97 3.0L rough idle

[Georgia Boy]

Help!!! I bought this truck about a month ago (98,000 mls on the odometer) and it ran perfect. Know it has a rough idle especially when the a/c is on and it has a very high idle at start up and when you press the gas pedal and release it takes a bit for the idle to slow. The idle does smooth out a little once the engine warms up but it does not completely go away. I am in the middle of replacing the plugs and wires. So far all the plugs look good except #6. It has carbon build up only on one side of the electrode. If the plugs and wires don't help I am going to replace the coil. Any suggestions would be much appreciated.

 

[RonD]

Use motorcraft wires and plugs, and use double platinum plugs if you want longer life.

All fuel injected engines use an IAC(idle air control) valve to set idle RPMs.
Idle screw can't work because there are no jets to suck extra fuel from using a choke plate.
When you start the engine the computer will open up the IAC valve all the way, so without touching the gas pedal, the engine should rev up to 1,500+ RPMs then start dropping down to match engine temp
Cold engine should idle at 1,100 or higher, depending on outside temp, colder = high
Computer will then slowly close IAC Valve as engine/coolant temp goes up, pressing on the gas pedal doesn't change this, there is no Choke Plate so no idle screw cam and spring to reset by pressing gas pedal.

When engine temp reaches "normal" the idle should be 600-650 for manual trans, 700-750 for automatic

If new wires and plugs don't completely solve the issue then try a can of Seafoam or similar injector cleaner in the gas tank.
Fuel injector tips will get dirty over time, and drip fuel instead of spraying it, this can cause idle misfires and carbon build up.
I use cleaner once a year on all my fuel injected engines, smooths out the idle.

 

[Georgia Boy]

Thanks Ron
The plugs and wires did the trick. Idles smooth now.
I have a new problem know. I am getting a squealing sound from the passenger side of the engine up next to the firewall. From what I've read it sounds like the camshaft synchronizer is the culprit. I took a piece of hose and pin pointed that the sound is coming from that area. It looks like it's going to be fun to change out since I can't even see it.

 

[RonD]

Yes, that description of the sound and location would be synchronizer.

Good read in the tech section: http://www.therangerstation.com/tech_library/index.shtml

Look in the Engines & Fuel area

 

[holyford86]

If the synchronizer is making noise, don't drive it until you replace it, the engine will still run with the gear teeth stripped off and it won't have oil pressure. I've seen two motors destroyed in that manner