2002 2.5L Loses Power Up Steep Grades

[joesauer]

I have a 2002 Outback Wagon with 2.5L and about 90K miles. Car runs great nearly all the time - except at highway speeds when negotiating a steep grade. I can cruise along at 65 MPH on flat or modest grades all day long. On a steeper grade, as I begin to slowly increase throttle to maintain speed, engine power begins to drop off rapidly, followed by increasingly violent detonation.

 

The first time this happened, the detonation came in so rapidly and violently I thought the rapping was mechanical, and I imediately backed off the throttle thinking somthing was coming apart. Now, if I feather the throttle, I can try and keep the detonation down, but this usually results in speed loss to below 45 MPH.

 

The other solution is to go W.O.T. and force a downshift - but even when I do that, if the detonation has already begun, there will still be milder detonation after the downshift and at the higher RPM. There is also a terrible whistling at the higher RPM - almost like a belt squeal, but since I can change pitch with throttle position, sounds more like something induction related.

 

Once I am back on flat plain, or heading down hill, engine runs fine again until the next steep grade.

 

Other factors that may be important:

 

- Had timing belt changed by dealer about 5,000 miles ago - I noticed problem about 1500 miles ago.

 

- Not getting any check engine indicators.

 

- Very difficult to get converter to unlock under this type of load - which could be worsening the problem.

 

Thanks!

[nipper]

I have a 2002 Outback Wagon with 2.5L and about 90K miles. Car runs great nearly all the time - except at highway speeds when negotiating a steep grade. I can cruise along at 65 MPH on flat or modest grades all day long. On a steeper grade, as I begin to slowly increase throttle to maintain speed, engine power begins to drop off rapidly, followed by increasingly violent detonation.

 

The first time this happened, the detonation came in so rapidly and violently I thought the rapping was mechanical, and I imediately backed off the throttle thinking somthing was coming apart. Now, if I feather the throttle, I can try and keep the detonation down, but this usually results in speed loss to below 45 MPH.

 

The other solution is to go W.O.T. and force a downshift - but even when I do that, if the detonation has already begun, there will still be milder detonation after the downshift and at the higher RPM. There is also a terrible whistling at the higher RPM - almost like a belt squeal, but since I can change pitch with throttle position, sounds more like something induction related.

 

Once I am back on flat plain, or heading down hill, engine runs fine again until the next steep grade.

 

Other factors that may be important:

 

- Had timing belt changed by dealer about 5,000 miles ago - I noticed problem about 1500 miles ago.

 

- Not getting any check engine indicators.

 

- Very difficult to get converter to unlock under this type of load - which could be worsening the problem.

 

Thanks!

 

What happens when you manually downshift the car? The pinging under load, sounds like a dead knock sensor, though it has a really wierd way showing up.

 

nipper

[joesauer]

What happens when you manually downshift the car? The pinging under load, sounds like a dead knock sensor, though it has a really wierd way showing up.

 

nipper

 

 

I actually have not tried that - but I am on my way out now for a 120 mile drive - I will try and see what happens.

[ron917]

A bad catalytic converter can cause power loss symptoms as you described. If it is clogged, or if the core is loose and blocking the outlet, exhaust flow can be impeded. I've had it happen in two cars.

 

Bang on the catalytic converter (when cold, don't burn yourself). If it rattles, sounding like there are rocks inside, it's a problem.

[nipper]

Your going to have to untill this is fixed. You really dont want to lug tthe engine to the point where it pings. That is very very BAD knocking, not ping, and can do damage to the engine.

 

 

nipper

[Skip]

Joe says

"There is also a terrible whistling at the higher RPM - almost like a belt squeal, but since I can change pitch with throttle position, sounds more like something induction related."

 

Could at this early age a cat be getting plugged

and the whistle

is exhaust gas coming out of a system leak ?

 

Would this back pressure cause pre-ignition?

[nipper]

Joe says

"There is also a terrible whistling at the higher RPM - almost like a belt squeal, but since I can change pitch with throttle position, sounds more like something induction related."

 

Could at this early age a cat be getting plugged

and the whistle

is exhaust gas coming out of a system leak ?

 

Would this back pressure cause pre-ignition?

 

It prevents the engine from revving freely, also can cut odd the top rpms of the engine. a clogged exhaust can reduce engine vacum, and the computer uses engine vacum to determine load.

 

Check your exhaust systerm. What happens when you floor the car on flat ground...

 

nipper

[ron917]

When my old Volvo had a plugged cat, it did ping on hills when it was acting up. Mine got to the point where it would barely move on a hill. The temp gauge would climb, I guess the engine got hot enough to cause pre-ignition.

 

The catalytic converter core had broken up, and there was big chunk that could block the exhaust outlet. When it acted up, I could stop the car and bang on the cat with a something (e.g., jack handle) to temporarily clear it.

 

For a short term fix, I removed the cat, broke up the core with a steel bar and dumped it out. Of course, I had to install a new one in order to pass the emissions test.

[joesauer]

Thanks to everyone who has answered my thread..

 

Just returned from 120 mile jaunt. As usual, car is awsome on flat or mild grades - everyone was flying tonight, so I averaged 65 to 80 MPH the whole way. Acceleration while pulling into fast lane was fine - nice and snappy. I almost thought problem disapeared.

 

Until fairly steep grade about 1/2 mile long... As usual, RPM started to drop, and detonation commenced. This time, backing off throttle only helped until car began to slow, then detonation started in again - backed off throttle more, car slowed more, detonation eventually started back. I eventually made it over the top at about 30 MPH in the climbing lane.

 

So once the problem begins, it is very sensative until the load is removed. After about 1/4 mile of downhill, everything "reset" and returned to normal.

 

BTW - first run on new Bridgestone G009's, which I purchased this morning based on Subaru owner feedback at tirerack.com. I agree that these are great tires on dry - can't wait to try in the snow..

[nipper]

and manually downshifting did what?

 

nipper

[joesauer]

and manually downshifting did what?

 

nipper

 

Manually downshifting acts exactly the same as when I force the automatic downshift by punching WOT. Although the RPM increases as normal, the reduced load on the engine only reduced detonation - does not elminate it - and with the increased RPM there is still that loud whistle that sounds induction related.

[joesauer]

I have not been under the car yet - anyone have a PDF of the exhaust system, or is there a source for on-line manuals to purchase?

 

From what I am reading, looks like there are 2 cat converters (front & rear) on this model?

 

Thanks Again!

[Richard1296]

Don't just look at the converters, any obstruction in the exhaust system

will cause the same symptoms. An exhaust pipe that is partially mashed

shut or even a muffler that has failed inside is still a blocked

exhaust system. The cats years ago used to be real bad for coming

loose inside and rattling,blocking the exhaust. Converters have improved a

lot but the possibility still exists. A seriously overheated or a lean

engine can also melt the ceramic in converters causing them to block

the exhaust.

If you have access to a heat/temperature gun. Look for the hottest

place in the exhaust system .

The whistleing noise could also be a vacuum leak under the hood.

And vacuum leaks can seriously lean an engine and make it ping.

Of course the lean engine could then make the exhaust so hot it will

damage the converter, so the possibility of more than one repair

may be needed.

But a pinging engine is one that needs prompt attention, or a new

engine will be needed.

 

Richard

[brus brother]

Any chance fuel pickup related? Earlier post on related question suggested trying reverse up steep hill to see if problem occurs as fuel delivery would be gravity fed. If not a problem then fuel delivery is suspect.

[WoodsWagon]

High speed under load is the highest demand for fuel. If your fuel filter is badly clogged, or if your pump is dying, the fuel rail pressure would drop off, the flow through the injectors would reduce for the same pulse width, and the engine would run lean, leading to detonation. Replace the filter, it's easy, and a 90k might as well, and see if it helps.

[OB99W]

I have a 2002 Outback Wagon with 2.5L and about 90K miles. Car runs great nearly all the time - except at highway speeds when negotiating a steep grade. I can cruise along at 65 MPH on flat or modest grades all day long. On a steeper grade, as I begin to slowly increase throttle to maintain speed, engine power begins to drop off rapidly, followed by increasingly violent detonation.[...]

My first reaction upon reading your description was "that could be from a partial exhaust restriction". After reading the follow-up posts, I thought "okay, there seems to be somewhat of a consensus". The fact that the problem shows on steep uphill grades could be due to the increased engine load, or possibly that a loose cat core or muffler baffle is shifting due to the angle of the car. Going downhill would of course lessen the load, and possibly shift obstructing material in the opposite direction, re-opening the exhaust.

 

Although timing, vacuum (leaks) and fuel-delivery problems can cause some similar symptoms, I'm tending to agree with the others who've mentioned the exhaust system; I'd look there first (the whistling sound is what leads me away from the areas of timing or fuel). If there are no obviously collapsed pipes and/or rattles when banging the cat or muffler, a vacuum gauge can be used to help check for restrictions. Also, there are gauges for checking backpressure directly; often they can be attached by temporarily removing O2 sensors and using their fittings. Of course, if an obstruction is developing due to something shifting when going uphill, it might be harder to detect when the car is level.

[skizix]

Any chance fuel pickup related? Earlier post on related question suggested trying reverse up steep hill to see if problem occurs as fuel delivery would be gravity fed. If not a problem then fuel delivery is suspect.

 

Holy cow, would that really work? Seems it'd have to be some kind of crazy steep hill to actually get the gas tank above the level of the injectors. Or am I missing something here?

[brus brother]

Alls I know is what I reads in the funny papers... The following link is the one I was referencing. Keep us posted.http://www.ultimatesubaru.org/forum/showthread.php?t=9821

Holy cow, would that really work? Seems it'd have to be some kind of crazy steep hill to actually get the gas tank above the level of the injectors. Or am I missing something here?

[nipper]

I'm not completely sold on the cat, as the cat would do it on level ground at the same engine rpm, but its a possability. Todays car run so lean, that if they run any leaner, the cylinder wouldnt fire. A clogged fuel filter would really show up on acceleration, of which hes not complaing about (or did he not mention same problem accelerating to get on the highway). When in doubt, lest start with the cheapest thing first. Rent or buy a scangauge or scan tool. Drive the car and watch the ignition timing. Make sure the knock sensor is working.

Here is one, if the cat is clogged, why is it not throwing a CEL. Does your CEL work? Check for codes. If the Cat is clogged that means its dead and you should get a CEL.

I just want to rule out everything else before we say it needs a cat or exhaust system.

 

nipper

[joesauer]

I'm not completely sold on the cat, as the cat would do it on level ground at the same engine rpm, but its a possability. Todays car run so lean, that if they run any leaner, the cylinder wouldnt fire. A clogged fuel filter would really show up on acceleration, of which hes not complaing about (or did he not mention same problem accelerating to get on the highway). When in doubt, lest start with the cheapest thing first. Rent or buy a scangauge or scan tool. Drive the car and watch the ignition timing. Make sure the knock sensor is working.

Here is one, if the cat is clogged, why is it not throwing a CEL. Does your CEL work? Check for codes. If the Cat is clogged that means its dead and you should get a CEL.

I just want to rule out everything else before we say it needs a cat or exhaust system.

 

nipper

 

Hey nipper;

 

Since this is my wife’s car (heavy emphasis on “family responsibility”) I have gone ahead and made an appointment with the dealer. I don’t have any specific concerns with the dealer, but as I was once owned a Mercruiser Marine dealership, I understand the “flat rate” mentality from the inside. We were never able to embrace this in our shop – and I let my head mechanic spend as much time as necessary speaking directly with customers, especially on the hard to diagnose problems. The stuff I would see going on at other dealers is what makes me scared!

 

The other plus is that the dealer gives us a free loaner – usually a fairly new Legacy, or something they would like us to “trade up” to.

 

But not wanting to go in blind, I went ahead and replaced the fuel filter (and for good measure, air filter) this morning. Although I am a big fan of factory parts, being Sunday, Purelator brand was the only thing I could get.

 

After testing, I was about to write nearly the exact same thoughts that you just posted (about running so lean for fuel economy, that any problems tipping towards to the “lean” side could cause what I am experiencing).

 

It looks like the fuel filter was the original – and changing did have a positive effect. Before changing, I could make detonation on “back road” driving if I tried. For example, if climbing a hill, and I accelerated as much a possible just before the trans would down shift, it would mildly ping.

 

After the change, I spent 30 minutes on hilly roads around my house – steep hills, with 20 MPH speed limits – much more severe that anything on the freeway. I could not make the thing ping whatsoever. I hammered on it from standing start, feathered throttle to try and force ping – nothing. The thing ran great.

 

So onto the freeway – 70 to 80 MPH flawlessly – until the first uphill grade. I backed down to very constant 65 MHP, then very slowly began to accelerate – and immediately my old nemesis detonation was back in full force. Now, however, I can recover just by backing off the throttle (where before I needed to drop down to 30 MPH, limp over the hill, and then it would recover).

 

My conclusion is that there was some fuel starvation, which needed “recovery” time to refill / catch back up again (like with a carb, when needle and seat is partially clogged, and you run the bowl dry while hammering – once the bowl fills back up, modest driving is back to normal).

 

So would you agree that at the speeds I am still having trouble, the fuel and ignition maps are probably set the leanest possible to maximize highway mileage?

 

Before I go further, can you tell me if there are useful codes to read from the ECM even though there is no CEL? (Apart from watching the timing as you mentioned - and yes, the CEL bulb lights when key turned on!).

 

Thanks for all the help!

[nipper]

Hey nipper;

 

Since this is my wife’s car (heavy emphasis on “family responsibility”) I have gone ahead and made an appointment with the dealer. I don’t have any specific concerns with the dealer, but as I was once owned a Mercruiser Marine dealership, I understand the “flat rate” mentality from the inside. We were never able to embrace this in our shop – and I let my head mechanic spend as much time as necessary speaking directly with customers, especially on the hard to diagnose problems. The stuff I would see going on at other dealers is what makes me scared!

 

The other plus is that the dealer gives us a free loaner – usually a fairly new Legacy, or something they would like us to “trade up” to.

 

But not wanting to go in blind, I went ahead and replaced the fuel filter (and for good measure, air filter) this morning. Although I am a big fan of factory parts, being Sunday, Purelator brand was the only thing I could get.

 

After testing, I was about to write nearly the exact same thoughts that you just posted (about running so lean for fuel economy, that any problems tipping towards to the “lean” side could cause what I am experiencing).

 

It looks like the fuel filter was the original – and changing did have a positive effect. Before changing, I could make detonation on “back road” driving if I tried. For example, if climbing a hill, and I accelerated as much a possible just before the trans would down shift, it would mildly ping.

 

After the change, I spent 30 minutes on hilly roads around my house – steep hills, with 20 MPH speed limits – much more severe that anything on the freeway. I could not make the thing ping whatsoever. I hammered on it from standing start, feathered throttle to try and force ping – nothing. The thing ran great.

 

So onto the freeway – 70 to 80 MPH flawlessly – until the first uphill grade. I backed down to very constant 65 MHP, then very slowly began to accelerate – and immediately my old nemesis detonation was back in full force. Now, however, I can recover just by backing off the throttle (where before I needed to drop down to 30 MPH, limp over the hill, and then it would recover).

 

My conclusion is that there was some fuel starvation, which needed “recovery” time to refill / catch back up again (like with a carb, when needle and seat is partially clogged, and you run the bowl dry while hammering – once the bowl fills back up, modest driving is back to normal).

 

So would you agree that at the speeds I am still having trouble, the fuel and ignition maps are probably set the leanest possible to maximize highway mileage?

 

Before I go further, can you tell me if there are useful codes to read from the ECM even though there is no CEL? (Apart from watching the timing as you mentioned - and yes, the CEL bulb lights when key turned on!).

 

Thanks for all the help!

 

The purpose of the ECU maps is to keep the car at the ideal stochiometric ratio at all times and all conditions. Its no differnt for highway then sitting in your driveway.

 

I would look at the output of the 02 sensors. One of those really should be throwing a code. It's odd that the second one isnt throwing a hissey fit, since that one measures cat efficency.

 

nipper

 

PS good news is that if it is a cat it may be under thw 100,000 mile warrenty for emissions.

[joesauer]

Hello All;

 

Good news - this problem is solved!

 

Had a great experiance with dealer - they read the ECU, and while there were no trouble codes, the front O2 sensor was outside of spec. So one 22791AA00A O2 sensor ($79.48) and diagnosis & installation ($165.00) and I was on my way to testing (which turned out A-OK).

 

Considering we got to drive an '07 Legacy for the day at no chage while they did the daignosis and repair, I would say that this was more than a fair deal.

 

Thanks again to everyone for their input on this!

[nipper]

Hello All;

 

Good news - this problem is solved!

 

Had a great experiance with dealer - they read the ECU, and while there were no trouble codes, the front O2 sensor was outside of spec. So one 22791AA00A O2 sensor ($79.48) and diagnosis & installation ($165.00) and I was on my way to testing (which turned out A-OK).

 

Considering we got to drive an '07 Legacy for the day at no chage while they did the daignosis and repair, I would say that this was more than a fair deal.

 

Thanks again to everyone for their input on this!

 

YAY see i knew you didnt need a cat

 

nipper

[joesauer]

YAY see i knew you didnt need a cat

 

nipper

 

I am happy about the no CAT replacement as well....

 

Just out of curiousity - I looked all over the web for info on 100,000 mile warranty on emission gear, but couldn't find anything. I believe that Subaru quotes 80K miles or 5-years on a 2002. Is this a Federal mandate type of thing? (I have not looked through the glove box for info yet).

[iluvdrt]

You said you had your timing belt done about 5000 miles ago.

 

Would it be possible one of the cams has jumped a tooth? 1 tooth off on the right intake/exhaust cam wouldnt throw a code, and it would make the car run like crap.