OK, let me try this again...

why does my truck idle so high in neutral after Ive been driving?
idles at 1500 and then 2000, has happened stop and go towing
or freeway miles not towing.

 

I did a search and I couldn't find this problem, but I'm sure its happened before...

98 12v 5speed manual
After driving just a few miles, the rpms don't drop down between shifting,
they stay up, to 1500, then 2000 rpms, it stays high as I shift between gears.
When I stop and put it in neutral, the engine is just revving at 2000,
when I shift into gear it takes off.
No problems with shifting , the gears shift smoothly.
Happens whether I'm towing in stop and go traffic,
or I'm cruising freeway miles.

After I got home I noticed the engine seemed warmer than usual (normal temp on the dash gauge)
and the overflow tank was empty, but there was coolant in the radiator and the engine wasn't super hot at all.

when i did my kdp/ps/vac booster,
I readjusted the speed sensor, removed and reinstalled my intercooler boots, removed and reinstalled my radiator, replaced my radiator hoses,
cleaned my solenoid and replaced the boot, reinstalled the fuel prefilter with a new screen, fiddled with the fuel hoses a bit, removed the fuel filter but reinstalled the same one, since it was new 2000 miles ago......and oh yeah I had to replace the starter.

I did find that my speed sensor wasn't secured, and the wire loom had been rubbing on the serpentine belt. the green wire had a little insulation rubbed off but the wire seemed intact, I just taped it and secured the loom out of the way.

I figure I gummed up something, ..where do I look?
thanks

 

Try lowering your idle a bit. My dually started doing that, although it would only go to about 1500 rpm. I just lowered the idle once it was up to temp, and it has been well. Its starting to creep up again, but its only at 1k rpm. I never did find anything on here that would point out where to look. I'd suspect something in the governor, but what? I don't know.

 

Any missing or broken return springs?

Check your throttle cable i may be binding also check the throttle linkage for free movement it might need a little lube.

 

+1... I had this issue... I cleaned and lubed the linkage.. installed a new return spring and never had a problem again.

 

Thanks, I'll give the throttle cable and return springs a try...
if its still a problem I'll check the idle when its warm.
Didn't used to happen though...

 

Mine started doing it 5 months after I did the conversion, all the linkages were good, the throttle lever was against the idle stop screw. I never did figure out why it did that.

 

which conversion?

 

I p-pumped my 24v.

 

sticking rack?

 

Should ask, will it do it when its cold? When my truck was acting up, it would fire up cold at the normal rpm. Even just letting it idle for 3 or 5 minutes, the rpms would creep up to about 1400, with no driving at all. It would fire up at about 850 rpm cold. When I adjusted the idle, it would fire up at 750 cold, and idle around 900 hot.

 

reducing the idle speed dosnt fix the problem. its like giving a cough drop to some one with strep, it keeps your throat from hurting....so no more strep??? start with cleaning the links and cable then check your tps. if thats not it CALL a certified Dodge or Cummins tech.

 

OK, I want to lube the throttle cable

Looked in my Haynes and it wasn't clear to me how to do it,
plus they gave a bunch or warnings that you could mess things up

So can anybody tell me how to do it, and exactly where to look?
I was hoping to do it this afternoon before I tow 200 miles tomorrow

I have no idea about this stuff...
thanks

 

Mine did this last year, come to a stop light and rpm's would stay high. Try manually moving the throttle by the TPS(engine not running) all the way a couple times and see if it returns all the way to it's stop. If not lube w/WD the whole linkage to figure out where it's binding. On mine it was the big spring at the TPS. Hope this helped

 

I found the throttle linkage cable (?)in the engine bay, shot it with WD40.
also (unwisely I'm sure) I blindly sprayed a shot of WD40 up in the area where the cable enters inside the cab.

Worked great, high idle problems gone. As always, thanks for the help!