94 Subaru Legacy 89k miles.

 

While driving home on the highway tonight, it started bucking intermittently. I wasn’t accelerating or decelerating when it started, just cruising at about 60mph. I downshifted to slow down and see if it did anything to help. It did for a second, then started up again. Luckily, I was at my exit. As I was going off the ramp I threw it into neutral to see if that would help matters and the bucking stopped.

 

At the bottom of the ramp, at the stop light, I revved the engine a little, and there was no stutter or bucking there. I put it into 1st gear, it went forward OK for a little bit but started bucking again slightly AND the “Check Engine” light came on. I was only ¼ of a mile from home, so I took it easy. Right before I pulled into the driveway the Check Engine light went out, and the bucking stopped.

 

Is this something as simple as a tune-up needed? Maybe there's something that needs to be flushed out? Any suggestions?

You need to read the codes to start with. If it has not had a tune up and fuel filter change that would be due.

Check out my site. It has the procedure on how to read the codes and what they are

 

www.surrealmirage.com/subaru/engine.html

Intermittent bucking, especially after a highway run is often the spark plug cables failing.

Coil pack is also a point to consider, but I'd start with new genuine Subaru plug cables.

 

Of course, that does depend on the ECU codes.

It was the air flow meter assembly. The shop said the diagnosis code indicated that the computer controlling it was shot. I also replaced the air filter since it was pretty filthy.

 

Question, how much is a reasonable amount for a repair shop to charge for the diagnostic test? I felt like I was in a bind so I just paid for it, but it seems like something that should be real cheap. Isn’t it just hooking the car up to a computer and looking at the results?

 

Anyway, thank you for your help. This board never fails to impress.

Well autozone does it for free. Any shop that touches the car will be charging a 1 hour minimum fee unless posted otherwise.

 

nipper