yes they are the original ones. Guess it's time to get out the Haynes and buy one of those gadgets specifically for removing the sensors. Any advice on which one to get? Also, thanks for the insight. I always check on MC parts first and usually get them if folks on the forums are obdurate about them, and Ford has improved them (no doubt there are plenty of parts on these 5.4L 3 valve engines that needed to be redesigned).

 

The needed socket should be in most parts store loaner kits.

 

Hi.

This should help: https://www.f150online.com/forums/ar...r-install.html

'Obdurate', eh? Hell fahr, yall MUST be frum Tenn'see!!! Yer the only uth'r feller ah knows whut has a fayncy vobabulary like thet! That other feller be ol' Bubber hisseff - Big D, outt'r Knoxvegas!

Best of luck!

 

LMELHSAO!!!

'Ell I be dern! Ah figger'd me 'n Bubber's awl alone inna F-one-fiddy world o' fayncy writin' words 'n sich. Looky thar, Maw! A feller coon-sewer!

Ever-dently, cipher'n hain't tha only thang 'is hyur feller's a whiz at.

I tip my hat to you, sir.

 

I've removed my O2 sensors several times just with a wrench and still see no reason for a special tool. Maybe if they're rusty? I've yet to see a compelling argument for using the special tool.

 

He's talking about the O2 sensors, not the plugs..................

The tool makes it a lot easier and it should be a free loan.