Cylinder misfire CEL

[xt2005bonbon]

I did change my air filter when I did my plugs. The old one looked moderately dirty but not too bad. I have not cleaned my MAF sensor, but I'll look into it. Did you have some luck with that? *crosses fingers*

 

That's my next bet until I can do the comp test. My filter has not been changed since 30000 miles . See pics of the filter here: http://legacygt.com/forums/showpost.php?p=4282030&postcount=45

 

I hope that'll be it. It'll take me some time to get a new filter as there are none available where I live. How's your car acting up so far?

 

Have you read this thread as well: http://forums.nasioc.com/forums/showthread.php?t=2318069

[deltasierrahotel]

My car is making me scratch my head. Lately it seems like sometimes I start it up and it runs like it's brand new, all the way from cold to fully warmed up. Other times, it seems rough right from the get go and I get a solid (or even flashing) CEL during my drive. If it flashes I pull over immediately (since I'm told this means it's dumping raw fuel directly into my cat) and turn the car off for a couple minutes, then start it again and it stays solid. Occasionally the CEL will even go off while I'm driving after being on for few miles.

 

There's less of a correlation between misfires/rough idle and a cold engine than there used to be. Now it just seems like sometimes I start it and it gets off on the right foot and decides to have a great day and other times it wakes up hating the world. I can sympathize, but I can't say I understand this kind of behavior from a machine.

 

I hadn't seen the NASIOC thread, but here's something interesting on there:

 

"10. Lightweight flywheels or crank pulleys. (phantom misfires) Can cause false misfires. Opensource tuning can disable."

 

I just had a new clutch put in and switched from the OEM dual mass flywheel to a single mass Exedy flywheel that came with my clutch kit. As I understand it, this is the same clutch kit that comes stock on later LGTs with the same engine, but maybe they are tuned differently to accommodate it?

[xt2005bonbon]

interesting. I can't really comment on the use of lightweight flywheel and its effect on misfires. I would do more searches over on NASIOC to see what they say about it.

In my case, I do have a lightweight Perrin crankpulley. But it's been on for 30k. So I doubt it's it for me.

[Max Capacity]

FWIW, you don't want these cars on the factory tune. It does have flaws.

 

Are either of you on a custom tune ?

 

If not I highly recommend it.

[xt2005bonbon]

FWIW, you don't want these cars on the factory tune. It does have flaws.

 

Are either of you on a custom tune ?

 

If not I highly recommend it.

 

I am not. Waiting on getting a vag-com cable. I do want to get it tuned. But it'll have to be a remote tune .

[deltasierrahotel]

FWIW, you don't want these cars on the factory tune. It does have flaws.

 

Are either of you on a custom tune ?

 

If not I highly recommend it.

 

I am on a factory tune. I'm thinking I will get some tuning help per your suggestion, Byron, but I want to figure out my misfire problem first. If my car gets torn apart I will likely put in a catless up-pipe as you suggested. I'm guessing that's something that needs to be accounted for in the tune?

[deltasierrahotel]

I'm trying to get an appointment at Rallispec to sort out my problem. I'll talk with them about tuning while I'm there, if I'm lucky enough to get in.

[Max Capacity]

The catless up pipe does not need a tune just the 2.2k ohm resistor from radio shack inserted into the connector on the shock tower where the EGT porbe is no longer there.

 

Or a custom tune will delete the cel any way's.

 

If you can send a log to the Tuner, he may be able to help you find the problem causing the miss fire.

 

http://www.tuningalliance.com is my Tuner.

[Max Capacity]

I'm trying to get an appointment at Rallispec to sort out my problem. I'll talk with them about tuning while I'm there, if I'm lucky enough to get in.

 

That should work too.

 

Good Luck, I hate electrical problems.

 

 

I think the miss fire could be a result of burnt valves. The OEM tune is known to cause that issue.

[deltasierrahotel]

Yeah, if it's a valve problem it's a valve problem and I'll pay to have it fixed, but I don't want to go through pulling my engine and find out thousands of dollars later that it's something simple like a dirty MAF sensor.

 

As a side note, what do you guys think about Seafoam? The thread xt2005bonbon posted (http://forums.nasioc.com/forums/showthread.php?t=2318069) recommends it for removing carbon deposits.

[deltasierrahotel]

SMFW can cause some random misfires, you can disable the individual codes in the map but i don't recommend it

 

Does it actually cause misfires, or does it make the car think it's misfiring? Lots of other folks have this clutch kit, so I'm thinking it's a long shot, but my CEL did happen the same day I got my new clutch.

[Max Capacity]

SMFW can cause some random misfires, you can disable the individual codes in the map but i don't recommend it

 

I thought that was a LWFW not just a single mass.

 

My Spec LWFW is 17lbs, if I remember right.

 

Oh yea, Seafoam can't hurt.

[deltasierrahotel]

I thought that was a LWFW not just a single mass.

 

My Spec LWFW is 17lbs, if I remember right.

 

Oh yea, Seafoam can't hurt.

 

This is the clutch kit I have in there: [ame=http://www.amazon.com/EXEDY-FJK1001FW-OEM-Replacement-Clutch/dp/B002EO2YR2/?tag=vglnkc6475-20]EXEDY FJK1001FW OEM Replacement Clutch Kit : Amazon.com : Automotive[/ame]

 

I may have referred to it as lightweight and that's probably incorrect. It's whatever the replacement single mass flywheel is that comes with the Exedy FJK1001FW kit.

 

Is there any chance carbon build up on the valves could cause intermittent misfire issues like the one I'm having? [ame=http://www.youtube.com/watch?v=u2OvepyYkGE]Also, there's a video here showing where to use Seafoam on a 05 LGT.[/ame] Does that look right to you?

 

I just talked to Dave at Rallispec in NJ. I have an appointment there for Tuesday morning. Per the recommendations of multiple members on this forum, I want to get a second opinion before I go tearing my engine apart assuming it's a burnt valve.

[deltasierrahotel]

carbon buildup can cause misfires due to valves unable to properly seal for an air tight seal. though a leak down would confirm this with a leak of greater than 10% loss

 

Well, I did have a leakdown test, but it showed 5% loss on #4.

[tdelker]

Then you don't have an issue with burnt valve. Could be a carbon hotspot causing a misfire potentially, but it's a long shot.

 

I would get the cable and do some data logging of MAF, O2, Crankshaft position sensor, etc, and see if someone on here can help you make sense of it all.

[deltasierrahotel]

so then that's not it.

 

Ringland?

[xt2005bonbon]

Were they able to track down where the leaking air was going?

[deltasierrahotel]

If they were, they didn't mention it.

[xt2005bonbon]

I guess it is good news then! If you still have a gut feeling on a potential ringland issue, then watch carefully your oil consumption. That's what I'd do. Time for a tune!

[deltasierrahotel]

I guess it is good news then! If you still have a gut feeling on a potential ringland issue, then watch carefully your oil consumption. That's what I'd do. Time for a tune!

 

I don't have a gut feeling about a ringland, necessarily (except for Murphy's Law) but I do wonder what is causing this problem in the first place. It seems like there has to be a bottom line reason for the misfires outside of the tune. As Byron mentioned, the stock tune may cause burnt valves. But the tune itself won't just suddenly result in misfires when everything has run fine for 95,000 miles, right? I'm planning on getting some help with tuning, but I think we have the same, or maybe different, underlying issues here that need to be addressed.

 

Would you agree? Byron, would you agree? Could this really all just be fixed by a tune? I'd love it if that were true, but...

[xt2005bonbon]

Are they going to put your car on a dyno? I am still a noob when it comes to tuning; but I'd say that they'll be able to see exactly how the car is performing. They'll track tons of parameters which will probably (and hopefully) help find the reason why you're getting these frustrating misfires.

[deltasierrahotel]

I'm not sure what the guys at Rallispec will do. I'm going to take my car to Dave on Tuesday, explain everything that has happened to this point and beg him to impart his wisdom to me on how to proceed. I'm guessing he'll do a second compression test since the first one at the dealer was irregular. I don't think I need another leakdown test, there's no reason I know of to doubt the results I have from the dealer on that.

 

I'm a total noob tuning-wise as well. I'm sure I'll be learning a lot more in the coming months, whether I like it or not. I'd really prefer not to mess with too much in the tuning department, I just want to eliminate any flaws in the stock map and smooth out the power delivery a little, if possible, with minimal risk. I'm not really looking for anything in terms of increased peak performance. It's plenty powerful for my purposes. I just would like it to run without misfiring and have a smoother power delivery curve.

[ScottFW]

SMFW can cause some random misfires, you can disable the individual codes in the map but i don't recommend it

FWIW the OEM SMFW from the 06+ WRX hasn't caused me any issues with misfires.

 

Does it actually cause misfires, or does it make the car think it's misfiring? Lots of other folks have this clutch kit, so I'm thinking it's a long shot, but my CEL did happen the same day I got my new clutch.

When my TOB seized, it was so grindy and rough when I let out the clutch pedal that the car threw a misfire CEL. So it is possible to get misfire codes from something other than a misfire. But if your engine is actually running rough, it's not a false code. The stock DMFW is so damn heavy that it masks a lot of engine vibrations. It's possible your new lighter flywheel simply lowered the threshold for the ECU to detect legit misfires.

 

You can diagnose quite a bit yourself with a vag-com cable, Romraider, and Learning View. The P030x misfire code will tell you which cylinder (x) is tripping the CEL. If you fire up Romraider you can watch the "roughness" parameter for all 4 cylinders simultaneously. BTW, roughness is one of the "extended parameters" that only shows up while you're connected to the car's ECU, so you won't find it in the list if you're just playing with the software on your living room couch. Anyway, you can watch to see if it's just one cylinder misfiring or if others are showing counts of roughness. At hot idle I'd get an erratic bumpiness that wasn't quite bad enough to throw a misfire CEL, but it did show roughness in Romraider, only on cylinder #1, so that really helped me narrow it down.

 

If it's one cylinder, try swapping that cylinder's fuel injector (especially if your learning view shows rich LTFTs) to another cylinder and seeing if the misfire moves with it. If not, try swapping the coil. Mine did turn out to be a scuzzy injector, because when I cleaned it and then swapped the #1 and #3 injectors the bumpy idle and logged roughness in Romraider disappeared completely (with no ECU reset and no other changes to the car) and my LTFTs aren't as rich either.

 

My reading tells me that the fuel injectors on these cars can get crappy over time and around 100K miles is a common time for that to happen. My car has 99K. The two injectors I pulled had a little varnish around the nozzles that could have been affecting the spray pattern. If they get gummed up enough so they don't flow enough, you will get misfires. Those will show up at idle first, because the pulse width is very short. If it gets to the point that you're constantly misfiring and running lean, you will burn valves.

 

If you have good compression and no or minimal oil consumption, you probably don't have a cracked ring land. If you have good leakdown, you haven't burned a valve yet, but you could be on your way to that if one or more injectors are at fault and you don't deal with it soon. I will be sending mine in to Deatchwerks pretty soon here based on the results of my injector swapping diagnostics.

 

This is all assuming you have decently fresh spark plugs and have already cleaned the MAF with a $5 can of the CRC spray, and have looked for and corrected any vacuum leaks.

[deltasierrahotel]

Scott,

 

Thanks for the advice. The plugs and air filter were the first thing I did, and I swapped coil packs at the same time. When that didn't work I swapped fuel injectors but still had a misfire on #4. I also tested with carb cleaner, but have not replaced, the intake manifold gaskets on the driver's side. Sad as this sounds, I have not cleaned the MAF or even thought of it until xt2005bonbon suggested it this morning. So I'm stopping at Advance Autoparts on the way home for some CRC MAF cleaner. If that turns out to be the problem I'd be ecstatic.

[ScottFW]

My MAF had just a slight film on it, and cleaning it didn't do squat for making mine run better. It's something that should be done to help eliminate that as a contributing factor, but I wouldn't expect miraculous results especially if it's just one cylinder misfiring.