Seattle Area Subaru Burnt Exhaust Valve
A fairly common repair we have had to make to the 2004 and up Turbo charged 2.5l is a valve job as a result of one or more burnt valves, but what is a burnt valve and more importantly how can I avoid it?
Subaru Exhaust Valve Issue in Seattle
Subaru Exhaust Valve Problem
Seattle Subaru Burnt Exhaust Valve
Typically what causes a valve to become burnt, worn or cracked is excessive heat either do to lack of lubrication or excessive combustion chamber temperature as a result of the incorrect fuel mixture. A weak fuel injector is typically the culprit on an DOHC Turbo charged models from 2004 to 2008. This usually starts out as some rough running when cold and finally setting a check engine light with a cylinder misfire code. If the weak fuel injector is not caught it can slowly overtime allow the combustion chamber temperatures to become higher than designed ultimately damaging a valve. There are of course other reasons this can happen such as tolerances that are not within specs, or a driver that constantly pushes the oil change intervals a little to far. Its also possible that the valve it self is defective we have seen that as well. What we have noticed is that based on the misfire data observed form these engines when cold there can be some minor signs of trouble long before the check engine light is ever illuminated, we whenever possible for our local Subaru customers in the Greater Seattle area will connect the Subaru Select monitor to the Turbo models and try to look at some data from history if we don’t get an opportunity to have the vehicle cold.
If you own one of these vehicles and if you start to notice a vibration from the engine when cold at idle I would encourage you to have the misfire data monitored especially if you have a vehicle that is still under Subaru’s 5 year 60,000 mile power train warranty as making the attempt to complain about it ahead of the warranty expiring may extend the warranty for you a bit . We typically suggest a fuel injection service starting at the 60k interval as maintenance and I can tell you we that when we have observed a weak injector there really hasn’t been to much we have been able to do short of replacing the fuel injector it self.
I wan to stress that its after we have seen the same type of issue multiple times and think we have a theory on whats happening and can provide some information that should help Subaru Owners avoid an expensive repair that I will finally post the article. If its a one time thing there is almost never going to be a post about it, but after 6 or 7 repairs a theme is starting and I believe it time to get some information out to our readers.
Thanks for reading
Justin
Justin –
I recently bought a 2005 LGT 5MT and have been trying to fix a rough idle (no roughness when I’m driving). So far I’ve replaced the plugs and used various fuel injector cleaners from the parts stores. Neither seemed to work. No CEL either. My two questions:
Based on what customers have told you, how long is the timeframe between a rough idle and a CEL appearing?
Also, will an OBD scanner show trouble codes even if the CEL is off?
Hi Matt,
I would start by connecting a vacuum gauge when cold and look for unstable vacuum reading, perform an injector balance test, then remove the valve covers and check the valve clearance in order to diagnose the issue.
I would perform all of these tests cold.
Its tough to put a time line to it as everyones perception is so different, sometimes we point out issues that customers are completely unaware of and other times the driver is so in tune to every noise, shimmy and shake they will become hyper critical of there car as it ages.
Hope that helps
Justin
I have a 05 legacy gt with 55k miles. misfire in cylinder 2, P0302 and P0000. changed injector and swapped injector, swapped coil packs, new plugs (oem). Dealer claimes the valves have zero clearance. Another shop did a leakdown test and everything looked good.
thoughts?
car runs fine, the idle is not the best, but which subaru is?
Actually modern Subaru’s idle just as smooth as any other car out there. If the valves clearance is out of spec than most likely one or more of the sodium filled Exhaust valves has burnt. Which causes the stem to become closer to the mechanical lash adjuster and then the cam shaft.
It will continue to get worse, and if not repaired the valve can and will chip and break apart resulting in catastrophic engine failure that will result in a potential huge Expense (we have seen it happen), the cost can be controlled now if you repair it, but if you drive it until the valve fails and it destroys the engine you can be north of 8k in expense where you should be under 3k now.
Further more I would ask when did the problem first show? Was it under the 5 year 60k power train warranty?
one more thing, the cel came on about 1 month ago. for the last few days, the car wont fire up right away, it will crank fine just not fire up. this never happened before the cel.
[...] Take a look at this article from Subaru Repair Seattle. They belive the burnt valve is a result of a failing fuel injector. Very common I guess on the 04+ turbo motors. These guys are extremely knowledgeable, and I would suggest emailing them with your problem and asking them for an estimate of what you should expect to pay to repair this problem. Burnt Valve [...]
Hi Justin,
Someone linked to one of your posts on Subaru Outback Foums, and it sounds like the problem I have. The other day my car started running rough, but I have been noticing a drop in power for a while. (Not a big drop, but still not as much pep.) To make a long story short, my mechanic said that I have two burnt intake valves on the number 4 cylinder. (I live in San Diego, otherwise if I was up where you are, I’d take it to your shop. You really sound like you know what you are talking about.) From what you know, if I only fix one head, will I be ok for a while?
Any suggestions would really be appreciated.
Hi Joe,
We usually check out both Heads most of the labor is in taking the engine out and getting it apart, once one side is off its really not much more time to take the other side off and be thorough. I will also suggest that the injectors need to be cleaned.
Justin
Sorry I didn’t get back sooner, but I forgot how I got to your site. The shop did offer to pull the other head, but since I am going into the hole to get one side fixed, and I was thinking about selling the car, I passed on the other side. The mechanic said the compression on the other side was like new, so maybe I got away “cheap” this time.
I purchased my 2005 Baja in June of 2004 and I have loved it, treated it right and had it serviced at Subaru of Richmond religiously ever since.
On Friday evening I was told my Baja would cost btwn $4300 -$4700 to repair and take 2 weeks or more due to burnt valves…….I am shock.
This because of a symptom in my Baja that I started trying to research over a year and a half ago
In August 2010 on a routine service visit I complained of a jerking feeling while driving – they found no codes & unable to duplicate it, released it back to me.
June of 2011 during another routine maintenance I had them research an erratic idle – they found no codes.
November 11th of 2011 asked service to research the “Check Engine” light – my receipt shows they found a misfire on Cylinder 4, could not duplicate and cleared.
November 18th of 2011 – I RETURNED TO SERVICE to again research the “Check Engine” light – my receipt shows they found a misfire on Cylinder 1 & “cleared at no charge to customer”
Now on February 17th I was informed that they must replace the valves on Cylinder #4 and I am unable to drive the car or I may cause another $1000 dollars damage to the Catalytic Converter.
I just cannot believe this has happened to me with a Subaru – I know this is not supposed to happen.
WTF
Hello Kim,
Based on the age of the vehicle when you reported the first instance of cylinder misfires it was out of warranty the at the first instance. Its hard for me from here to tell you if a fuel injection service would have helped you avoid this issue back in 2010 or earlier. You didn’t mention if the vehicle jerked anytime between August 2010 and June 2011? Codes and symptoms don’t always correlate and if the symptoms persisted you really needed to keep taking it back until it was diagnosed and repaired.
I will say however that intermittent misfires are difficult to diagnose, which is why you were not charged. Another way to approach this would have been to say “we need to tear into this to figure out what is wrong, and we don’t know how much it will be until its apart and we know the exact cause of the misfire”. The problem here is that no one wants to ever hear “the truth” so instead lights are cleared and cleared and cleared until it is more obvious what is wrong. That is the Auto repair industry and it just wont ever change.
Based on your post you have most likely had a valve issue since at least November of 2011 but unless I am missing something the cost to repair would be the same.
Yes it does need to be repaired, not just because of the potential Catalyst issue but more importantly that misfires are hard on rod bearings as well.
I know this doesn’t help take the sting out the estimate, but even though we have made this repair on a few Subaru’s it is not wide spread and I highly doubt you would have a second occurrence.
Justin
Hi,
I recently had a burnt exhaust valve on the no. 4 cylinder. The dealership did the valve job and it seems fine after about 2,000 miles. My concern is they never were able to give me any explanation of what caused the problem to begin with. They simply said something along the lines of “it happens” After coming here it seems like I could have an issue with injectors that could result in a repeated burnt valve. Is this something I should look into right away or could it wait until my next service.
thanks,
Andy
Hi Andrew,
Yes they fix whats broken and give no thought to why in many cases.
It would be good preventive maintenance to have a fuel injection service performed, and inquire to if the Dealer logged any cold morning misfire data on all other cylinders.
Hope that helps
Justin
[...] These motors are susceptible to burnt exhaust valves due to some issue with the fuel injectors. I suspect that is the problem and not a sticking piston ring. The engine head would need to be pulled and the damaged valves would need to be replaced. I would not expect that to be cheap, maybe $2000. It might be a good idea to have all of them inspected in case there are issues with other cylinders. Subaru Repair Seattle, Subaru Service Seattle – Seattle Subaru Repair [...]