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Misfire?


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8 replies to this topic

#1 Shillidincha

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Posted 25 June 2013 - 09:48 AM

I've just bought a 2001 legacy gx 2.5 automatic about 3 weeks ago or so, had some over heating issues, but a thermostat change luckily fixed it, but I'm noticing when I'm driving on the motorway about 60 mph + I can notice that the car seems to be almost misfiring. It comes and goes and only happens when I hold the throttle steady.

The cars got 138000 miles on it, hopefully someone on here can advise me on what they think it may be, I'm hoping someone is going to say spark plugs / wiring loom / or get a terra clean treatment - something relatively easy to sort and NOT head gasket (I know a lot of subarus go at about 150k) / the engines knackared!!

Looking forward to any advice / replies

Edited by Shillidincha, 25 June 2013 - 09:49 AM.


#2 davebugs

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Posted 25 June 2013 - 11:16 AM

Welcome to the USMB.

 

You'll be awful lucky if a thermostat fixed your troubles!  And an OEM thermostat is best.

 

See if it has OEM plug wires.  If not IMO start there.

 

Also folks tend to overspend on spark plugs.  Like if they are Bosch Platinums throw them as far as you can...

 

Those cars have external cooland leaks usually so look where you park for a little fluid.  Actually they usually start on drivers side between cyl 2 & 4 onto the cross member where it's difficult to see.



#3 1 Lucky Texan

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Posted 25 June 2013 - 02:44 PM

12 year old rubber or plastic anything is suspect so, yeah, wires might be the ticket. Somtimes misting them under the hood while idling will show arcing. Could also be some oil in the plug holes from leaking valve cover gaskets I suppose. Has the car been well maintained? How old are the plugs?

 

You might also benefit from a bottle of SeaFoam or Techron in a tankful of fuel. Might clean some carbon out of the injectors/combustuin chamber.

 

at least you have some not expensive 'tune up' type things to try first.


Edited by 1 Lucky Texan, 25 June 2013 - 02:45 PM.


#4 unibrook

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Posted 25 June 2013 - 08:29 PM

Front 02 sensor perhaps?

Does it buck only when warm?



#5 heartless

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Posted 26 June 2013 - 06:34 AM

starting with the basic tuneup items is always a good idea when you dont know the history of a car.

 

  • Sparkplugs - NGK brand as specified in the owners manual;
  • plug wires - these cars are a tad fussy about those, OEMs are best; not sure on the newer stuff, but the NGK brand wires seem to be OK on the older ones. Stay away from cheap parts store brands for sure.
  • new air & fuel filters couldnt hurt
  • PCV valve? they tend to get overlooked and are a maintenance item, altho typically these cause issue under load, not steady throttle...
  • check and replace any hard, dry, brittle vacuum lines - poor vacuum can cause all kinds of funny issues.

Edited by heartless, 26 June 2013 - 06:35 AM.


#6 ivans imports

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Posted 26 June 2013 - 10:24 AM

Howbout somthing easy like droped ex valve guides the unhappy side of overheating can be checked by looking up the ex port and see if guides are were thay should be about 1/4 inch below head casting. Or bad plugs or wires any oil on plug boots ?



#7 Shillidincha

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Posted 26 June 2013 - 10:43 AM

Thanks guys, the guy I bought it from said he maintained it very well and it came out of its MOT the day I collected it and it passed with minor advisories ( nothing engine related).

Front 02 sensor perhaps?
Does it buck only when warm?


Yes it does, normally motorway - or highway ( I'm guessing some of you guys are American) speeds, I can only best describe it as like a cough, the car still drives but its really irritating!

Well thanks a lot guys for your help so far, I'll get changing the suggested items and see if that makes a difference (hopefully it does)!!

#8 ivans imports

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Posted 26 June 2013 - 10:48 AM

+1 front 02



#9 timintc

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Posted 02 July 2013 - 09:30 PM

check your overflow tank with the engine idling if there are bubbles its likely a head gasket leak. Subaru thermostats like subie starters, water pumps, alternators etc etc are usually pretty reliable and long lasting. The fact that you already experienced an overheating episode makes me lean towards head gaskets since we see so many of them up here in Northern Michigan. My theory is that you may have coolant leaking into your cylinders as you drive causing your performance issues. but then again it could be any of the other possibilities offered here, but check your overflow first and eliminate the dreaded HG issue.






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