Jeep Liberty CRD - Uncommanded Accleration

[Silber Igel]

Gents,

My neighbor has an '06 Liberty CRD with about 35K miles on it. Its a great car but now has a problem. About two months ago it lost power and died. The dealer replaced a 'turbo tube' and the EGR valve under warranty. The CRD ran fine for about a week when it suddenly accelerated. Its been at the dealer for about a month. The problem happened again right after it was brought back to the dealer and despite being driven daily for a month it hasn't re-occurred. It set one code: "brake and accelerator on at the same time" and then nothing.

Now he's afraid to sell it and afraid to drive it. He has filed a notice with NTSB. There's absolutely nothing on the web about this problem....

Anyone else have a similar problem with a CRD or any other diesel engine? If so, what was the cause?

TIA!

 

[benjamming]

What was the actual code #?

 

[dnowak]

check on lostkj.com and jeepkj.com two sties for the liberty.

 

[GMBoy]

Sounds like the problem was that he was stepping on the brake and the gas at the same time. Whenever I've read stories about "unintended acceleration" the root cause was determined to be driver error. I never believed it myself until one day I did it to myself wearing fat boots! My foot was on the gas more than the the brake so even though I thought I was pressing hard on the brake, the gas was getting more pressure.

 

[Shannow]

If it's a fly by wire this can happen.

Mate had an Audi, and it started revving/accelerating, backing off when he was at speed and all sorts of tricks.

 

[V1]

There were some Mazda6 owners who experienced some idle surging, and situations where the engine did things it wasn't told to do. It turned out to be a string of faulty electronic throttle bodies.

This could very well be part of your neighbor's problem, Silber. Does his Jeep have a fly-by-wire throttle system?

 

[PT1]

If it is drive by wire it may be a bad electronic throttle control or throttle position sensor. My GMC ETC has disconnected once and sent me a "powertrain suspended" message. The dealer has not been able to reproduce the event and it left no code or history in the ECM. I do think it's probably a bad ETC. I don't know if his dealer can re-flash the ETC or not but I would start there.

 

[Gary Allan]

I can't wait until "steer by wire" is common. That should make things real interesting.

 

[mrsilv04]

A bad throttle position sensor can scare the living daylights out of you. I had a Mercury Cougar that went through several TP sensors in a few years. I'd get a few seconds warning (the engine would shudder), then the throttle would stick at 3,000 RPM.

Every time one went bad, the dealer would replace it for free. Several different mechanics worked on the car, and even a few regional Ford specialists, and no one could ever get to the root cause of the problem. I chalked it up to it simply being a Ford.

 

[eljefino]

On the gas throttle-by-wire cars they almost always have a mode where if you touch the brake pedal it returns to idle as a failsafe.

Where this is a diesel, there is no physical throttle, so I bet if one looked at the acellerator pedal it would pivot on a potentiometer and no cables would penetrate the firewall.

If it were gas I'd worry about the throttle blade getting sticky over time or the servo motor wearing out. But since it's diesel I would place my bet on bad computer glitches commanding more fuel than required.

Apparantly back in the day you could have a diesel get hot enough it would start burning its own motor oil and run away until it blew. I have to imagine a couple safeguards have been invented to coincide with the computer controls since then.

 

[brianl703]

Originally Posted By: eljefino
On the gas throttle-by-wire cars they almost always have a mode where if you touch the brake pedal it returns to idle as a failsafe.


Man...what are the two-footed drivers going to do?

 

[Aldaris]

Originally Posted By: Shannow
If it's a fly by wire this can happen.

Mate had an Audi, and it started revving/accelerating, backing off when he was at speed and all sorts of tricks.

Accelerates
Under
Demonic
Influence

 

[scotthershall]

If they were fiddling with the turbo they could have gotten some oil into the air intake. It's then possible for that oil to get sucking into the engine... being a diesel it would have burned the oil just like it burns diesel fuel. Also, since it's diesel, there is no trottle plate to restrict airflow. The end result is a engine runaway/power surge.

This is one of the problems with a turbo-diesel. If the turbo's seal fails, which likely will dump lots of oil into the intake causing the engine to runaway. VWs have an intake valve (anti-shutter valve) that closes when the engine is turned off. It serves to make shut down smoother (prevents "dieseling" like in an old gas engine), but it also stops a runaway so long as the driver turns the ignition off.

This is one possibility. I'm not sure if the engine has a code for a runaway. Maybe it defaulted to a throttle input code since it couldn't control the engine's speed.

Also, throttle-by-wire systems should have a failsafe, too. Again, speaking of Volkswagen... there should be two sensors in the pedal, and if they don't agree (because one failed) it will cut the throttle. The ECU will possibly hold the engine at 1200 or 1500 RPM to allow you to move the car or limp it home.

Scott