I have a 03 forester XS 140,000  has been very hot here. was running good down freeway at 70 then i hit passing gear and car started to lose power. Got off freeway and it went down hill from there to a complete stop. I did nurse it home ran like crap 0-10 mph spuutering all the way. I put a new fuel filter on car and took on freeway. going 70 mph i hit the gas and again losing power and surging. I am going to check fuel pressure.. Any ideas from anyone would be great..I guess i will have to ride my Harley to work.

No check engine light?

 

Does it smooth out at higher RPMs and then lose power at low, under load? - That would indicate plug wires.

 

Bucking/surging without explanation or after warm up can be fuel pump.

Update on my subaru..Replaced 02 sensor front bank per code that came up, Also replaced fuel filter. Took on freeway going 70 mph hit passing gear and craps out again? HELP!!!!

No CEL?

Have you checked for codes?

When was the last time it had a full tune up?

yes i had code for 02 sensor front bank..replaced and light went out but car still runs bad when under load

Running bad under load, again I ask when was the last time it had a full tune up, plugs, wires, ALL filters, PCV valve. When was the last time the timing belt was done?

 

What was the code the car threw?

Timing belt..water pump head gasket done 30,000 ago at dealer..tune up been a while also PCV..auto zone paperwork says  bank 1 sensor (H02S11) which has cleared after new 02 installed.. any chance it can be fuel pump? i was going to check pressure.

what about a vacume hose? as my son had problem on his 2005 turbo legacy?

pcv has no ball in it? I just pulled out

It could be so clogged the ball doesn't move.

no i can see right through it..lol..I will buy new one this morning at autozone..there was a big vacume leak there..lol

had wrong valve..looked at youtube for location and guy showed wrong place..i will go find right location..lol

In modern engines the PCV valve really does do tings so if its not working right its worth replacing. I would inspect the spark plugs too and check to make sure all the hoses are tight.

still same problem..did not have to go on freeway just power down and starts surging..replaced 02,fuel filter, pcv valve..I guess plugs next

weird - make sure the breather hoses are routed correctly, make sure you haven't lost the seal/o-ring on the plastic oil filler screw-plug.

 

I once read of an STI that had PCV/breather hoses misrouted after a swap/some work and it affected the oil pressure reading.

 

you may need to arrange to monitor fuel pressure and maybe some other parameters while driving. There are also ways to log with a laptop and rom raider.

yup NGK plugs and fuel pressure next i guess..

Sounds like a similar problem I'm having with an '01 Outback.

All due maintenance has been done by the dealership recently, fuel pump, regulator, filter, plugs, tranny service, etc., timing belt, fluids, all the obvious stuff.

I've had the car in there twice this year. The last time, they kept it for over a week... and they still can only tell me they don't know what's wrong.

I wonder if they missed something?

 

Here's the weird thing... all these problems disappear when the gas tank is full. At about 3/4 tank, they start up again.

 

I've tested this out a couple times now. If I keep the tank topped off, I'm good... but that means I can only travel within a certain radius of my location.

 

Any ideas?

What happens if you get low on gas and remove then reinstall the gas cap?

I'll give that a try, thank you!

 

(That'd be my luck -- something as simple as a gas cap issue.)

Sometimes it is, especially when its repeatable like clockwork.

 

Or the EVAP isnt venting the tank, but gas caps are cheap and a good place to start,

yup NGK plugs and fuel pressure next i guess..

 

 

Is this a pseed dependent issue (always happens at speed) or only when its been running a while then it happens. 

Update: replaced worn out plugs , air filter , same results..Did a fuel pressure test and what do you know it was just a trickel coming out of fuel line after bypass fuel filter and crank key. I think we found the problem as she needed a tune up anyway.Thanks everyone for your help..Also found out there was a filter behind the glove box as i was wondering why the air and heat did not blow  like my outback..Blew out filter and increased volume out of vents by 1/3.

 

JK North Idaho USA

Replace that cabin air filter. It's only $10 to $15. From my experience the Fram fresh air are actually the best w/ baking soda to deodarize,especially if anyone has allergies.

 

Either way those get nasty and can affect your health.

Update: replaced worn out plugs , air filter , same results..Did a fuel pressure test and what do you know it was just a trickel coming out of fuel line after bypass fuel filter and crank key. I think we found the problem as she needed a tune up anyway.Thanks everyone for your help..Also found out there was a filter behind the glove box as i was wondering why the air and heat did not blow  like my outback..Blew out filter and increased volume out of vents by 1/3.

 

JK North Idaho USA

wow, do you have a warranty for that fuel pump? I think you listed it was changed already.

I had replaced fuel filter as i will be replacing fuel pump this weekend.