Engine/Transmission (1994 - 1998) RPM changes in my 12 valve engine at idle question.

[HerbW]

Hi. One more question while I'm typing.
My CTD 12 valve changed RPMs at idle all the time. Is this due to weak return springs on the throttle? This is after being warm and not the cycle after cold starting. I know the AC with alter this but this is normal time without AC or defrost in use. It can be as low as 675 and up to 900 RPMS while in drive. The small spring that's about six inches long to the pump broke last year and I fixed the one broken end and seems fine. There is a longer and stronger spring by it that put the linkage pretty tight on the 6MM adjustment screw.
thanks, Herb

 

[Bob4x4]

idle speed is controlled by the governor not any return springs.Low fuel pressure can have an effect as well

 

[fest3er]

Does the RPM change by itself? Or is the idle speed constant when it returns to idle, but different each time?

If the former, it's probably governor springs. If the latter (and you know you don't have frayed cables), the linkage shaft (bottom/rear of p-pump) may sticking; lots of PB Blaster, work it free, then lots of oil to lube it. After 10-12 years, mine had started to stick; I done did that and it's been fine since.

 

[GAmes]

Although I don't believe the springs would cause RPM fluctuation, this is what the springs on your lower linkage should look like, except both springs will be the same size. One of mine is larger because I have a Jacob's exhaust brake.