2005 CRD - Runaway throttle

bugnout · **Posted:** Wed May 26, 2021 2:30 pm

I picked up my boat from storage and towed it to the landing. Its about 20 miles and I towed in 3rd gear. About half way to the landing I noticed that my Jeep did not slow down when I took my foot off the accelerator. When I got to the turn to the landing, I really had to stomp on the brakes to slow down. I got it off the main road and realized the engine wasn't slowing down. I put it in neutral and the RPM's went immediately to red line. I shut off the motor. I tried stopping and restarting and each time it goes to max throttle.

Nothing on the pedal, it moves freely.
Nothing apparent and not throwing any codes.

I got my wife to bring the truck over and I finished launching the boat with it.
I disconnected the battery and left it, haven't gone back yet to see if it resets.

Anyone ever had this happen? Its like the pedal position sensor may have gone. What else could cause this?

bugnout · **Posted:** Wed May 26, 2021 4:29 pm

Well, when I reconnected the battery, the issue had resolved itself. I guess it was just a computer glitch, lost communication with the accelerator pedal module. Weird.

Just for background, the Jeep has been sitting in my garage since November with the battery disconnected. I got it out two weeks ago and have driven it 3 or 4 times for short trips before using it to pickup the boat today.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Runaway diesel is definitely a thing, but I'm not sure how it happens in a common rail setup. I'm dubious of the throttle pedal explanation - there are numerous safeguards in place to prevent such a thing from happening. I would be more suspicious of something like a dying turbo sending oil into the engine... It'll burn a lot like diesel.

bugnout · **Posted:** Wed May 26, 2021 11:03 pm

thesameguy wrote:

Runaway diesel is definitely a thing, but I'm not sure how it happens in a common rail setup. I'm dubious of the throttle pedal explanation - there are numerous safeguards in place to prevent such a thing from happening. I would be more suspicious of something like a dying turbo sending oil into the engine... It'll burn a lot like diesel.

Could be, but from what I've read, if my turbo was dumping oil into the engine, shutting down using the key wont work. The engine will keep running until the oil runs out.

layback40 · **Posted:** Thu May 27, 2021 6:47 pm

Common rail has no effect on a true run away.
Oil seal on turbo fails and feeds oil into engine.
If its up to temperature, it will rev up until it goes bang. Happened a bit with om6xx mercs.
Best way to stop is to block air intake.
Maybe the butterfly in the intake closed and shut yours down?
If you have a manual, you can put in top gear and brake till it stalls. Doesnt work with an auto.
On a 2 stroke Detroit, they have a knob on the dash to shut a butterfly and so stop the engine.
I had it happen to me in a pickup with a Izuzu turbo diesel, doing about 45mph, it just took off with a ton of white smoke out the back. Turned engine off and braked hard, it came back under control when it was nearly stalling. Scared the XXXX out of me!
Dont think from your description that it was your problem.

bugnout · **Posted:** Mon Jun 07, 2021 11:31 pm

Well, it happened again. This time I just let it cool off and it corrected itself. Anyone have any idea where to look first?

No codes thrown
Seems to be heat related. towing both times it occurred.
Throttle still responds when I depress the go pedal - So I can accelerate, but it doesn't slow down when I take my foot off the pedal. Braking and down shifting will slow the vehicle, but putting it in park or neutral the engine goes to max RPM.

Its like the fuel rail pressure sensor is stuck or reading incorrectly
or
the fuel pressure regulator is misbehaving.

What are your thoughts?

PZKW108 · **Joined:** Sun Apr 06, 2014 5:23 pm **Posts:** 461

bugnout wrote:

Well, it happened again. This time I just let it cool off and it corrected itself. Anyone have any idea where to look first?

No codes thrown
Seems to be heat related. towing both times it occurred.
Throttle still responds when I depress the go pedal - So I can accelerate, but it doesn't slow down when I take my foot off the pedal. Braking and down shifting will slow the vehicle, but putting it in park or neutral the engine goes to max RPM.

Its like the fuel rail pressure sensor is stuck or reading incorrectly
or
the fuel pressure regulator is misbehaving.

What are your thoughts?

Fuel rail pressure should have set a DTC like P0087 or P0088 !

rankom · **Posted:** Tue Jun 08, 2021 10:48 pm

try flushing out air to air intercooler make sure its free of oil. that would fix your issue.

bugnout · **Posted:** Wed Jun 09, 2021 12:02 am

rankom wrote:

try flushing out air to air intercooler make sure its free of oil. that would fix your issue.

I'm not sure I follow. Are you suggesting that the intercooler might be full of oil from the crankcase breather?

WWDiesel · **Posted:** Wed Jun 09, 2021 2:22 am

bugnout wrote:

rankom wrote:

try flushing out air to air intercooler make sure its free of oil. that would fix your issue.

I'm not sure I follow. Are you suggesting that the intercooler might be full of oil from the crankcase breather?

It can happen, especially if you don't have a ProVent filter installed.
Back in 2013 when I first got my Jeep CRD, I pulled the intercooler and found it had well over a pint of oil in it from the puck breather.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Mine had a fair amount of oil in it too... When the engine was out, at one point I set the intercooler upside down in the garage and came back a few days later to a puddle of oil. It was not a pint, but it wasn't nothing. More than I got out of my XR4Ti's intercooler when the turbo had totally failed.

I would think if the *actual* throttle continues to work properly but idle control is gone, oil is the likely culprit. Maybe not enough to run the engine such that turning they off shuts it down, but enough to juice to the engine. At the very least I'd be puling the CAC hoses, and poking around. I really have a hard time accepting the fuel injection is the problem... there are so many safeguards in place if the pedal/pump/sensors were having an issue, there would be a CEL. Do you have a scan tool you can use for a sanity check? Make sure those sensors are reporting sane values?

bugnout · **Posted:** Wed Jun 09, 2021 7:39 pm

Yeah, ok, I'll be checking the hoses and the intercooler this weekend. Maybe the turbo is throwing oil after its warmed up. I've had the breather going into an elephant hose for years so no oil into the intercooler from there.

bugnout · **Posted:** Thu Aug 12, 2021 7:17 pm

Well I'm suspecting the turbo seals. The engine oil was almost completely depleted. The turbo hoses have a fine coating of oil, but not dripping. The turbo oil supply line is wet. I haven't taken the intercooler out to inspect yet.

So is there anything else I can check that might cause this or am I replacing the turbo? I have 180k miles on the original so I guess that is not bad.

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

The supply line is wet *externally*?

Possible valve stem seals are leaking?

bugnout · **Posted:** Fri Aug 13, 2021 7:47 pm

thesameguy wrote:

The supply line is wet *externally*?

Possible valve stem seals are leaking?

The supply line is covered with oil.

By Valve stem seals do you mean Oil feed line seals?

Could leaky feed line seals cause oil to be pulled into the turbo inlet side/

thesameguy · **Joined:** Sat Oct 01, 2016 8:24 pm **Posts:** 652

Do you know where the supply is leaking? While not impossible I think it would be unlikely an external oil leak and would be at fault here, but it does raise some other questions.

The valve stem seals are located at the top of the intake and exhaust valves. They prevent oil in the head from entering the combustion chamber. If your valve steam seals are seriously leaky, it's just a constant supply of oil in the cylinders. I think this is reaching - but if the turbo isn't leaking then something somewhere else is.

bugnout · **Posted:** Sun Aug 15, 2021 6:28 pm

The head has about 40k on it since it was rebuilt. I guess it could be seals

There is another element here though, "Time". The runaway doesn't happen until I've warmed it up and driven it at highway speeds for about an hour.

Turbo seals sound more likely since it is original at 180k miles. The fine oil in the charge hoses could only have come from the turbo and if the turbo because I haven't had the crank case vent connected for a number of years. If the turbo is hot and the oil is at temp then I'm guessing that the oil will atomize pretty well to put that fine coat on the hoses. I'll have to take the intercooler out and see how much oil is in it.

I'm not sure how I can test out this theory. just want to make sure the turbo is the most likely cause before I order one.

layback40 · **Posted:** Sun Aug 15, 2021 9:09 pm

For starter, take the inlet air hose off the turbo and see if there is any movement in the air wheel. 5 minute job! Any radial movement at all and you know you need a turbo. You may also feel some oil on the fins of rhe wheel.

bugnout · **Posted:** Tue Oct 12, 2021 12:22 pm

So appears that replacing the turbo solved this issue. It was rather strange that the runaway throttle only occurred after about an hour and a half of operation at temperature. Replacement came from Sasquatch. Replaced the manifold gasket, copper crush washers on the supply line and the rubber gasket on the return line.

2005 CRD - Runaway throttle

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