My 2003 Baja is having some bizarre purge issues when the temps outside go above 90 degrees. The Subaru mechanics at my dealership have identified the problem, but haven't been able to fix it, so I'd like to get some ideas as to what my next steps should be
About a year ago, my Baja started "bucking" in hot weather. This happened most frequently when I would get off the freeway after about 15-20 minutes of driving, or for a mile or two after filling the gas tank. I got the mechanic to take a drive with his laptop diagnostics hooked up, and he found that the A/F sensor was swinging between a rich and lean mix when the bucking was occurring, so I had them replace it. Things seemed to improve after that, but the weather had cooled down, and car was still bucking after filling the gas tank.
This summer, it started doing it again, so I went for another drive with the mechanic, and this time he noticed that the purge solenoid was opening up all the way when the car was bucking. The A/F sensor was acting up again too. He thought the purge behavior was not normal, so he bypassed the solenoid by plugging the manifold inlets and unscrewing the gas cap, and had me drive it over the weekend. It drove beautifully...no chugging at all...but I noticed is that I never got a warning due to the loose gas cap, which seemed odd.
I brought it back to the shop on Monday, but when I picked it up again in the afternoon, the mechanic told me he had changed the A/F sensor again, but had done nothing to the purge system. I was not too happy about this, but he said he'd test driven the car with the solenoid bypassed and could still see the A/F sensor hunting between rich and lean. He also said he talked to Subaru tech support, and they were unable to tell him what inputs controlled the purge solenoid. I found that a bit hard to believe, as I could find that information easily enough off the web. When I questioned the shop manager, he said that they had some other ideas, but they were "expensive", so they decided to replace the sensor again because it was still under warranty.
Anyway, things again seemed better after the sensor replacement, and the bucking seemed to be much reduced after filling the tank. However, the weather had cooled down, so I really couldn't tell if it was a true fix. Now that the weather has gotten warmer, I definitely notice the car bucking again when coming off the freeway, so I will have to take it in for further work.
If anyone has an idea of what's going on here, I'd greatly appreciate some suggestions. I love my Baja, but I've had so many expensive engine problems in this vehicle over the past 5 years, I'm at the point where I'm about ready to cut my losses and sell it if I can't get this fixed.
Based on my research, I think the following components could be involved, but I don't know how to rate them in order of how likely they are to be causing it:
Leaky vacuum hoses
All suggestions welcome and greatly appreciated!
Mr. Bali Hai