idle problem

[merv m]

the other day i noticed the idle speed was down to 550 it has always been 750 i just changed the oil and fuel filter any ideas thanks merv

 

[Prairie Dog]

My first thought is the FCA on the back of the CP3 (the only thing that has wires coming out of it) is starting to act up. You can add some two stroke synthetic oil to you fuel and see if it quits. If it does then it's probably the FCA.
Or you can just replace it - they're a little over $100.

 

[cerberusiam]

Was the idle actually down or is the cluster dying, that is the first thing to determine. FCA would be a good place to start if you have a lot of miles. Costs a lot less than a cluster.

 

[merv m]

are instrament clusters prone to fail on this truck with 110,000 on the clock

 

[Ozymandias]

Do a cluster check.

 

[cerberusiam]

The mileage is not the issues, being 9 years old is a bigger factor. Electronics can fail at any time, failure rates go up with age. Dropping 200 rpms if idle speed shuld be instantly noticeable in engine tone and sound if you are used to a normal idle. With an FCA problem rarely will it drop and stay at a lower idle, it will idle up and down and that is easy to hear.

First question to answer is does it sound like the idle really dropped that low, or, does it bounce. If it doesn't thne it is back to cluster, CPS, ECU, data bus, and all the harnesses in between.