Subaru, Multiple Misfires

Brad Manager California Posted   Latest   Edited  
Unsolved
Driveability
2002 Subaru Impreza WRX 2.0L (EJ205) 5-spd (TY754)

We're a Porsche shop working on an employee's Subaru. The check engine light comes on randomly, and the codes are misfires on usually 3 out of four cylinders, but not always the same 3 cylinders. The engine always seems to run smoothly, regardless of the misfire codes / check engine light. The issue usually arises while warming up, and decelerating, but sometimes it won't occur for several hundred miles. Is there a known common problem here? So far we replaced spark plugs, ignition coils, hot soak sea foam cleaning, 44k in the fuel on several occasions. The car has about 145k miles. Not sure about the valve adjustment history.

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Saifullah Diagnostician
Ontario
Saifullah Default
   

No timing codes? Vvt oil control valves checked out? Fuel trim numbers? Fuel pressure?

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Eric Mechanic
North Carolina
Eric Default
 

Any FF data?

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Doug Owner
Michigan
Doug Default
 

We are refining a technology that uses the First Look Sensor (FLS), placing one in the oil dipstick tube and one in the exhaust to assist with diagnosing issues just like the one you describe. Because there may be a variety of factors at work, it helps to know what the conditions are and how much "dirt" is building up. You can get an idea of what we are looking for by just placing a FLS in the…

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Wayd Owner/Technician
Montana
Wayd Default
 

I would recommend inspecting the valve lash. Tight valves are a fairly common cause of misfires on these engines, often with few or no other symptoms than a CEL, until the valves actually burn. I have not found a way to nail it down without physically checking clearance. The reply from Doug about using the First Look Sensors to nail this type of thing down is very intriguing to me. As a small…

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Steve Technical Support Specialist
Connecticut
Steve Default
 

I would second the tight valves. They never get adjusted and the exhaust valves receded in the heads dropping the clearance. Usually by the time the misfire codes start setting the valves are already damaged. We see it on all the early turbos both 2.0 and 2.5. You can almost always set a misfire code after a 5-10 minute hot soak on restart. Initially it's random then gets more consistent on…

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Nathaniel Diagnostician
Ontario
Nathaniel Default
 

Agreed, a pressure transducer tapped into the exhaust somewhere upstream of the turbo should show exhaust valve problems. Ditto for intake, just easier to check. If a pressure transducer for your scope isn't in your kit yet, a good quality vacuum/pressure gauge will suffice. That said, at 145k, going straight to checking valve clearance is probably not going to waste your time.

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Russell Technician
Idaho
Russell Default
 

Drop exhaust pipes from cylinder heads and see if valve guides have dropped

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Jason Technician
New Jersey
Jason Default
 

Hey what's up Brad. When u mentioned on deceleration first thing that comes to mind is and egr issue. See if u can graph the egr command pid if equipped with upstream and downstream 02 sensors to see if it happens after the egr command.

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Hollis Technician
Colorado
Hollis Default
 

Start with checking valve clearances. You can remove the engine mount nuts and ease the engine over side to side for a little more working room. All stock intake and exhaust components ? Any aftermarket add-ons? Any Tuner-Stuff done ? What are you using for a scanner? If your scanner has a misfire counter in enhanced data, have a look... Misfire while warming up and on decel, Hmmm??? Some…

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Duane Owner/Technician
West Virginia
Duane Default
 

There are several updates for Subarus to fix misfires codes by reflashing the PCM. If you already have a j box there software is only 90 bucks for a full year. Duane

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Andy Owner/Technician
Oregon
Andy Default
 

The early run wrxs has a reflash for ghost missfire codes I would start here next check fuel pressure when it acts up the wrx did weird stuff managing fuel pump and I’ve seen a number of them with intermittent fuel pressure loss causing misfires.

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Hollis Technician
Colorado
Hollis Default
 

You made me look. I checked my latest Re-Flash version not there, it's on earlier versions. I guess they omit earlier models, can't blame them.

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Brad Manager
California
Brad Default
 

Thank you, Duane. Could you tell me where to get this software? Is it a download, or cd-rom?

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Duane Owner/Technician
West Virginia
Duane Default
 

It is actually a CD ROM. You will need to order it from Subaru. Go to the Subaru website and click the drop down arrow next to the information tab. From there click on the Special Tool Information. Then just scroll down to the J2534 section for more information. Here is the phone number to order the CD … The CD is $75.00 plus shipping. If you want it quickly it will cost about…

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Brad Manager
California
Brad Default
 

Huge help, Duane. Thank you immensely.

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Hollis Technician
Colorado
Hollis Default
 

Make sure you tell them what year model you're working on. Calibration look up is … and 2004 and later. I looked on our current reflash for your year model and the misfire reflash wasn't there. Luckily I still had an older version on an older laptop and it was listed. Are there any local Subaru specialty shops in your area? Or even a dealership, might be cheaper and…

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Benjamin Owner/Technician
Georgia
Benjamin Default
 

Coolant could be pooling on top of pistons and burning off when engine cold. I agree that I would start with checking for current pcm software versio, then valve lash As others stated.

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Eric Technician
North Carolina
Eric Default
   

Does this car have a lightened flywheel or crank pulley? No egr or on an 02 wrx.

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Rudy Technician
California
Rudy Default
 

Id be looking for coolant in the cylinders.

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