I have a 2000 F350 4x4 CC with the 7.3.
Sometimes when it is idling my idle will go up to about 900 then drop to about 5 or 600 then back up to normal idle about 750rpm I have no idea why it does this. I have changed the air filter, oil, fuel filter, and checked for water in the fuel still it does this from time to time. It does it if I am in stock mode or any HP mode. Any suggestions would be appreciated.
Thanks Al

 

i might check the ipr nut.
how many miles on the truck?

 

IPR nut, IPR sticking, ICP sensor... these are common issues popping up right about now on this age of truck.

 

I have 262,000 miles I had just replaced the ICP but it was doing this before
and Thank you for the replies.
Al

 

If the ICP is new....ish then it sounds like your IPR is STICKING SHUT and HPO pressure is building just briefly enough to send more fuel than desired. Either raising HPO pressure or increasing Pulse width on the injectors briefly will cause it to raise RPM. Are you having any transmission issues? If you have an automatic and the flexplate is cracked.........that is a large stretch so I am going with IPR.
Dwayne

 

Can you tell me more about this? I never heard of this and I don't understand how the flexplate comes into play. Lope? Slow rise and fall on the idle?

 

No trans problems.
It is really strange does not do it all the time but that is actually what happens does not always go as high but will jump a 100 rpm then down then back all happens with in a couple of seconds.

 

If the flexplate cracks and lets the transmission loose then the engine will really overspeed. It would be similar to running an engine without a transmission attached. NO LOAD whatsoever. It would be a ten million in one chance that it could happen. Mostly I wanted him to focus on an IPR that has 262K on the clock.

I would have said to look for leaky up pipes but that would lead to less boost and the RPM going low....not high. But he probably does have leaky up pipes....it is just not contributing to the high blip on the idle. Merry Christmas and Happy the World Did not end day LOL.

 

Thank you for that, I learned something new.

As for the idle, how many miles on your oil and what type is it? The IPR is new-ish, but a lying Injector Control Pressure sensor can do weird things. Inspect your ICP Sensor, it is in the picture below, just above the "T" on the T-500, near the very top of the photo. Inspect it for leaking oil or a bad/dirty connector. Check the nut on the IPR (straight left of the "T" of the T-500)... that nut is so flimsy it can work its way loose.

 

The icp sensor is new I will check ipr.
Thanks

 

Thanks to all that replied you were right I found the problem.
THE IPR NUT HAD FALLEN OFF SO THE PARTS WERE MOVING.
Put it back on and it is perfect.
I think I am going to replace the IPR just to be safe.
Once again Thanks
Al

 

Congrats! The best-priced fix: Free. IPRs aren't cheap, so that gets replaced only as needed.

 

even then...
a quick teardown and cleaning of the ipr generally clears up sticking issues... easy peasy to do and again... no buckzooka ammo required.


and now is as good a time as any to remind about the passenger side fuel line. its not a bad task if you pull the cac tube from the spider on that side for wiggle room.
its not pretty when that line finally wears through... easier to prevent it than deal with the aftermath of 55-70psi diesel fuel spewing all over your engine compartment.

 

Thank you for the info



UOTE=Christof13T;12643063]even then...
a quick teardown and cleaning of the ipr generally clears up sticking issues... easy peasy to do and again... no buckzooka ammo required.


and now is as good a time as any to remind about the passenger side fuel line. its not a bad task if you pull the cac tube from the spider on that side for wiggle room.
its not pretty when that line finally wears through... easier to prevent it than deal with the aftermath of 55-70psi diesel fuel spewing all over your engine compartment.[/QUOTE]

 

I am not familiar with the passenger side fuel issue can you explain. Thanks