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2004 Forester 2.5 XS
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Discussion Starter #1
I'm posting this on a forum where I know at least someone will respond and help me bounce around a couple of ideas. I tried posting the same question on VWVortex, and plenty of people read it, though no one responded.

My girl has a 2003 Jetta 2.0L Auto. I have been with her long enough to put roughly 6000 miles on the car. Not to over editorialize, the car has been a pain in the donkey, just like all the other VWs I have been worked on.

Right now I'm trying to chase down an intermittent loss of power on the freeway. Typically 65-75mph. Steady throttle, usually catches you sleeping, just cruising, never passing or accelerating onto the freeway. Just loses power like it's run out of gas.

It never stalls, and after usually a 3-10 second pause, power comes back like nothing happened, just long enough to scare you to death in crazy Vegas traffic.

I'm guessing the fuel pump or related hoses. Loss of fuel pressure, while maintaining enough fuel flow to keep the engine running. Anyone care to toss me some ideas? A new fuel pump for this stupid car is a kick in the nuts from a dealer, and not too much better off-brand. Just trying to make sure before I drop a couple hundred and an afternoon under the back seat.
 

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No real scientific basis for anything that follows...

It seems like if you are on the highway then it wouldn't be the fuel pump. The main reason would be that on the freeway it is the most fuel efficient so it would seem that the amount of fuel necessary would be smaller than when, say, accelerating.

I assume you've changed the air filter?
 

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2004 Forester 2.5 XS
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Discussion Starter #3
The car is in pretty much tip-top shape. All services are caught up, I do the work myself. Only 64xxx on the clock.

I can't see an ignition problem that only lasts a few seconds, usually either the coils are working or they aren't Sometimes the power loss is more prominent when less than 1/2 a tank of gas.

Fuel pumps that are going bad will sometimes overheat with steady speeds, it happen on motorcycles, rarely, but I've seen it. They guys at the dealer said the fuel pumps are known to be a little dodgy on these models, even before 75,000 miles.
 

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2017 VW Golf SportWagen 5MT
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If this happens at night, see if the lights dim. Could be a charging system problem, like a bad alternator, weaker spark would make you loose power.

Stan
 

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2004 Forester 2.5 XS
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Discussion Starter #5
An interesting point stan_t. But, the couple of instances that it has occurred at night, I never noticed the lights dimming. The battery is completely strong, and I don't suspect the alternator.

The battery is enough of an electrical buffer in the system, I can't imagine even just a few moments of a lack of charge could cause the power loss I'm experiencing. Also as long as this problem has been occurring, I'd have noticed the battery getting weaker, or other electrical clues to suspect. I believe anyway.
 

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2004 Forester XT Premium 4EAT
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I'm posting this on a forum where I know at least someone will respond and help me bounce around a couple of ideas. I tried posting the same question on VWVortex, and plenty of people read it, though no one responded.

My girl has a 2003 Jetta 2.0L Auto. I have been with her long enough to put roughly 6000 miles on the car. Not to over editorialize, the car has been a pain in the donkey, just like all the other VWs I have been worked on.

Right now I'm trying to chase down an intermittent loss of power on the freeway. Typically 65-75mph. Steady throttle, usually catches you sleeping, just cruising, never passing or accelerating onto the freeway. Just loses power like it's run out of gas.

It never stalls, and after usually a 3-10 second pause, power comes back like nothing happened, just long enough to scare you to death in crazy Vegas traffic.

I'm guessing the fuel pump or related hoses. Loss of fuel pressure, while maintaining enough fuel flow to keep the engine running. Anyone care to toss me some ideas? A new fuel pump for this stupid car is a kick in the nuts from a dealer, and not too much better off-brand. Just trying to make sure before I drop a couple hundred and an afternoon under the back seat.
I highlighted the problem for you. I hear that driving it to the nearest Subaru dealership and trading it in works wonders! :tongue:
 

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2003 Forester
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Sounds like an electrical issue NOT fuel. Intermittent connection somewhere or faulty CPU, now which CPU that's a good question, I have no idea how VW splits up data control.

Try rapping and pushing together all the connectors you can see.


Ron W.
 

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2004 Forester 2.5 XS
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Discussion Starter #9 (Edited)
piead7, I was wondering who would point that out first. Haha. Believe me, if she wasn't so significantly upside down on the value, the car would be gone gone gone by now. She loves my Forester with a passion, and I need something turbo-charged in the worst way.

But since getting rid of the damn thing isn't really an option i the near future, I gotta try to fix this thing.

--No MIL light illuminated, and I've had the dealer do a full electrical system diagnostic, last week in fact. VW runs your standard CAN-bus setup, several local area controllers communicating on a two-wire system, etc. Which would have pointed out any electrical or connectivity issues, but will not see a fuel pressure loss issue. Not to mention they think the fuel pump is suspect--
 

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If the fuel pump was having problems you would notice it most in high load situations. It should basically "sputter" out. Any idea what type of fuel pump system they use? In tank or inline? How does it act at idle and under higher load?

I'd say its more likely to be something in the vacuum system or with some sort of valve.
 

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2004 Forester 2.5 XS
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Discussion Starter #11
Fair enough. Far as I know it's an in-tank fuel pump. Idle is as normal as can be, and high load doesn't typically sputter out. Usually it's just at steady throttle on the freeway, which is higher load on the engine/fuel system in the Jetta vs. the Forester.

I would hope that a spotty vacuum connection, or a sticking valve would happen more regularly than just freeway cruising, and that the dash lights would illuminate indicating an issue.
 

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09 Forester 2.5X
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704 Posts
Clogged cat?

The loss of power sounds like a bad mass air meter, throttle body and rarely the coolant temp sensor ECT. Check these. When cold unplug the mass air sensor and see if the problem still is present. Doing this will turn on the engine light and store a fault. if PROBLEM IS STILL PRESENT THEN LOOK ELSE WHERE.
PS: Im just googling things...but more stuff for you to check out!
 

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2007 FSXT 5MT
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Agreed- Sounds electrical over anything else. Clean the intake and MAF (careful they are TOUCHY). How does the timing belt look?

Also- check the idle stabilization valve and vacuum system as other mentioned.
 

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i am also having problems with my 04 1.8t jetta (manual). my car has lost up to 15 mph on the freeway and it scared me to death since i couldnt get my car to kick up the speed. i tried shifting to neutral, downshifting, and nothing works...it just does it by itself. no one on vortex replied either..actually this is more info than i got out of any other posts.

i've replaced battery, fuel filter, alternator, water pump, serpentine belt, timing belt... all cause it was time, i take care of my car, but this is really driving me nuts especially since it cant be replicated and ive taken it to 2 vw dealers... any other ideas?
 

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2006 Forester XT
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Symptoms....

Those symptoms are exactly the same as my last car.

I had got a tank of bad gas, full of water and rust, nothing small enough to plug the actual fuel filter, but big flakes - on a straight highway, after ten or twenty minutes of steady cruise, the filter sock in the tank would get absolutely clogged off, and the power would just drop and drop, until the car came to a stop.

After the engine stops, the crap falls off and the car is driveable again, but it will happen next time you 'cruise'.

The fuel pump sucks steadily and re-circulates a lot, so as long as the ignition is on, the car is keeping all the crap on the 'sock'. The solution is to pull the pump when the gastank is almost empty, and clean off the sock and the bottom of the tank. Can be labor intensive, but no new parts needed.....

I did a thread on it, here is a pic of the clogged sock....


Due to the design, this pickup cup has a one-way valve, so the crapola gets in, but can't get out.

Guaranteed diagnosis - next time it quits, pull over, turn off the ignition and grab the roof rail, slosh the gas tank side to side and drive away, if your power is back, it's the sock!

Hope that helps......S
 

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i forgot to mention that it always happens while on the freeway, where speeds are 65+, and my car doesnt turn off... i havent paid much attention to the gas tank, although i think the few times i did check it was under 1/2 tank. maybe that's something else i'll relay to the dealer. i've always used premium gas, because of the 1.8t, and almost always use shell (i've noticed it lasts longer and car runs smooth, unlike others).

any other ideas? weird how there's a discussion in a subaru forum and not much happened at the vortex lol.
 

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2004 Forester XT Premium 4EAT
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Sounds like an electrical issue NOT fuel. Intermittent connection somewhere or faulty CPU, now which CPU that's a good question, I have no idea how VW splits up data control.

Try rapping and pushing together all the connectors you can see.


Ron W.
I second the idea of some sort of electrical issue or problem with the charging system.
 

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2010 2.5X Limited
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I have had a very similar experience in a different vehicle, but it turned out to be the coil pack that feed the juice to the spark plugs.
 

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2004 Forester 4EAT
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Coil packs can generally be ohmed out. I have no idea what spec would be, but you will be looking for both primary and secondary readings. Primary is between positive and negative of incoming 12v. (when unplugged) should probably be around 6-20 ohms. The secondary reading is between positive incoming terminal and the spark plug wire terminal. This should be somewhere around 8k - 20k ohms. Check when cold and again when hot. See if one of the coils changes any.
 
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