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2006 Subaru Tribeca car bucking and accelerator stopped!

I own a 2006 Subaru Tribeca with 125,000 miles. It has been well maintained and a great vehicle. On a recent long distance trip, after driving about 7 hours, going 70mph, the car started to buck and the accelerator stopped responding. It continued to lose speed as I pulled off the side of the highway. I turned the car off and restarted it and attempted to drive it but it wouldn’t go over 10-15 mph. I didn’t have any check engine lights. Called AAA and had the car towed 4 hours to our final destination. The mechanic has had the car for 4 days and can not find the cause of the event. I have a 22 hour drive back home in a month and I am extremely concerned. Did some research and have found others have had the problem but had codes come up. Research says it could be throttle pedal position sensor/ pedal assembly. I sure would appreciate any help. Thank you!

My prime suspect would be the throttle position sensor, even if there are no codes.

However, my fear at this point has to do with the damage that was done to your AWD system and (possibly) the transmission if the vehicle was actually towed. I’m really hoping that you had it put on a flatbed auto transporter, as Subaru requires.

Towing is a BIG no-no with AWD vehicles, and it results in big repair bills.

Oh yes it was on a flat bed.

Thank you VCdDriver. When I spoke with the mechanic he wanted to do more research and didnt want to just throw parts at it. I appreciated his caution, all research I saw pointed to the TPS.any other suggestions?

Your mechanic’s caution and his reluctance to just “throw parts” at the problem are to be commended. Hopefully he will figure out the exact nature of the problem sooner, rather than later.

The throttle on your vehicle is electronically controlled.

This means that there’s a throttle PEDAL position sensor that informs the computer at what position the throttle PEDAL is at.

The computer then takes this information and applies it to the electronic throttle body.

More than likely the problem is with the throttle PEDAL position sensor.


The tps should be fairly simple to test, doesn’t take much time to determine if it is working or not. That shouldn’t take 4 days. I presume your shop has done that already and thinks the tps isn’t the problem. It’s very unusual this wouldn’t produce any diagnostic codes. I presume your shop has checked for active and pending codes in the computer memory right? And that the battery didn’t get discharged or disconnected between when this happened and when they read the codes – otherwise the codes that were stored would get erased. When you turn the key to “on” but don’t start the engine, all the dashboard lights that are supposed to come on, do right? Otherwise you may have a burned out warning light on the dash.

For this kind of symptom you’d have to have something wrong in a major way with one or more of these functions

  • fuel metering
  • air metering
  • compression
  • spark
  • ignition timing
  • valve timing

Unless they happen upon a lucky guess, the shop will just have to go through those one by one. Start with a fuel pressure measurement for example.

There’s a couple of other things you could try. First, I seem to recall a problem with similar symptoms reported here that turned out to be caused by a problematic variable valve timing actuator. You might search this forum for that thread. Second, you may need to get a dealership shop involved, at least to the level where they search the technical service bulletins and recalls for this car to see if anything might apply.

BTW, with a symptom so noticeable, there’s a reasonable chance the problem won’t be overly expensive to correct, once it is properly diagnosed. Best of luck.

Thank you Tester, that is helpful. All o know is how to take the car to a good mechanic.

Thank you GeorgeSanJose. Wow, that was a lot of good information as well. The mechanic wasn’t able to get to the car right away, but was able to check the codes stored in the vehicle. None of them related to the problem. I don’t have access to the car, but will make certain none of the lights are burned out. I will go thru the archives to look for the post about the variable timing actuator. I don’t have the greatest trust in the dealership close by, since they took 3 hours to replace a headlight and then put it in crooked. The next closest is an hour away, but my be my best choice. Im from up north and Subaru’s are very common, but down here in Florida, folks don’t need 4 wheel drive.
I appreciate all the great formation your provided. Thank you

Yes, that’s definitely a problem with owning a Subaru in warmer climes. Just not many of them on the road, so not many shops there tooled up and schooled to service them, especially for difficult to diagnose problems.

GeorgeSanJose would there be information that only Subaru repair shops would have access to?

Yes, there could be. Most inde shops who subscribe to service-data databases like All Data would have access to most of that manufacturer technical service and customer interest bulletin information too. If you can’t find someone to look through it, ask your local public library. They may subscribe to All Data or something similar.

Mechanic has car now? 6+ hrs of labor and no issues but it still cannot drive over 15 mph?