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06 with multiple error codes the dreaded "mis-fires"

4K views 22 replies 7 participants last post by  Subie Doo 
#1 ·
Hi folks,
I have been dealing with CEL problems for almost a YEAR! And I'm getting tired of it! :mad:
The car is an 06, manual.

I've read the post "Engine mis-fires? Read This First!" and most of the things on the list have been done, except actually pulling the engine, removing the heads and looking at the valves and guides. (I REALLY don't wanna go THERE) :eek:

My neighbor has a scan-tool, so we were able to pull the codes, and here is what we got:
P301 Cyl 1 misfire
P304 Cyl 4 misfire
P1153 O2 sensor range high
P0131 O2 circuit low voltage bank1 sensor 1

The car seems to drive ok, although I do notice a little stumble once in a while at idle.
The air box has been replaced because I used to use a K&N and it broke the lid tabs which freaked out the MAF sensor. And the MAF has either been cleaned or replaced, I don't remember which right now. Have also used BG Chemtool with some success. (My shop tells me to run nothing but Chevron. No cheap stuff.)

The shop I go to specializes in foreign cars, mostly BMW, Audi, and Porches, but they also service a lot of Subarus, so they have experience with the cars, but I'm thinking about taking it to a Subaru dealer shop, because they just haven't seemed to get rid of the problem for good. Despite the fact that I trust the guys at my local shop.

The cyl mis-fires appear on all cyls. That is, I have seen them show up on all cyls, just not all at once. This time, it's 1 and 4, last time it was 3.

Could there be something wrong with the O2 monitoring system that could cause the misfire issues, considering that I'm getting those error codes too?
 
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#2 ·
I can't speak for a Subaru, but I have heard of O2 sensors causing random/multiple misfires in other vehicles, and in a single isolated case, a consistent single cylinder miss. So it is possible. If you haven't already, I'd suggest double-checking your vacuum lines. I had all four cylinders throw miss codes, until I undid whatever the previous owner had done with the vacuum lines (I believe he had an external wastegate that he took off when he traded it in). Car ran like total crap, but it purrs now.
 
#3 ·
You said you did "most" of the things in the misfire sticky, could you give us a list?
 
#4 ·
1. Wrong, worn or incorrect gapped spark plugs. You should run only NGK stock range plugs gapped to .028. DID THIS

2. Clogged injectors/dirty fuel filter. Try changing the fuel filter. The maintenance schedule is every 30K miles. Have the injectors cleaned or at least run several bottles of a good injector cleaner through the engine. Also make sure you are using the correct octane gas! Either 91 or 93 unless you are specifically tuned for another octane!! (IE: race gas or E85). RAN CLEANER THRU SEVERAL TIMES. WHERE IS THE FUEL FILTER?? IS IT IN-LINE OR IN THE TANK?

3. Check valve clearances & compression. Leakdown/compression test. DONE

4. Oil or dirt build up on MAF sensor. This causes an incorrect load reading which make for AFR corrections out of line. Misfires can result. Remove the sensor, place in plastic bag. Spray out with CRC MAF cleaner or NON chlorinated brake cleaner. CLEANED OR REPLACED

5. Vacuum leaks or preturbo leak. Check where the FPR hose connects (generally you could get a P0457 or P0171 with this as well). Check the turbo inlet pipe where it connects to the turbo. This pipe is famous for ripping and causing a huge preturbo leak (P0171 as well). NOT DONE, BUT DIDN'T GET ANY OF THESE OTHER CODES

6. Clean the battery ground cable and ones that run to the intake manifold. These are sensor grounds and must be kept clean. Clean coil pack grounds (bolt holes). I BELIEVE THIS WAS DONE

7. Cam timing. Check cam timing per the service manual. Clean cam sensor face. NOT DONE

8. Excessive PCV blow by. PVC gases will effectively lower the octane content of gasoline/petrol. NOT CHECKED, HOW IS THIS DONE?

9. Carbon build up on motor. Real common on EJ205's. Get some BG Chemtool, GM top end cleaner or other type of carbon remover. GM top end cleaner seems to work really well. HAVE RUN SEVERAL CANS OVER A PERIOD OF MONTHS

10. Lightweight flywheels or crank pulleys. (phantom misfires) Clean crank sensor face. DON'T HAVE THESE

11. Bad/loose coil pack or coil pack connector. Test coil pack and move to other cylinder to see if DTC changes. Also check the tower boot for corrosion. ALL NEW COIL PACKS INSTALLED

Misfires all cylinders: Coil pack connectors mixed up (black to back),light weight flywheel,bad/unplugged crank or cam sensor,incorrect gapped plugs,cam timing off ????????

Thanks for the input, guys!
 
#5 ·
Anyone tell me where the fuel filter is? Is there more than one?

Also, anyone know if the Shingle Springs Subaru dealership has good, trustworthy mechanics? I tend to distrust dealerships and is why I choose good independent shops. But my guys haven't been able to nail it, and is why I'm considering taking it to Subaru.
 
#6 ·
In an 06 it is in the tank. Technically not servicable, but you can buy it from Subaru and replace it.

In that case, I'd probably go ahead and replace the pump while you're there if you have the funds.
 
#8 ·
Well, I hope I've gotten to the bottom of this problem after all this time....

On advice from one of the kind folks here, I decided to take it to FW Motorsports in Rocklin, not far from where I live. Since the guy is a certified Subaru mechanic and pretty much all he does is Subarus (and he's not a dealer) and he was given good recommendation, if he couldn't find the problem, well....

He did. Found a couple actually. Front O2 sensor and an air/fuel sensor was the first things he pulled codes for. He'd noted the car "was not running happy". Replaced the sensors, hoping that would take care of it, without having to get into the top of the motor. Well, I'm pretty lucky, but not that lucky this time.

He had told me ahead of time that the '06 2.5L Turbo engines in the WRXs, not the Legacys nor the Outbacks, had issues with the valves sticking, or more accurately, the valve "buckets" that the cam lobe rides on. You find 'em by measuring the clearance between the cam and the bucket. If the result is outside a certain range, the bucket/valve is sticking and causing a mis-fire. If that's the case, the buckets are replaced and re-checked.

So after fixing the sensors and driving it around a while, he finally pulled a misfire code. I guess I had cleared the previous misfire codes with my neighbor's scan-tool. At that point it was pretty clear, I wasn't going to be lucky today, and the valve bucket job was going to have to be the solution. A $1200-1500 job. (The sensors had cost just shy of $400 installed)

I get the car back in a couple days (weekends, sheesh!) so I'm looking forward to driving w/o a flashing light in my face.

Oh, and props to my local garage Hangtown Foreign Car Svc for trying so hard on this, and, actually arriving at the same conclusion about the same time as FW Motorsports did. Those guys are no slouches. But FW Motorsports new right where to go right off the bat. Experience with the brand. Nothing beats it.
 
#9 ·
Two days after getting the car back from FW Motorsports and the car is running great again! YAY!! :woocow:

Not only is the car running like it should again, the engine bay was cleaned too! BONUS!

Now let's see what my gas mileage does....should go back up.

I was really impressed with FW Motorsports in Rocklin. Paul knows his stuff, is very friendly, explains stuff to ya, and he keeps you posted on the progress, either by phone, email, or both. I got out of there for under $1250, which I consider a good deal, considering:
Air/Fuel Ratio Sensor replaced (Part cost $200)
Oxygen Sensor replaced ($127)
Two new Valve Cover Gaskets
Four Cam Plugs
Four Cam Seals
Four Valve Lifters (Buckets)
and an Oil Change!
Plus all the labor.....

So, if you have a 2006 WRX and you're getting bad mileage, a check engine light, and mis-fire codes, get your valve clearances measured. Chances are, you've got sticky lifters.
 
#11 ·
Confused as to why a compression test didn't indicate Valve issues? Do you remember what your compression numbers were, I am having similar issues, no CEL's but not making power like I should. Car doesn't smoke, so I'm really hoping its just a valve adjustment and buckets vs a ringland and or piston issue. Anybody else have experience with this? I'm down about 50hp. Check the spark plugs they are good... but that is really all i have done so far, hopefully with compression check tomorrow.
 
#12 ·
Yeah, I don't know why a leak-down test didn't find it. But maybe I don't understand how a leak-down test works. Maybe it's only supposed to find bad valves or rings? But the way he determines how a lifter is bad is by taking off the valve cover and measuring the clearance between the cam and the lifter. if it is outside a certain range, it means the lifter is sticking and it has to be replaced.
 
#16 ·
You had misfires on all cylinders and the diagnosis was the valve lifters? :confused1

Something sounds fishy.

Beamed at your face at approx. 186,000 miles per second via DROID BIONIC
 
#17 ·
Not really. The valve lifters (or "buckets") that cover the valve stem/spring/retainer ride in a depression in the cylinder head, sort of like a piston. If a lifter sticks, it will not allow the valve to close all the way, leading to a misfire. They don't stick every time, just once in a while. It's possible to have sticky lifters on multiple valves, consequently I saw misfires on every cylinder. He replaced four out of eight lifters. The car now runs like it should. Makes perfect sense.
 
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