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1997 Legacy gt 2.5 rought idle


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I have a 1997 legacy gt sedan with the 2.5. I have replace the head gasket already. The motor has been running rough before i fixed the head gasket. engine codes of misfire # 4 cylinder and sometimes #2 misfire.Codes have shown up and low and high RPMs. I have put new plug wires and plugs in it. Check the vac lines and they seem ok. Also installed a new pvc valve and cleaned the tubes. It seems to run good at higher speeds. I have also failed inspections due to sensors coming up not ready when DMV hooks up to the the cars computer. Any help on what causes the problem or do i need to take it to the dealer?

 

thanks Joe

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Subaru wires and proper spark plugs?

 

Spray the engine with a water bottle while its running, in the evening. Look for stray voltages (blue sparks) especially around the coil towers.

 

The next possability is a leaking injector. Right now I think its going to be a coil issue.

 

What was done when the HG was replaced.

 

nipper

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Have the codes pulled, and let us know what it says. Failing inspection can be that you went for inspection too soon after having the battery disconnected. It takes a specific number of cycles for the test to be valid.

 

There are a few things it can be, but i really dont want to have you start throwing more parts at it without us first looking at the codes.

 

 

nipper

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If you specifically got #2 and #4 misfire codes, which I think would be P0302 and P0304, then maybe try NGK spark plugs with OEM spark plug wires (not plug wires from an auto parts store).

 

I have also failed inspections due to sensors coming up not ready when DMV hooks up to the the cars computer.
Yes, these are probably the emissions/inspection monitors. There are about 7 of these systems. The longest to set seems to be the evap system. It can take a number of trips over a number of miles to get them all to set to 'ready'. When you get or clear a CEL/MIL or disconnect the battery, the monitors all go back to not ready. There's some info on endwrench.com about it. If you have a reasonable scan tool, it will tell you the status of each I/M. Also if the CEL/MIL is presently on you will probably not pass inspection either, at least that's how it is in NY.
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Nipper

I tied your water test and no problem. I'm getting PO304 code all the time and some times PO302. I spayed carb cleaner around all the gaskets to check for leaks all clear on that.

Dickensheets

Happens warm and cold

xrturbo

Yes i did

 

the guy at DMV said the same that i have to drive it for a few to reset those codes.

 

thanks again Joe

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what plugs and wires did you use?

if you didn't use NGK plugs and Subaru (or Magnecor) ignition wires, then that could very easily be your problem. EJ motors are freaks, do not use aftermarket wires on them. i've seen brand new wires right off the shelf cause misfire codes on EJ motors. installing Subaru or Magnecor wires is the solution.

 

make sure all the wires are seated properly. and find an ignition coil to swap out. it's easy, only takes a couple minutes and you can easily find used ignition coils for sale for not much money. get one and swap it out.

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I was tinking valves also. Did you have a very close look at the valves when you replaced the gaskets? Maybe you should do a compression check to see if the roughness is not caused by compression differences between the cylinders.

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I was tinking valves also. Did you have a very close look at the valves when you replaced the gaskets? Maybe you should do a compression check to see if the roughness is not caused by compression differences between the cylinders.

Heads where rebuilt by a machine shop

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  • 2 weeks later...

Ok, I have installed NGK plugs and factory wires and now the problem is worse constant P0302 and P0304. I guessing it must be the coil. I did have the same problem before motor was rebuilt. Any other suggestions. As for the cam adjustment the cams are installed after the heads are installed and i followed the recommendations of my local Subaru dealer.

 

thanks again

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Thats where i would look first. Without an oscilloscope i cant tell you which, but my gut says coil (keeping in mind my gut was just ripped open so it may be out of cal :-p )

 

nipper

 

 

I'll pick up a new coil tomorrow at the dealer(yes they are cheaper than Auto store) and see if that is it.

 

thanks again

 

Joe

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  • 2 weeks later...
Been awhile but finally installed a new coil from the dealer and still have a rough idle and PO304 code. So far the code is only coming up at idle. Any more help would be appreciated.

 

thanks Joe

 

 

SO there was some improvement.

 

Are we sure the timing belt is on properly.

 

Next to look at it would be vacumme leaks.

 

Is the missfire roving or all the time?

 

nipper

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As for the cam adjustment the cams are installed after the heads are installed and i followed the recommendations of my local Subaru dealer.

 

thanks again

 

What do you mean exactly by this statement? You set the valve lash at .008 intake and .010 exhaust?

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SO there was some improvement.

 

Are we sure the timing belt is on properly.

 

Next to look at it would be vacumme leaks.

 

Is the missfire roving or all the time?

 

nipper

 

 

Seems like every time i'm stopped and in gear.

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