SOLVED: Very rough idle, diagnostic code P0018

I have a built MY2010 EJ257 engine in my 08 STi, Edwin's old engine.

I was on "E" today, filled it up at my usual spot and it took 14.3 gallons. Started fine at the pump, drove about one and a half miles home and while in the garage I noticed a very rough idle, the whole car was shaking. I initially thought it was bad gas, but I threw a P0018 (CRANKSHAFT POSITION - CAMSHAFT POSITION CORRELATION (BANK2)).

I did some searching, which lead me to replace the crank shaft sensor with one from my stock engine. I was getting actually ready to replace the cam-shaft sensors as well, but I don't have the tiny hands, dexterity or proper tools to get to those without removing the intake manifold. So I reset the code using the AP and fired it up, still idled like absolute garbage. I shut it down and fired it up again because the service manual says "Detected when two consecutive driving cycles with fault occur," and sure enough the P0018 came back.

Right now the path I'm taking is with the driver side AVCS. I'm going to see if I can take the one off of my spare (stock 08) engine and put it on to see if it helps clear things up. From what I understand an oil passage might be blocked or clogged preventing the AVCS from adjusting timing properly.

This kind of makes sense, because when I monitor sensors with my Cobb Accessport the values on the AVCS sensors are radically different from eachother. They show in degrees, one is 65, and the other is 5.

I wish there was a way to check timing without removing all the damn belts and covers. >.<

It's weird though... I barely ever beat on the car, and today was no different. I was in "I" mode all day, put about 50-75 miles on it and it was fine until I got home into my garage. It was fine in the morning, it was fine when I started it up and let it come up to temp when I left the office, it seemed fine when I started it up after getting gas. Then I get home and I'm just about to turn it off when I notice the shaking.

I called the gas station where I filled up to let them know of the issue, in case they needed to file some sort of incident report just in case. The lackey that answered the phone didn't really give a damn. Which is what I expected, but I still wanted to call them so I can say I did.

I had this exact same problem. Every single symptom was the same. I ended up replacing my cam shaft pos sensors 3 times and too no avail it kept poping back up. You might want to check the wiring too those sensors and also the main bundle from that head. Mine tuned out be to be frayed wiring causing intermittent connections. Just something too think about, there are three different cam shaft positions sensors for that engine, make sure you have the right one in the right position, as that could cause problems. Finnally I would say last thing would be too check the bango bolts/oil galleys too that head and see if any are clogged, I doubt it but who knows.

Vermont said:

I had this exact same problem. Every single symptom was the same. I ended up replacing my cam shaft pos sensors 3 times and too no avail it kept poping back up. You might want to check the wiring too those sensors and also the main bundle from that head. Mine tuned out be to be frayed wiring causing intermittent connections. Just something too think about, there are three different cam shaft positions sensors for that engine, make sure you have the right one in the right position, as that could cause problems. Finnally I would say last thing would be too check the bango bolts/oil galleys too that head and see if any are clogged, I doubt it but who knows.

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Thanks, these are on my list to check tonight... going to be a long night.

Fujiwara said:

Which one is the cam that advances crazy?

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I don't remember if the AP reported it was "left" or "right" that was at 65, if that's what you mean... I'll check tonight to be sure. The diag code (P0018) refers to correlation between the crank shaft sensor and the cam shaft sensor on bank 2 (driver side).

Tonight I'm going to be rechecking the harnesses going to do the following;

• Check harnesses going to cam shaft sensors.
• Replace cam shaft sensors.
• Check AVCS solenoids and lines for blockage, maybe replace these as well.

Is it OK to drive the car 2 miles to the shop to have access to better tools? Or is that all sorts of a bad idea? The car goes into limp mode, so if I stay out of boost, am I safe?

What I've done so far;

• Check harnesses going to cam shaft sensors.
• Replace cam shaft sensors.
• Check timing marks on all cam gears.

The harnesses were fine, and I didn't jump a tooth anywhere. Cam shaft sensors were replaced from my 08 STi engine, so that makes all three sensors (crank shaft sensor and both cam gears) replaced. I fired it up the first time and it actually seemed like I had it taken care of... I let it idle for a few, then turned it off and back on... shook like crazy, back to crap idle. Sure enough P0018 is back. Seems logical that something might be floating around in the driver side (left, bank 2) AVCS solenoid or line and that it had time to settle elsewhere since it sat overnight. Then after the oil got flowing today, it worked its way back into the mix... going to remove those next and take a peak.

Oh, on the Cobb AP, AVCS Left is the one with crazy numbers. It is showing 50 degrees at idle, where the AVCS Right is showing 0-5.

Next up;

• Check AVCS solenoids and lines for blockage, maybe replace these as well.

When I was going through this issue a shop near me reported that some times the bango bolts leading too the AVCS solenoid have a filter in them, if this filter becomes clogged, then it can cause this problem.

As far as driving the car you will be fine just make sure and stay in CL and out of boost. Shit me and holy tuned my cars closed loop with this very same issue, although it was acting up less severely at that time.

Fujiwara said:

Avcs near the merge collector was the solenoid and casting that I replaced with a brand new solenoid, casting and gasket. It would be the left side of the motor as you see it looking into the engine bay. Unless Subaru messed up the casting itself, I don't think the part itself would be the issue. If all else fails, maybe take off both castings, clean them out, clean out the solenoids and make sure they look like they should according to the service manual.

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By the casting, you mean the solenoid that slides into the casing on the engine block? These are going to be a bear to get to with the breather lines on, that's for sure... and there's so much stuff in the way of even getting to those. I'll start dismantling.

Vermont said:

When I was going through this issue a shop near me reported that some times the bango bolts leading too the AVCS solenoid have a filter in them, if this filter becomes clogged, then it can cause this problem.

As far as driving the car you will be fine just make sure and stay in CL and out of boost. Shit me and holy tuned my cars closed loop with this very same issue, although it was acting up less severely at that time.

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I removed the banjo bolts from both AVCS feed lines (where it says "Engine Oil Pressure") and there were no screens in there at all. I also checked this on my 08 STi engine and they were present their either. I couldn't see any obstructions while looking down the hole where the banjo bolt went.

I suppose I'm going to remove the part labeled as "Oil Control Valve" which has the cylindrical gears attached to it and see if there's anything clogged in there.

OK, I pulled things apart and got the driver side AVCS solenoid off... I can't see anything clogged in there, Hopefully I can get to that plate on the side of the casing that the solenoid goes into, see if anything is wedged in there.

I was curious so I pulled my driver side AVCS solenoid out of my 08 STi engine and found that it was quite different. The one from the 2010 engine (Edwin's old built engine) is shorter and has one more 'port' on the bottom, where the one from my 08 STi is longer and a bit bulkier.... additionally the 08 seems to have a restrictor (?) on the end, maybe?

I slid the 08 one in the 2010 engine (Edwin's old built engine) and it fit all the way in, would it be OK to use the 08 to see if this helps clear things up?

Re: Very rough idle, diagnostic code P0018

You said you replaced the left solenoid and casting as you looked into the engine bay... wouldn't that be the passenger side? The solenoids I have pictured are the driver side solenoids from the two different model year engines.

In that note, both solenoids and castings from the 08 engine were identical, as were the two from the 10 engine.

Re: Very rough idle, diagnostic code P0018

Then this raises a flag... my stock 08 STi engine has identical AVCS castings and solenoids in both sides. They're different from the 10, as seen in the pic, but they're definitely identical. Interchangeable even.

The intake don't have sides, the exhaust don't have sides, however they are different. The exhaust housing is different, and the intake housing is different. If you have two of the same intake or exhaust housing you have either two right or two left heads on that car. The intake housing is not sold alone you get it with the heads.

My point is you can't just buy the housing. it comes with the head. I am looking right at the parts diagram, it is a non servicable Item meaning it comes with the bare heads.

You got them used. Not new, plain and simple, I sell parts for a living, there is no way to buy new from a Subaru dealer or from SOA, was my picture of a 257 parts diagram not clear enough to show that there is no part number for that piece therefore not available!

You are taking single avcs he is talking about dual avcs head. They are not the same. You can get the housing for a single avcs no problem

I have even called SOA to ask them about it. They tell me that it is an unavailable part. What is the part number you purchased so I can look deeper into this.

I'm trying to be as clear as possible for these posts. If anyone needs clarification, feel free to ask.

From here on out, I'm considering the following terms synonymous, and will refer to them as OCV's.

• Oil Control Valve (OCV)
• AVCS Solenoid

Edwin, as you suggested, I tried feeling around in the passenger side cylinder where the intake cam OCV goes. Which is the one you said you replaced. I couldn't fit my big ass fingers in there, so I took a picture. The holes inside the cylinder line up with the OCV that I pulled from my 08 STi, the longer ones, not the shorter ones that were in the engine as it came from you. There are four (4) holes on the top and two (2) on the bottom.









As stated previously...
Both of the intake cam OCVs from the the MY2010 STi engine (your old engine) were identical, they're the shorter ones in the picture.
Both of the intake cam OCVs from my old MY2008 STi engine were identical, they're the longer ones in the picture.

For good measure, I also took out the driver side exhaust cam OCV from my MY2008 STi engine and it appeared to be identical to the intake OCVs from the MY2008 STi engine.

Right now I'm drawing the conclusion that the intake cam OCVs that were in the MY2010 STi engine weren't the correct part numbers. I am going to try to get to the Subaru dealer to speak to a technician tomorrow if time permits.

If the problem is the wrong part in the engine, I'll be infinitely perplexed about how this issue showed up out of nowhere after putting a full tank of gas in. It will be one of the biggest coincidences of my car modifying 'career'. On top of that, how the hell has it been running so well for the past few weeks... CONFUSED.

Did some searching...

Part number 6 in this diagram from OpposedForces.com is called "Valve assembly-oil control" and has a part number of 10921AA080.



If you search that part number on the internet... you get nothing but pictures and links to the OCV that I have in my 08 STi engine.

Re: Very rough idle, diagnostic code P0018

Exhaust cam advance? My problem is intake cam advance, right? So it makes sense to me. The part number I found was for the intake OCV.

Also having the seemingly wrong intake cam OCVs doesn't raise any flags?

Fujiwara said:

If the solenoids are different lengths with different piling holes and you decide to replace the solenoid with one of those older ones from your motor, I'm betting it isn't going to work at all.

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My problem with this statement is that the holes on the OCVs from my MY2008 STi engine line up exactly with the holes in the intake AVCS cylinder (top of head) on the MY2010 engine... The holes on the OCVs from the MY2010 STi do not, which leads me to believe the ones that are/were in there weren't correct in the first place. Actually, if you look at the pics you'll see that the holes on the MY2008 STi OCV also line up exactly with the holes on the MY2010 STI OCV. The only differences are the length, which I stated previously that both MY OCVs fit in the AVCS cylinder fine... and that one hole is relocated from the bottom of the MY2010 STi OCV to the top of the MY2008 STI OCV.

Here is another picture for further clarification.

Fujiwara said:

Since I clearly did not understand the issue, you need to do some very basic troubleshooting of the wiring harness first thing. Then you should test each solenoid for functionality and resistance. Solenoids do go out.

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I have visually checked, double checked and triple checked the sensor wires. I will hook a multimeter up to each sensor wire with the ignition in the ON position (but not cranked obviously) and see what they read. As for testing the solenoid, how can I test to see if it actuates properly?

Fujiwara said:

To test the solenoid, try to actuate it with the appropriate signal. In this case it is probably PWM.

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What is PWM?

Fujiwara said:

However, if you've checked everything except for the solenoid in that system, the are only a few possible culprits: actual cam timing of that particular cam, the cam position sensor or the solenoid itself. I would check both considering that the timing belt was pulled off that motor.

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I can only answer this with this...

Deek said:

What I've done so far;

• Check harnesses going to cam shaft sensors.
• Replace cam shaft sensors.
• Check timing marks on all cam gears.

The harnesses were fine, and I didn't jump a tooth anywhere. Cam shaft sensors were replaced from my 08 STi engine, so that makes all three sensors (crank shaft sensor and both cam gears) replaced.

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At this point, it seems that the issue is either something floating around in there making its way to the oil passage line from the block to the OCV, or the OCV itself is defective.

I'm going to try to stop by Subaru on lunch to verify which OCV(s) belong in that engine. If it turns out that the MY2008 STi OCV(s) are the correct ones, I'll put them in and update.