[jubileekr]

Hello,

I am new to here. I found this site while I was struggling with the problem that my car has. But I will try to learn a lot from this forum.

I have a 2003 forest X with a mileage of 96,000. It's been a great experience with this one, since I live in a mountain in SoCal where a lot of snow comes.

From one or two weeks ago, my car began to lose power. With the same driving habit, rpm became higher than usual when the A/T changes its gear (up to 3000rpm). Recently I changed spark plugs, engine oil, and I changed fuel filter, front differential fluid, and transmission fluid last summer. There was no 'check engine' signal. My local mechanic suspected that catalytic converter could be a problem. But a local dealership said they could not find any issue. But I surely feel the difference. What's your opinion? Should I cope with this since this is not a big issue, or should I find a third opinion?

 

[2.5x_sleeper]

I see this is your post, so welcome to the forum from Oregon!

Has your gas mileage changed... decreased? Any hesitation or backfire?

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

 

[jubileekr]

Well, I didn't check the mileage, but I don't see any prominent change. There is no hesitation nor backfire, just engine became a bit louder and shakier.

Thanks.

 

[2.5x_sleeper]

Were the spark plugs changed at 30, 60 & 90K miles?

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

 

[jubileekr]

I don't have any record on previous changes of spark plugs, but perhaps not. I bought this one from a private party. At around 95,000 miles, my car began to lose power and it became shaky, so with some web surfing, I suspected that spark plugs could be a problem and brought it to a local mechanic, and the problem was solved. Well, I am sensitive, so I felt tiny difference between normal operation with previous plugs and new plugs, but I think that is not a big deal. The similar symptom came out after 2 months, but both a local mechanic and a dealership think spark plugs are fine.

 

[2.5x_sleeper]

Hmmm...

• No CEL.
• No decrease in mileage.
• No hesitation or backfires.
• Spark plugs were changed.

I'd be tempted to say your Forester is running as it should. :wink:

Curious... why did your local shop feel the CAT was bad?

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

 

[neoshi]

loss of power can occur when a cat falls apart and prevents proper exhaust flow. but the test to prove that is usually $$$ unless you have physical pieces of it dropping out of the mid pipe when you take it apart.

 

[GoSubieGo]

Perhaps a bad ignition coil and wires, in need of throttle body cleaning, lazy oxygen sensor, tps sensor adjustment, knock sensor failing, or fuel pump issues.

 

[jubileekr]

There is some whistle noise from the exhaust system but the mechanics don't seem to worry about it. I was once stranded in a snow and a truck pulled it out. I don't think that could have affected the CAT.

 

[jubileekr]

Yesterday, I dropped by the dealership and changed rear diff. fluid. Then, the problem was gone!! I don't know the exact connection between the lack of power in the engine and the rear diff. I remember there was a burning smell before but I could not identify where it came from. Now it seems to be gone. I am so happy and thank you guys for your valuable comments.