Choke?

[Jcode]

Does the 6.2 have a choke? When I started my truck this morning, as soon as I touched the accelerator, the RPMs revved WAY up and stayed there until I put it in gear (hated to put it in gear with the engine taching so high), at which time it the RPMs returned to normal(felt like an automatic choke on a gasser disengage).

The RPMs were crazy high. Glad it wasn't any colder outside than it was (mid 40's). I always try to take it real easy while the engine is cold and let temps get to normal range before even driving normally, so needless to say I almost cringed when I heard the cold engine rev like that. How can I disconnect whatever caused it to do this?? Appreciate the help!

[DmaxMaverick]

No choke. Unless the air filter is plugged. A choke on a Diesel is counter-productive.

Check for a sticky throttle cable or linkage. Otherwise, read on....

You probably had a slug of air in the fuel line. If you have any leak in the system, colder temps will bring them out. After a hot shutdown, the temp change from hot to cold will contract the fuel and air in the system, including the tank. This creates vacuum, and will exploit any opportunity for air to get in. Lower tank levels are worse (more air to contract). If you are looking for something to fix, replace the fuel cap. A sticky vent will allow this to happen when it shouldn't.

[Subzilla]

When you touched the accelarator, usually the HPCA (housing pressure cold advance) / Fast Idle solenoid kicks in. This aids in cold start up and will normally kick the rpm's up some 500 or so until a sensor in the block says it is warmed up enough. As Dmax said, maybe a sticky throttle cable or some other wierd situation caused it to jump up even more. Then maybe, I'm guessing, it was a coincedence in timing that when you put it in gear, the sensor gave the "warmed up" signal to the solenoid and kicked the fast idle off.

Does it do the same when it's whened up?
Has it done it before when cold? Maybe it was colder this morning..
See if it does it tomorrow morning or next time when it's cold. The fast idle can be set as soon as the ignition key is turned on and the glow plugs are firing.

I actually have a switch to bypass the fast idle just so it won't run high for any longer than I want it to, which is usally after 10 seconds or so.

[Jcode]

Thanks for the replies! Yes, it normally does do this when it is cold, but has never revved this high.

I had just changed the fuel filter the day before (although when I shut it down it was running fine) so there may have been some air still in the system.

How can I disable the fast idle (where is it located)? Thanks.

[DmaxMaverick]

The high idle solenoid should above the IP, toward the front. It's about the size of a 35mm film canister, and has one wire attached. It is adjustable (the hex/slot turns). Disable it by unplugging the connector.

If you recently changed the fuel filter, it could still have some air in the system. It depends on how long or how hard you ran it after the change. Air in the system does a couple things. It acts like an accumulator in the IP and injector lines (stores pressure), which retards the timing and delays/lengthens the injection event. This creates a condition of high no-load revving and delayed throttle response. Many times, accompanied with more white smoke than normal.

If you have run it enough to bleed all the air, you likely have an issue with prime-loss during cool down (overnight). This can be caused by a few things. First, if your fuel filler cap is old or original, replace it (cheap). Be sure to get a new Diesel fuel cap. A stuck vent can cause excessive vacuum in the tank and fuel system as it cools overnight. This will exploit any possible air intrusion. If you have a gasser cap, it won't vent properly, either. If they injectors are worn out, they can/do allow air to be sucked into the system during the cool down, or gravity (siphon, via the return lines) if they're really sloppy. This condition will usually be more exaggerated with less fuel in the tank (more air space). If the fuel system has any evidence of fuel leakage/seepage, suspect it as a possible air intrusion point.

[Jcode]

It was the high idle solenoid. The next time I cranked it, I did not touch the accelerator and it seemed to start and run fine (normal rpm's). After it idled normally for 1-2 minutes the rpm's all of a sudden jumped WAY up like it had been doing before(without me touching accelerator). I popped the hood and unplugged the high idle solenoid and the rpm's went back to normal. Appreciate the help.