01 forester 2.5 stumble

[DaveT]

Hi all,

 

Our 2001 2.5L automatic forester has a problem.

 

Starts & idles normally. Usually runs (cruises) normal.

 

When "hitting the gas" to get going, the engine stumbles, then "kicks in". Low RPM + open throttle it doesn't like. Once the RPMs get up, it smooths out, seems normal. When driving normally with the auto transmission, each time it upshifts, dropping the RPMs down into the stumbling, until it revs up again.

 

It seems worse when cold.

 

When I pulled back into the driveway, it more does a little skip than a stumble when I tap the gas (in neutral).

 

I read the codes, all I get is 0420 (slow cat / response) (very old news, never could get rid of that one, I'm not buying all oem parts for that, too many $). It's been running fine that way for years.

 

I also have a new code 0303 cylinder #3 misfire.

 

 

Any ideas? I'll have to do the usual plugs & wires, filters thing - probably time for them anyway.

 

 

Thanks,

Dave

[Rooster2]

Replace wires and plugs, since you have a known #3 cylinder misfire. I have a hunch this may fix your problem.

 

Drop us a note, if this fixes, or doesn't fix the problem.

[nipper]

this is easy, it is atuneup and a front O2 sensor. Dont fix the O2 sensor you may never get rid of the stumble.

 

 

 

nipper

[forester2002s]

And do a search on this board for <hesitation>.

There are lots of posts with your same problem.

 

My own solution (2002 Forester 5MT) is to let the car sit for about 10-seconds after start up (not touching the throttle, nor any other electrics), and then to pull away.

I find that if I drive off immediately after starting, then I get the low-speed hesitation that you describe.

[nipper]

I get it the first R to D shift, i never worried or thought about it.

 

 

nipper

[unibrook]

x2 on your front 02 sensor. If it hasn't been replaced in the last 40k miles, that is your prime suspect.

 

The only odd thing in your post is that it is worse when cold.

If front 02 sensor is the culprit, it will only act badly when warm.

 

Cold hesitation may be something diff.

Edited May 10, 2010 by unibrook

[DaveT]

Fuel & air filters had no effect, didn't really expect them to. Plugs & wires ordered. Will Update in a day or 2.

[DaveT]

I got the #1 & #3 plugs & wires changed out, it runs much better now. The old plugs had about .070 gaps!

 

The only reason I haven't got the other 2 yet is time. It really is annoying that they are so buried.

 

2 & 4 get done this weekend.

[DaveT]

#2 & #4 changed out. Seems to have fixed the problem.

 

I had to be very careful removing the plugs, to get them freed up. Turn a little CCW, then CW, for the first revolution or 2.

 

Next time, I'll have to remove them w/ the engine warmed up. No fun to work on that way, but I've found almost any threaded part will come out easier with the engine hot.