Surging while accelerating

[kevinsUBARU]

Hi all,

 

I have a 2001 Legacy wagon, 5-speed. It got a new clutch at about 58K shortly after I acquired it; the car has 85K on it now.

 

I left it parked with a half tank at the airport for 5 days. Temperatures were around 30F the whole time I was gone.

 

I get in it, crank it over, and it sputters to life. The idle is smooth, so I think whatever, it's just cranky. I have never had a problem starting it before.

 

No check engine light. Shifts fine until I get back into my city an hour later, and I notice that in load situations (heavy acceleration, hills, ect) the car seems to "bounce" like a rubber band.

 

Four days go by, and the rubber band effect goes away, but the sputtering start in the morning is still there everyday. I fill up with gas two days ago.

 

The rubber banding came back this morning while driving around town. The RPMs jolt in harmony with the car surging, like the clutch is slipping for a split second and then grabbing suddenly. Still no check engine light.

 

Whether it's related or not, when using engine braking in 5, 4, or 3 especially, I can hear a "pepper grinder" sound, not to be confused with the heat shield rattles.

 

Maintenance history (the brief):

 

I put new NGK plugs and OEM fuel filter in at about 50K. Headgaskets were replaced at 60Kish miles, as was the timing belt and various seals.

 

Although I think it has nothing to do with my problems, I'll mention that I have snow tires on, have a kartboy short shifter with bushings, and an USDM STi transmission mount..not a stiff as hell GroupN STi mount.

 

Any ideas?

[Suzam]

I had a 95 auto that did something similar and it turned out to be a bad knock sensor retarding and advancing the timing to compensate for a false knocking it was registering.

[kevinsUBARU]

Interesting. Did you get a CEL?

 

We got 6-8" of snow last night. It didn't do it this morning, but it did this afternoon. I'm pretty sure it's not the clutch...I can't start it in 3rd, and if I punch it in 5th or 4th, the car just bogs.

 

Thanks for the suggestion.

[Suzam]

Never a CEL, I noticed it mostly on inclines applying half or more on the accelerator to speed up or maintain speed. Jealous of the snow, want to head to New England now instead of Feb.

[WAWalker]

Have the plug wires be replaced? Carbon tracking on the plugs/wires can cause a misfire on accel, without setting a misfire code.

 

A bad front A/F ratio sensor can cause this type of drivability problem also.

[kevinsUBARU]

Suzam: Sounds like my problem to a "T".

 

Walker: Plug wires have never been replaced. Perhaps I should do that and plugs at the same time? It's probably due anyhow...

AF ratio sensor cheap/easy to replace? How would I know if that was the problem?

[WAWalker]

If there are carbon tracks on the spark plugs, the plugs and wires will both need to be replaced.

 

Easyest way to tell if the A/F ratio sensor is bad is to watch the fuel trims on a scan tool while driving.

 

Actually I just realized that you said you have a 5-speed. Your car should have a regular O2 sensor. I don't see as many problems with the O2 sensors as the A/F ratio sensors. Still a possiblity, but check the plugs and wire first.

[Rooster2]

Hi all,

 

I have a 2001 Legacy wagon, 5-speed. It got a new clutch at about 58K shortly after I acquired it; the car has 85K on it now.

 

I left it parked with a half tank at the airport for 5 days. Temperatures were around 30F the whole time I was gone.

 

I get in it, crank it over, and it sputters to life. The idle is smooth, so I think whatever, it's just cranky. I have never had a problem starting it before.

 

No check engine light. Shifts fine until I get back into my city an hour later, and I notice that in load situations (heavy acceleration, hills, ect) the car seems to "bounce" like a rubber band.

 

Four days go by, and the rubber band effect goes away, but the sputtering start in the morning is still there everyday. I fill up with gas two days ago.

 

The rubber banding came back this morning while driving around town. The RPMs jolt in harmony with the car surging, like the clutch is slipping for a split second and then grabbing suddenly. Still no check engine light.

 

Whether it's related or not, when using engine braking in 5, 4, or 3 especially, I can hear a "pepper grinder" sound, not to be confused with the heat shield rattles.

 

Maintenance history (the brief):

 

I put new NGK plugs and OEM fuel filter in at about 50K. Headgaskets were replaced at 60Kish miles, as was the timing belt and various seals.

 

Although I think it has nothing to do with my problems, I'll mention that I have snow tires on, have a kartboy short shifter with bushings, and an USDM STi transmission mount..not a stiff as hell GroupN STi mount.

 

Any ideas?

 

 

 

I left it parked with a half tank at the airport for 5 days. Temperatures were around 30F the whole time I was gone.

 

I wonder if you have some water condensation in the gas tank, or may have gotten some bad gas contaminated with water.

 

Suggest you add a can of "dry gas" product to the gas tank. Maybe this will help, certainly couldn't hurt.

 

Also, like you say, it can use a set of plug wires with 85K miles on the odo.

[kevinsUBARU]

8 more inches of snow last night.

 

Started it up today, and it was definitely missing. While I was clearing the snow off, the check engine light starts to blink.

 

With temps forcast to go to single digits, there's no wrenching in the street this week.

 

My favorite repair shop is closed until next monday unfortunately. I've got $200 worth of subie bucks to spend at the dealer, so that should make it a little less painful:)

[Suzam]

Good thing you have the chance to get it in now instead of right beore the holidays, you could have ended up waiting several extra days.