1999 Subaru Legacy -- all of a sudden, engine malfunctioning....

Andrew Gervais
15

Asked by Andrew Dec 27, 2011 at 11:56 AM about the 1999 Subaru Legacy 4 Dr Outback Limited 30th Anniversary AWD Wagon

Question type: Maintenance & Repair

Legacy outback (ltd) engine sounded perfectly fine for months

took on the highway, up to 70 -75 mph, hadn't gone that fast yet
worked fine all the rest of that night

sat in driveway -- in cold weather (20F) that rose to 40 and back to freezing -- for a couple days

after couple days, it starts fine, but after driving 10 minutes, I notice a barely perceptibly stuttering sound with the engine that started to shake the car

got worse as time went on, lower RPMS made it shake much more, higher rpms seemed smoother.

i stopped to check it out, idling made the car shake really bad, engine made a chugging, puttering sound out of the exhaust.

I put a bottle of dry gas in gas tank, in case water in gas tank
I checked oil next day, was low but had some

started car today, cold morning, and car really chugged and shutoff, gave it extra gas and higher RPMS ran smoother, took foot off gas, low RPM idle made engine cut out.

engine has new spark plugs and wires, but this issue seems reminiscent of the spark plug problems I used to have


any advice would be MUCH appreciated! thank you!

3 Answers

Mike Hecker
265

Sounds like a bad air flow meter (mass airflow sensor) or clogged cat convertor. Is the service engine light on? I need to know miles. Is it overheating? does it smell like rotten eggs? Email me subject 99 legacy @ 96sidekick@gmail.com

2 out of 2 people think this is helpful.
Andrew Gervais
15

Thanks for your response, Mike. I took it to the mechanic yesterday, he ran a system diagnostic computer that read cylinders 1 and 3 missfiring, and the knock sensor was reporting something. They said they would want to do a cylinder pressure test to see if the head gasket was bad.... around 120,000 miles headgasket broke and caused overheating, they replaced it with the version that wasn't so faulty as the factory one. they also said it could be the timing belt might have skipped a tooth. car has 237,000 miles, doesn't smell like rotten eggs. thanks!

1 out of 1 people think this is helpful.
Clew_Havness
35

Hey Andrew - this sounds similar to a problem I've been having on my '96 for years and years now. In my case, it seems to be related to O2 sensors. I'm a little hazy on the details, it seems like there are multiple sensors on the engine (I have a '96 Legacy Outback ... don't know which engine size). After taking it to a dealer several times and the problem never completely going away, my local guy replaced one (or more?) O2 sensors and the problem went away for a good long while. It's started to rear its head again, though. Someone who knows more than I will confirm or deny that there are multiple sensors. So I don't know how helpful my response is, but Oxygen Sensors might be something to check.

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