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Help- Valve adjustment advice on a 1999 EJ25 DOHC

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My car has a progressively worse miss on cylinder 4. I've done the typical stuff, plugs, wires, coil, cam position sensor, crank position sensor, fuel filter, clean EGR, etc.

 

No improvement- problem is getting worse with milage. Miss mainly occurs at idle, seems to clear up at higher rpm.

 

I took the car to a "subaru specialist" private mechanic, because I suspected the valves were out of adjustment.

 

Mechanic tells me compression in cylinder 4 is off by 15 lbs (similar results to my test), and that it is a valve issue.

 

However, he is saying the do not normally need adjustment and he needs to pull the head and replace the valve.

 

My understanding is that they are adjustable, and subaru has a 100,000 mile service interval to check these?

 

After questioning this, mechanic tells me even if they are adjustable, he needs to tear down the head to reach them and at that point he might as well take the head off to replace the valve.

 

What is your opinion here?

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The valves are adjustable. There is a shim over the bucket that you replace with a thinner or thicker one to change the valve clearance. Unless you have the special tool from subaru, you have to take the cams out to change the shims. You can take the cams with the engine in the car. In fact, you have to take the cams out first to pull the head off.

 

What happens sometimes is that as the valve wears into the seat, the valve clearance gets too tight and the valve hangs slightly open and you end up with low compression. You would check the valve clearance to see if this is the case. If it's tight, then this is likely. The proper way to fix this is indeed to pull the heads, do a valve job and reshim all the buckets. A cheap and easy way out that usually works is to just reshim the tight valves.

 

If the valve clearance isn't too tight it may have a valve that is burned or not seating.

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Thanks. After further talking with the mechanic, it comes out that he does not have the tool, and was balking at adjusting the valves, because labor for him without the tool would be similar to pulling the heads.

 

We also dicussed that the valve could possibly be damaged and or burnt. The fact that the misfire has become so prevalent in such a quick period of time could mean this.

 

The course of action is he will check clearance, and we will go from there.

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I have no idea what type of tool this special tool is, but it would have to be something really special. The adjustment button sits on top of the valve stem, under the cam follower (which looks like a shot glass turned upside down and placed over the valve assembly). Since you would have to remove the cam follower to replace the button, I don't see how any tool could do this without removing the cam. Usually the only time you would make and adjustment is after a valve job. It sounds like either your valve stem is stretching or the valve seat is wearing out, either one would require a valve job.

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I have no idea what type of tool this special tool is, but it would have to be something really special. The adjustment button sits on top of the valve stem, under the cam follower (which looks like a shot glass turned upside down and placed over the valve assembly). Since you would have to remove the cam follower to replace the button, I don't see how any tool could do this without removing the cam. Usually the only time you would make and adjustment is after a valve job. It sounds like either your valve stem is stretching or the valve seat is wearing out, either one would require a valve job.

 

The EJ25 phase 1 dohc has the shims on top of the buckets. The tool pushes the bucket down and lets you take the shim out without removing the cam. The are 2 notches in the bucket that the tool sits in.

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From what I understand, you need the special tool to remove/replace the shims with the engine in the car due to space issues. If the engine is out on a stand, there is plenty of room to do the job with scredrivers and other implements. I haven't done it on an EJ25D, so I don't know for sure.

 

My previously owned Volvos and one VW had the same bucket and shim arrangement, but with the head right up there in the open, there was plenty of space to use screwdrivers, etc, to change out the shims.

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There is a special valve adjusting tool which compresses the springs. There is a notch in the bucket which holds each shim in. When the spring is compressed there is enough clearance to prop out of shim out of the bucket.

Of course there is a detailed procedure in the Haynes manual on how to 1st measure each valve clearance. It is too lengthy to post here.

 

If your doing this you might want to think about checking the cam seals at the same time. I have a mid year 98 and am just getting done with replacing HG's & most of all the engines seals, gaskets,ect.. I am the orig. owner and found that on those cam seals they were just starting to leak at 107k miles. The factory used a black rubber type seal (either buna or neoprene). The new replacement OEM seals are viton which last significantly longer(just a thought). Shouldn't be too difficult, except for stooping over for access. If you PM me, I can either scan & e-mail or fax you the procedure.

 

Good luck.

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There is a special valve adjusting tool which compresses the springs. There is a notch in the bucket which holds each shim in. When the spring is compressed there is enough clearance to prop out of shim out of the bucket.

Of course there is a detailed procedure in the Haynes manual on how to 1st measure each valve clearance. It is too lengthy to post here.

 

If your doing this you might want to think about checking the cam seals at the same time. I have a mid year 98 and am just getting done with replacing HG's & most of all the engines seals, gaskets,ect.. I am the orig. owner and found that on those cam seals they were just starting to leak at 107k miles. The factory used a black rubber type seal (either buna or neoprene). The new replacement OEM seals are viton which last significantly longer(just a thought). Shouldn't be too difficult, except for stooping over for access. If you PM me, I can either scan & e-mail or fax you the procedure.

 

Good luck.

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I would also look for vaccum leaks that might be plumbed in that cylinder too. can cause the same symptoms. Compression reading could be lower on that cylinder due to fuel washing the cylinder (from the miss) Could also be a crappy spray pattern from an injector. (also a "miss at idle" conspirator)

Is it any better while the engine is cold or hot?

Not saying its not a valve problem, Just throwing other things out there.

Edited by rub2race

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