- This topic has 14 replies, 8 voices, and was last updated 9 years, 4 months ago by
.
-
Topic
-
Hello all. I recently purchased an 02 Subaru Outback LL Bean with the 3.0L H6, 77k miles. It is giving me a P0304 code (misfire cylinder 4). I’m willing to bet it is probably a COP and/or a spark plug. My plan is to replace the plugs and the #4 COP at the same time. Since I don’t know the history of the car, I’m guessing the plugs are a safe bet. Also, the misfire doesn’t seem to rear its ugly head until after it warms up…which also leads me to think the COP is the culprit.
Here is what I have done so far:
Did the “carb cleaner/gee I hope I don’t set myself on fire” intake and vacuum line leak check. No issue found.
Replaced bank 2, sensor 1 AF/oxygen sensor to resolve multiple oxygen sensor codes and a P0420 code. So far this has improved the idle and the O2 and cat codes have not reappeared.
Ran Seafoam through a full tank with 93 octane gas. This also seemed to help.The only outward sign of an issue was a misfire/rough idle once it warmed up. Since the Seafoam and the oxygen sensor, I have the p0304 code reappearing after being erased, but no longer have the blinking CEL indicating an active misfire. Also the idle is a little rough now, but much better than it was.
This car has no acceleration or other issues. It runs like the wind.
Any suggestions other than the COP/spark plug plan of attack?
Also, I have read that Subies in general are picky with spark plugs, and only stick with the OEM (which I believe is NGK). Eric, I know you had a Subaru, but cannot remember which one and which engine. I have no issues buying the best plug out there, but with so many options out there (iridium, platinum, double platinum), I really would like to get the longest life out of them without pissing off my engine. I know typically the rule is “buy the best you can afford”, but just want to make sure “more expensive” isn’t going to cause problems due to a picky engine.
Thanks in advance everyone. You guys are always a wealth of knowledge.
-
Replies
-
The ignition system is designed around the plugs. Because different plugs have slightly different resistance, most newer cars are picky about plugs. Get what ever the manufacturer recommends.
Carb cleaner is nonflammable fyi.
Move that coil pack to a different cylinder, erase the codes, and see if the code changes to the different cylinder. If the misfire code follows the coil pack then it’s a bad coil pack. If the misfire stays on that cylinder you may have another issue.Hello,
I am relatively new to servicing cars. I mainly stick to suspension and some “basic” engine maintenance. I had a similar code that there was a misfire in my cylinder 3. My symptom included slow pick up speed before check engine light came on so I pulled over and went back home to check. I changed the plugs with NGK platinum and the code/symptoms never came back. I didn’t want to pay for double platinum or iridium and didn’t want the cheapest. I usually stick to medium grade.
This happened after I did some basic maintenance of changing air filter, pcv valve, cleaned battery, and cleaned throttle body.
05 Suburu Outback Sport
2.5L H4There are alternative methods for checking for vacuum leaks. You can use water in a spray bottle since carb cleaner is very flammable on a hot engine and may be carcinogenic (contains Toluene, a suspected carcinogen) as well.
Also:
Yes, NGK spark plugs according to info in the video. Double check the owners manual, the placard in the engine bay/underside of hood or the service information, if available.
EDIT/ADD: The above referenced video was produced using a 1997 Subaru Legacy L AWD wagon in which Eric found Autolite plugs. They were replaced with the NGK plugs that belong in it.
I like what I’ve seen in the replies so far. I would add a warning of predestination. There are numerous brands of plugs that claim to have new ways to improve power. Look at plugs like Bosch plus 4 and e3 for example. They have extra meat at the business end of them. That extra meat gets hit after a bit of running and causes detonation before each piston reaches top dead center, acting like a glow plug. This often punches small holes in the pistons causing loss of compression. I know this on a personal level. I have found that the best plugs for longevity and performance are denso or NGK iridium.
Carb cleaner is not flammable at all. Using a spray bottle with water will not find a vacuum leak. Use the plugs recommended by the manufacturer ONLY. Their engineers designed the ignition system around a specific plug so anything else could create a miss. Getting high performance plugs will only benefit you if the entire ignition system is upgraded as well.
[quote=”thisisbuod” post=136789]Carb cleaner is nonflammable fyi.[/quote]
Most carb cleaners are highly flammable and shouldn’t be used for leak detection around hot and running engines to prevent fire. Zep carb cleaner is one brand that I know of that is non-flammable, and there may be others, but most are extremely flammable. Look at the label warnings on the picture below.[quote=”thisisbuod” post=141722]Carb cleaner is not flammable at all. Using a spray bottle with water will not find a vacuum leak. [/quote]
Most carb cleaners, especially those in a spray can, ARE flammable. You CAN find a vacuum leak with water.(water test starts at 7:10)
I’ve always used carb cleaner. All my colleagues use carb cleaner. I think it’s the propellant that is flammable not the cleaner itself. Either way I have never had an issue.
[quote=”thisisbuod” post=141731]I’ve always used carb cleaner. All my colleagues use carb cleaner. I think it’s the propellant that is flammable not the cleaner itself. Either way I have never had an issue.[/quote]
Most of the commercial carb cleaners are acetone and toluene with a propane propellant. All of those components are flammable. But the main point is that it is not important to debate whether it is the cleaner or propellant that is flammable. The important thing is that this is a public forum whose target audience is the DIY general public, who may not be able to make the distinction of cleaner or propellant flammability, and may very easily think all carb cleaners are the same. It is grossly irresponsible and misleading to just say “carb cleaner is not flammable” because then someone could pick up a can that says carb cleaner on it believing it to be non-flammable “because they were told so” and end up with a fireball or more serious consequences.No one I know has ever had a problem with it. It is common practice to use carb cleaner to check for vacuum leaks. I’m not being “irresponsible”by recommending the use of carb cleaner. Mechanics have been doing this for decades. If there was a risk of fire, we would probably stop doing it. Why don’t you chill on the preaching, get over yourself, and get back on topic. You’re not going to change my mind. And I’m going to continue recommending carb cleaner. So just drop it.
I guess you can’t read for comprehension (and probably didn’t watch Eric’s video I posted either). If you notice the PARTS I QUOTED, you will see that the part that I referred to as irresponsible was telling folks that it is NON FLAMMABLE when MOST of those products on the market are HIGHLY FLAMMABLE. It is irresponsible because that can GET SOMEONE KILLED.
I have no reason to watch the video. You saying “it’s irresponsible to say it’s non-flammable” insinuates that it is irresponsible to recommend the use of said product. I can comprehend fine. The two subjects are inherently related. Now just drop it and stop trying to make your argument seem more legitimate by undermining my intelligence. It’s an immature tactic.
- You must be logged in to reply to this topic.