99 Subaru Legacy Wagon... loss of power and acceleration

[tkt117]

I have a 1999 subaru wagon with 246K miles. The car has been a dream, and has not had any problems other than a bad oil pump and normal maintenance. About 6 months ago the car was experiencing a loss of power and wouldn't accelerate when I pressed the gas. I thought it needed a tune up. After replacing spark plugs the problem persisted. My mechanic is at a loss. He puts in on the diagnostic computer and everything checks out okay. The problem has gotten really bad recently. If I floor the gas the car won't get above 1,500 rpm and sometimes it stalls out completely. If I "tap" the gas peddle I can get the rpms as high as I want.

My mechanic performed all of the obvious test, replaced fuel filter, checked fuel injectors, check engine compression, checked the MAP sensor, replaced the oxygen sensor, replaced the ignition coil, replaced the timing belt. We cannot find the source of the problem.

I have been driving the car for the past six months with this problem, but it is getting progressively worse. Has any one experienced any thing similar. Next we are going to swap out the Mass Air flow Sensor. Beyond that, the only thing we can think of is the computer has a problem.

HELP!!!!

 

[John Gibson]

Ummm .........Blocked catalytic exhaust?
tkt117 wrote:

I have a 1999 subaru wagon with 246K miles. The car has been a dream, and has not had any problems other than a bad oil pump and normal maintenance. About 6 months ago the car was experiencing a loss of power and wouldn't accelerate when I pressed the gas. I thought it needed a tune up. After replacing spark plugs the problem persisted. My mechanic is at a loss. He puts in on the diagnostic computer and everything checks out okay. The problem has gotten really bad recently. If I floor the gas the car won't get above 1,500 rpm and sometimes it stalls out completely. If I "tap" the gas peddle I can get the rpms as high as I want.

My mechanic performed all of the obvious test, replaced fuel filter, ...

 

[tkt117]

My mechanic checked that as well, and he said it was fine. He is really stumped...

 

[Carl 1 Lucky Texan]

tkt117 wrote:

My mechanic checked that as well, and he said it was fine. He is really stumped...

hmmm - seems like it could be low fuel pressure/weak fuel pump or fuel press. regultator. I dunno. try posting this on the 'new generation' forum at www.usmb.net as well.

Carl
1 Lucky Texan

 

[tom klein]

i'm a consumer, and not a mechanic. but i find your use of the word "replaced" rather than "inspected" a little worrisome. some of these parts are expensive, and can probably be tested without being replaced. also, it seems to me that six months to diagnose and fix a problem is way too long.

your mechanic may be honest, but it may be time to get a second opinion, preferably from a "subaru specialist", if you can find one in your area.

otherwise, call it quits after 246,000 miles and get another car - it seems to me like you've gotten your money's worth out of this one.

....... tom klein

On 2005-12-12 21:41:05 -0500, "tkt117" said:

I have a 1999 subaru wagon with 246K miles. The car has been a dream, and has not had any problems other than a bad oil pump and normal maintenance. About 6 months ago the car was experiencing a loss of power and wouldn't accelerate when I pressed the gas. I thought it needed a tune up. After replacing spark plugs the problem persisted. My mechanic is at a loss. He puts in on the diagnostic computer and everything checks out okay. The problem has gotten really bad recently. If I floor the gas the car won't get above 1,500 rpm and sometimes it stalls out completely. If I "tap" the gas peddle I can get the rpms as high as I want.

My mechanic performed all of the obvious test, replaced fuel filter,

^^^^^^^^^^^^^^^^^

checked fuel injectors, check engine compression, checked the MAP sensor, replaced the oxygen sensor, replaced the ignition coil,

^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^

replaced the timing belt. We cannot find the source of the problem.

^^^^^^^^^^^^^^^^^^^^^^

I have been driving the car for the past six months with this problem, but it is getting progressively worse. Has any one experienced any thing similar. Next we are going to swap out the Mass Air flow Sensor.

^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

Beyond that, the only thing we can think of is the computer has a problem.

HELP!!!!

 

[Mortimer Schnurd]

Valve or ignition timing off 1 or more tooth? If it jumped one tooth it will run like that. Poor power and hot. It might start OK and even idle like that

 

[tkt117]

"i'm a consumer, and not a mechanic. but i find your use of the word "replaced" rather than "inspected" a little worrisome. some of these

parts are expensive, and can probably be tested without being replaced. also, it seems to me that six months to diagnose and fix a problem is way too long. "

Sorry... simple matter of semantics. Everything that was replaced on the car had a "below optimum" reading. Much of the work was stuff that needed to be done... ie timing belt, tune up, oxygen sensor. The only other thing that was replaced was the ignition coil which was not putting out as many volts as it was supposed to. So it to was bad. The other items that we checked, we swapped out with another Subaru that was known to work. My mom has a 1996 Outback and many of the parts are interchangeable. So we have been removing sensors and trying through trial and error to find the problem.

The fuel pressure regulator sounds promissing. That may be the next test. It has to be one of these numerous sensors on the car.

"otherwise, call it quits after 246,000 miles and get another car - it seems to me like you've gotten your money's worth out of this one. "

As far as getting rid of the car...I got another 100K + miles left in this baby! I am confident she will go the distance.

Thanks for the pointers... it is very perplexing.

 

[johninKY]

My 95 wagon a few years ago had the exact same problem. Replacing the air flow meter solved it.

 

[lkreh]

It's probably time to try a Subaru dealer. Indie mechanics can be good, but dealer mechanics have probably seen this one before, can diagnosis it, and give you a repair estimate. If you ultimately decide to DIY, the dealer will probably charge you for diagnosing the problem, but that cost will pale in comparison to all the work you've already done chasing the problem.

 

[Michael Pardee]

I have a 1999 subaru wagon with 246K miles. The car has been a dream, and has not had any problems other than a bad oil pump and normal maintenance. About 6 months ago the car was experiencing a loss of power and wouldn't accelerate when I pressed the gas. I thought it needed a tune up. After replacing spark plugs the problem persisted. My mechanic is at a loss. He puts in on the diagnostic computer and everything checks out okay. The problem has gotten really bad recently. If I floor the gas the car won't get above 1,500 rpm and sometimes it stalls out completely. If I "tap" the gas peddle I can get the rpms as high as I want.

My mechanic performed all of the obvious test, replaced fuel filter, checked fuel injectors, check engine compression, checked the MAP sensor, replaced the oxygen sensor, replaced the ignition coil, replaced the timing belt. We cannot find the source of the problem.

I have been driving the car for the past six months with this problem, but it is getting progressively worse. Has any one experienced any thing similar. Next we are going to swap out the Mass Air flow Sensor. Beyond that, the only thing we can think of is the computer has a problem.

HELP!!!!

As expensive as it is, my money's on the MAF sensor. Since "reckoning" mixture is primary and the ECU relies very heavily on input from the MAF, MAF failures too often don't show up as trouble codes. The MAF's too important to be wrong! And the symptoms are not unusual for a bad MAF.

Mike

 

[tkt117]

Problem Solved!

The problem is a bad MAF Sensor, which ironically was recalled THREE WEEKS AGO! When we began looking for the problem the recall wasn't activated for my car. However during that course of time, Subaru has issued a recall and I got my car fixed for FREE! Well the sensor anyway....

I wanted to thank everyone for their input, and especially thank the person who told me to post on the Ultimate Subaru Web Site! They were the ones who informed me that there is an active recall. http://www.usmb.com

So if you have a 1999 Subaru Legacy that is having accelleration and loss of power problems, contact your dealer. You may have a faulty MAF Sensor.

The symptoms are as follows:

Unstable idle speed
Occassional stalling when not in gear.
Constantly high CO ( and lambda voltage) at idle. Should oscillate between lean and rich under normal circumstances.

Cause: MAF Sensor reads too high an air flow on idle, and too low an air flow at high loads. Since the ECU thinks there is more airflow at idle than there really is it pulls too much fuel, causing an overrich mixture which the ECU cannot compensate for sufficiently. Since the ECU thinks there is less air flow on high loads then there really is, it puts out too little fuel, causing a lean mixture. Since ECU runs open loop air/fuel ratios at high loads, AFR compensation is not even attempted.

Remedy: Replace the air flow sensor ASAP. It is not possible to clean these delicate hot film sensors effectively. As the sensor deteriorates, mixtures become leaner, eventually causing damage to the engine due to det and high temperatures. As a short term fix, raise the idle speed, use a high octane fuel and keep engine revs as low as possible while driving.

 

[John O]

Problem Solved!
Thanks for posting this...I'll keep a copy of it in my '99.

-John O