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Misfire in 1 & 3


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So I got my engine rebuilt and in the car. It runs great aside from these two misfire codes (P0301 and P0303). The codes don't show up until the car idles for a few min. I can drive 20 miles and not get any codes but as soon as I come to a stop and et it idle the codes pop up. Here's what I've done so far.

 

New Coil

New Wires

New Plugs

Compression check (160-175psi accross the board)

swapped injectors with 2/4

new timing belt, pullies, tensioner

No vacuum leaks

new PCV valve

Adjusted throttle position sensor to correct voltage

 

This was all done during the rebuild. I'm not sure what else could cause this issue. I'm going to start looking into the fuel system tomorrow, but I'm doubtful. I could really use soem help with this. Thanks

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It has a rough but constant idle. Doesn't try to stall or anything. Acceleration is great. No hesitation, no missing, just a nice even pull. I had the ECU out the other night when I was checking the TPS circuit. It was clean and dry no corrosion and the connector fit snugly. I'll check the mass air circuit tonight.
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Check the iACV?

 

Yes I've swapped both that and the EGR valve with ones on the other manifold I have. I cleaned them both before putting them on. Also I would think the IACV would effect all cylinders wouldn't it?

 

One of the guys I worked worked with suggested adjusting the valves. I'd rather not have to do that though.

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So last night i did an induction service. At first I thought it fixed it. Car idled smoothly for about an hour with no CEL. Took it out for a drive for about 10 min and when I stopped to idle CEL started to flash. I'm pulling my hair out here. Any other ideas?
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live data FTW! record and get it to misfire. Hopefully the new scan tool has bank 1 and 2 fuel trims. That'll really tell you what's going on when you go WOT, and you can determine if it's spark or fuel. Or, it could possibly be a valve not opening all the way.
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Last night I swapped EGR Valves and IACV. Also replaced every vacuum line on the engine. I also did a leak down test and found that 1 and 3 are not closing valves fully. I got 35% leak down in cylinder 1 and over 50% in cylinder 3.

 

So now the question is, is it Valves out of adjustment or is it valves sticking?

 

Also got some more FF Data

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if the valves are not holding pressure, closing fully, then they are either bent or burned, is my guess. i vote foe bent but you will not know until you open it up. and you have to open it up to fix either problem.

 

the belt probably jumped time and bent valves. you might try and replace the belt and re-time it and do the test again just to see what you get. i don't really know if it could improve. if bent there is no way it will improve. but i'm not familiar with how a leak down test is done so i'm not clear if correct timing will improve your situation.

 

when you remove the timing covers, if the timing is off, and i think it will be, i would redo it and re-test it . especially if you are planning on repairing the engine. any parts you buy will still be used after the repair. knowing what's wrong before you pull the heads is a plus.

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All the timing components are brand new. I pulled the cover off the passenger side and both pullies lined up with the double hashes and the hashes in the cover. I'm going to see if I can borrow the special tool from our subaru dealer to do the valve adjustment in the car.
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Yes the cams were out during the rebuild, but I didn't mix up the buckets. When I cleaned the heads I left all the buckets on the tool box in order. I got some quotes from a machine shop on rebuilding the spare heads I have and a PnP for about $500 so I'll probably go that route.
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you can check the valve clearance with the heads on and engine it the car. do that first.

 

intake valves clearance loosens over time and exhaust tighten. at least then you will know how many need adjustment or replacement. once adjusted properly drive it and see how it does.

 

the gas leak test will tell you if they need to be replaced. once the heads are off you can test the valves to see if they are sealing by pouring gas in the ports, intake and exhaust. the gas should not leak out through the valves. this will tell you which are not sealing. they will need to be replaced?

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  • 3 weeks later...
So After 2 weeks at IAG Performance the car is fixed. Dropped it off on the 27th of dec. Called me same day to inform me they needed to special order the valve adjustment tool and since Subaru was closed Friday the 30th and Mon the 2nd the tool didn't com in till last friday. Valve adjustment done along with another new set of valve cover gaskets, spark plugs, and shims. I was told it still has a slight miss but it's not throwing CEL.
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