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2000 outback, rough idle, check engine light, bad mpg

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I just bought a 2000 outback limited wagon with manual trans and so far, I haven't gotten more than 15mpg out of it. It idles rough until it gets up to operating temp, then smooths out for the most part. The plugs, wires, and air and fuel filters were replaced just before I bought it about a month ago. The check engine light has been on for a couple weeks now, but when hooked up to a diagnostic computer, it doesn't show any codes. Anyone else have a similar problem? Are there any common issues with temperature sensors?

 

Thanks for any help

Brandon

My brothers OB wagon 5 speed has the same issue. The mechanic said it has burnt valves. His needs new heads, or a new engine.

Get a better computer.

 

This is getting frustraiting

 

*vent alert*

 

We need the mileage on the car to help tell you whats wrong with it!

 

*vent alert over*

 

 

Disconnect the battery for ten minutes see if the codes clear, then when the CEL comes back on, get the codes read. Right now you probably have multiplee codes in there.

 

nipper

Suggest opening the hood, check to see if the plug wires look new? If they look old and dirty, then maybe the plugs and wires were never changed. Rough idle and poor gas millage is a sure sign that combustion is poor.

 

Pull the codes, as someone said, is a good first start to diagnosing the problem.

  • Author

My bad on not posting the mileage; 170,000

 

The plugs and wires are definitely new, I watched the guy change them before he sold me the car.

 

I'll try another computer and see what comes up.

 

Thanks all of you for your help,

Brandon

!70 can be timing belt, O2 sensor, who knows what else.

 

Get the codes so we can have a starting point.

FWIW, I cleaned my MAP/ ITS, IAC, replaced my PCV valve, and the hose leading to it. It smoothed the idle out and (knock on wood) the CEL that had a cat code has been out for 4 days.:clap:

  • Author

Okay, I ran the codes on another computer and all I got was Cylinder 1,2, and 4 misfire.

What brand of wires?

 

are the spark plug wire ends soaked in oil?

 

What kind of plugs?

 

Can you run the car at night, and with a spray bottle wet the ignition wires and look for sparks?

 

nipper

  • Author

NGK plugs and wires.

 

And there actually is a little bit of oil on the plug wire boots closest to where it connects to the wires, just on the inside of the shroud on the boot, and it looks like it could easily trail down to the spark plug. hmm...

 

sprayed the wires with a spray bottle while running in the dark, didn't see any sparking.

 

Thanks again for your help nipper and everyone else.

Valve cover/bucket leaks will cause misfires like you are seeing. The oil attracts humidity and also breaks down the wire insulation.

  • Author

That makes a lot of sense. Is it possible that as the engine warms up, the oil/ moisture will burn off/evaporate causing the sputtering to go away?

That makes a lot of sense. Is it possible that as the engine warms up, the oil/ moisture will burn off/evaporate causing the sputtering to go away?

 

 

yes.

  • Author

Awesome! I'll get to work on that ASAP! Thanks for your help and quick responses, nipper!!

 

Brandon

I have been wrong before, but thats my best guess.

 

 

nipper

I believe the that the all too common Misfire codes in these 2000 outbacks is caused by noise interference between plug wires, and injector wires. They routed them WAY too close to toghether.

 

Make sure that none of the injector wires are actually touching the plug wires. sperate the 2 as much as you can. I've eliminated this reoccuring code by placing flexible wiring conduit around the injector wires, as well as the factory conduit that SHOULD have been swapped onto the new plug wires.

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