SmokeyBear

I drive about 25 miles to work 1 way. by the time i get to work and find a spot and put it in park the engine idles at about 925-950 rpms (kinda shakes the whole truck a lil bit). but when i turn the A/C it drops to about 900 even and idles smooth. when i leave work the truck starts right up and idles great but when i get home and put it in park the idles is right back to acting goofy. any advice on what to look for would be awsome. Thanks in advance

jrs_dodge_diesel

RPM's sound kinda high. Should be around 800, 700-750 in gear (automatic). When my A/C kicks in the RPMs don't change, they stay constant.

Please fill out you signature so we know what you have. Lots of variations as the years went by in the Ram lineup.

SmokeyBear

filled out my sig but it isnt showing up srry.
it is a 99 2500 4X4 auto trans 125k miles

jrs_dodge_diesel

Odd, i figurewd this might affect an older 12V more but a 24V? This is puzzling, with the high idle and jumpy RPMs. Wonder if this could indicate a problem with your VP44 (injection pump). How does your truck run other wise?

SmokeyBear

truck seems to run flawless except for this idle problem

str86

SmokeyBear. I have been to the Cummins tech, Dodge, Autozone.... No diagnoses yet. This has been going on for about 2 years. The only constant, the OAT is in the 80's. All else is intermittent. Turn on the a/c and is smooths it out, but not always. Doesn't matter how far the truck is driven. I haven't had it happen in over a month. It did it yesterday morning on the way to work and on the way home. Mixed city/highway driving. Drives me nuts.

Sorry not much help, but you are not alone.

killfast1

Could this be a symptom the the crank/cam position sensor?

str86

Killfast1,

It's possible. I replaced both of these sensors about 3 years ago. It ended up being the crank position sensor that was bad. I lost the tach. The only sensors I haven't replaced are oil pressure, water temp & APPS. I have done the APPS reset.

SmokeyBear

did replacing the crank posistion senser help the idle problem at all whe you replaced it str86?

neveragain

Yours could be due to bad voltage. even with good alternator and batteries. Probably can't but get it checked with and oscilloscope. Make a pin to be able to puncture the wires to see what the voltages are. My condolences for the bad voltages screwup the fuel timing and delivery and make the fuel shut off .

str86

SmokeyBear,

When I lost the tach I replaced the Cam & Crank Position Sensor. Replaced the Cam Position Sensor first, easier to get to, it did not solve the problem. Replaced the Crank Position Sensor & got the tach back. At that time I did not have the rough idle problem. One of these days I will track it down. I have a spare Cam Position Sensor. If I have some time today.......

SmokeyBear

Just a thought but would a hole in the intercooler boots cause this or a bad seal somewere on the boots?

SmokeyBear

replaced fuel filter, it was pretty dirty. engine runs smoother sounds stronger but didnt chcange idle problem any

AAmeeting

Oscilloscope? You mean a multimeter right? Or do I have to break off some electicall mumbo jumbo. Seriously to check for a voltage drop you can do a coninuity to ground or impeadance test (ohm load) from the engine to the negative battery post and the actual frame. This should give you a real good idea of whats goin on. Q's give me a pm

AAmeeting

I forgot to mention. What you are expieriencing really sound like some sort of sensor.