DickGiroux

I have a 1998 24Valve...81K Miles. Stock. Stick. Sometimes after a long run, especially if the weather is hot and I back off to an idle (out of gear), the RPM will fluxuate up and down by as much as 100 rpm, fairly rapidly. But sometimes little or none under similiar conditions. . Even when the engine is cold there is a very small movement of the rpm needle at idle. The fuel filter was replaced about 10K Back and I just had the fuel pump replaced. (It's pressure was only 7 psi). The mechanic checked the trouble code (or what ever it is called) and found nothing indicated.

I havn't run it much (no long runs) since the fuel pump was replaced but there is still the very small fluxuation at idle when cold.

Does anyone have a clue what the trouble is and how serious it is in terms of future problems???

PourinDiesel

Its normal.

J BODY

.....normal good...or normal bad? either way...they all do it.

jrs_dodge_diesel

Its normal. The RPM guage gets its reading from the Crankshaft Position Sensor. Its a magnetic type sensor. If your engine RPMs were fluctuatining like that you would definetely hear it.

DickGiroux

In responce to my fluxuating rpm post, several replies suggested that it is normal. One said that if there were a real fluctuation problem it would be heards and not just show up as a rpm needle reading. To clarify this: yes the engine is heard to speed up and slow down just as he needle shows...so that it is a major change in engine speed when the needles moves up and down between about 800 and 900 rpm. Do other owners experience this?

Mopar1973man

No... I don't. I do have the bouncy tach needle but the engine purrs like a kitten. The engine doesn't change rpm... Or at least I don't hear it...