Fluctuating Idle

[Dan R]

Hello, I just bought a 99 250 7.3 PSD. It's great and I would never buy another gas powered truck. The only problem (?) I have is a weird idle when it is cool, the RPM's jump and drop for the first 30-40 seconds, but it is fine once it gets warmed up. This is my first diesel vehicle, but I don't think they are supposed to do this. Anyone else have this problem or know how to solve it? Thanks, Dan

[Medic 66]

What is the outside temp? This may be normal.....

[MTDewX]

on chilly mornings, my (exhaust) sounds like a mini me jet engine due to some thing that closes to help the engine warm up faster. its normal from what I have read. I don't know the name cause I am new also, but boy do I read on this site. and learning everyday

[Dan R]

I should have explained it better, its not just holding steady at 2k or so RPM, it jumps 1000-2000-1000-2000 (very quickly, every second or so, sounds like someone is pumping the "gas" pedal). I know most vehicles initially run at a higher RPM when its cooler to help warm up, but this fluctuates, and sometimes it will stall.

[amiller93]

Whats the Oil Level, Oil Type, Last Oil Change

High pressure oil drives the injectors low, old, thin oil can cause the "romp-romp" idle

[DP-Tuner]

Originally Posted by Dan R

Hello,

I just bought a 99 250 7.3 PSD. It's great and I would never buy another gas powered truck. The only problem (?) I have is a weird idle when it is cool, the RPM's jump and drop for the first 30-40 seconds, but it is fine once it gets warmed up. This is my first diesel vehicle, but I don't think they are supposed to do this. Anyone else have this problem or know how to solve it?


Thanks,

Dan

If you can borrow a scan tool to see what is going on at that rpm. It almost sounds like an ICP issue. It is like it is trying to compensate the ICP(injection control pressure). Could be that it has a programmer on it and was not returned to stock or a chip possibly. Look on the J3 port on the PCM. Behind the emergency break there is a black plastic housing encasing the PCM. Let us know what you find.

Diane

[EWALR1]

i am also having the same problem with the eratic idle. i have changed the high pressure pump, ipr,icp,idm,pcm,wiring harness,valve cover gasket, injector harness,cps, and all 8 injectors. still no luck with the idle. changed the oil several times and still no differance. its not too big of a problem but id still like to know what it is. the only difference is min only does it for about 10-15 seconds. im pulling my hair out trying to figure it out. if anyone has some ideas it might help both of us out, but im gonna keep trying to solve it.

[lesarjohn]

Mine too. At startup, after not running overnight, and not everytime. Touch the gas pedal a bit and it goes away and idels right?
It used to on anything less that 40 degree(f) mornings it would idle pretty high for a few minutes. Not anymore.

Does this give anyone any better tips. Going on a long haul next week and would like to sleep better?

My scan tool was ordered last week and has not arrived yet?
Does anyone have one locally that I could check it out with
Guelph, Ont, Canada

[Dan R]

It sounds like we have the same problem, yes when I touch the pedal it does go away. No one has fixed this before?

[Tenn01PSD350]

Gonna bump this for you guys because I don't feel like you're getting what you need. Initial search looks like it may be the accelerator pedal specifically the idle validation switch which is in the pedal assemby. Especially since it goes away if you press the pedal. It's all fly by wire gents. An entire assembly. Yeah, gotta love it.
*Condition , * Possible Source, *Action

Irregular Engine Idle Speed (Diesel)

Incorrect engine idle speed adjustment or idle validation switch.

REPLACE the accelerator pedal and sensor assembly.

[lesarjohn]

Thanks I will investigate that more!

[Kwikkordead]

Originally Posted by Tenn01PSD350

Gonna bump this for you guys because I don't feel like you're getting what you need. Initial search looks like it may be the accelerator pedal specifically the idle validation switch which is in the pedal assemby. Especially since it goes away if you press the pedal. It's all fly by wire gents. An entire assembly. Yeah, gotta love it.
*Condition , * Possible Source, *Action

You're the first one that I have heard from that actually has an answer for the morning romp romp idle.
I'll bet that Ford sells a lot of pedal assemblies this week!

.

Another thing that might help is to install a high pressure crossover line. That smooths and quiets the idle.
However, don't install the HX line to try and cure the romps, but rather install it after you get the problem solved.

[Tenn01PSD350]

Originally Posted by EWALR1

the only difference is min only does it for about 10-15 seconds. im pulling my hair out trying to figure it out. if anyone has some ideas it might help both of us out, but im gonna keep trying to solve it.

I would not worry about this if it only does it for 10-15 seconds. I would only really look at the pedal assembly if an idle problem persists after 1-2 minutes. On cold starts, there are a lot of parameters that need to get up to speed, so time must be allowed for that before blaming the pedal assembly. I would suspect the pedal if it idles poorly even after warm. Don't want a bunch of pedal assemblies being bought when not needed.

[amiller93]

The IVS is a Prime Suspect for the Romp Romp but there are several other Idle Quality possibilities.

Poor idling
Vacuum leaks.
Refer to the appropriate section in Group 303 for the procedure. REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.

Malfunctioning or damaged ignition system.
Refer to the appropriate section in Group 303 for the procedure. REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.

Malfunctioning or damaged fuel system.
Refer to the appropriate section in Group 303 for the procedure. REFER to the Powertrain Control/Emissions Diagnosis (PC/ED) manual.

Damaged valve tappet or lash adjuster.
INSTALL a new valve tappet or lash adjuster.

Damaged valve tappet guide or lash adjuster.
INSTALL a new valve tappet guide or valve tappet.

Incorrect valve-to-valve seat contact.
REPAIR or INSTALL a new valve or valve seat.

Damaged head gasket.
INSTALL a new head gasket.

AND This

10b. Low Idle Stability (ICP Pressure)
Purpose:
To determine if idle stability or low power is caused by a stuck or dirty IPR or faulty ICP signal.

Recommended Procedure:
Install NGS Tester. Turn A/C off. Access ICP PID on NGS Tester and monitor ICP pressure. Operate the engine at low idle. If engine does not stabilize, disconnect the ICP sensor. If low idle speed stabilizes with the ICP sensor disconnected, the problem is most likely in the ICP sensor circuit. GO to Pinpoint Test DC . If rpm does not stabilize, change the IPR and retest. This test should be performed with engine at normal operating temperature.

Possible Causes:
Debris stuck in the IPR
Inoperative ICP sensor or circuit failure

AND This

10a. Injection Control Pressure Tests (Oil Aeration — Poor Idle Quality)
Purpose:
To determine if the engine lube oil is aerated and causing poor idle quality.

Recommended Procedure:
Install NGS Tester. Turn A/C off. Access ICP PID on NGS Tester and monitor ICP pressure. Operate the engine at 3400 rpm for 3 minutes. This test should be performed with engine at normal operating temperature.

Possible Causes:
Extended oil drain intervals — the anti-foam additives in the oil may be depleted either from severe use or extended intervals.
Air may be present due to recent engine repair on injection control pressure system. It may be necessary to run the vehicle aggressively for 24-32 kilometers (15-20 miles) to remove air.
Wrong type or grade of oil.

[Tenn01PSD350]

Thank you Alan. I did not want to go digging for those because everytime I get into that DVD, I find more and more interesting things and get stuck there.

Also, I would hate for somebody to misdiagnose the pedal and not cure the problem.