Just another misfire/rough idle thread...

[Diamonddice6]

I took the car to the mechanic shop who suggested change the catalytic converter, after doing that... the car running normal with no missfire...i will drive the this week to make sure there's no more missfire.

 

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[StkmltS]

I took the car to the mechanic shop who suggested change the catalytic converter, after doing that... the car running normal with no missfire...i will drive the this week to make sure there's no more missfire.

 

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That'll be awesome if it fixes your problem!

 

Which cat got changed? Did your mechanic say why it needed changed? That seems like an unusual diagnosis for a misfire.

[xt2005bonbon]

that'll be awesome if it fixes your problem!

 

Which cat got changed? Did your mechanic say why it needed changed? That seems like an unusual diagnosis for a misfire.

 

+1

[heiche]

Interesting that a bad cat caused misfires in cylinders 3 and 4. Kinda makes sense I guess if excessive exhaust backpressure causes the misfires, what with our interesting firing order and exhaust config.

 

Since the firing order is 1-3-2-4, maybe when the pass side bank fires 1-3 in a shared exhaust runner, 1 has a little room for the exhaust pulse, but it builds up pressure against the clogged cat, then cyl 3 observes high backpressure and misfires. Then there's a rest before these fire again.

 

Likewise, then the driver side bank fires 2-4 into its shared exhaust runner. This time 2 fires ok but starts to build pressure against the clogged cat, then cyl 4 observes high backpressure and misfires.Then there's a rest before these fire again.

 

Not sure if that makes sense - just trying to work out why 3 and 4 would be victims of misfires with just one common cat being clogged. I guess if it got any worse, eventually all cylinders would misfire under load. Especially when the cat warms up.

[StkmltS]

^ That sounds like it would work in his situation.

[StkmltS]

So I took my car on a 600 mile trip two weeks ago, and I've been driving it daily since then. Prior to my valve adjustment I was getting a CEL every other day, sometimes multiple times per day. Since I last reset my ECU 750 miles ago my CEL hasn't come on. My last 150 miles have been strangely problem-free*.

 

My misfire is still audibly present (BtSsm confirms) but my low idle problem is completely gone. As best as I can remember it hasn't tried to stall even once since I got back from my 600 mile trip. Until recently, it was bad enough that I almost dreaded driving the car because I was fed up with it stalling in stop-and-go traffic, at stop signs, traffic lights, intersections, etc.

 

- My LVs indicate that I probably have a vacuum/boost leak somewhere... or a crappy cylinder.

- Per my borescope pics my cylinder #2 looks pretty healthy.

 

Could it be that my engine has just now become familiar enough with the adjusted valves to keep away the low idle? I kinda want to reset my ECU to see if the idle problem will come back but then driving the car will be unpleasant again.

 

If my low idle doesn't come back I'm just going to get the car off the stock tune and be cautious and drive it as-is.

 

Any open source tuning recommendations? For now I'm going to be very conservative and do it all myself as I learn along on the way. My plan is to use an already proven map that doesn't require any supporting mods, and slightly tweak it for my car. I'm not looking for more power, I just want to take everyone's advice and get off the stock map.

 

*Oil is still leaking from my OCV and smoking just enough to stink up the area whenever the car isn't moving, but that's totally unrelated and nothing's fault but mine.

Edited August 3, 2015 by StkmltS

[heiche]

Glad to hear there is some improvement. So these days, what sort of misfire counts are you typically seeing?

 

When you say they are audibly present, does it have a constant beat? Or is it an occasional muffled pop sound?

 

Regarding tuning, I use RR to do all of the editing. And a Tactrix OP 2.0 cable (and corresponding ecuflash software) to actually flash the ECU. Tuning is a vast subject, but you can start with a few things. For example, I would suggest removing the Closed Loop to Open Loop delays. That's often what people are referring to when they say the stock tune burns exhaust valves. See the first section "Closed to Open Loop Delay" in this post for example.

[StkmltS]

Glad to hear there is some improvement. So these days, what sort of misfire counts are you typically seeing?

 

When you say they are audibly present, does it have a constant beat? Or is it an occasional muffled pop sound?

 

Regarding tuning, I use RR to do all of the editing. And a Tactrix OP 2.0 cable (and corresponding ecuflash software) to actually flash the ECU. Tuning is a vast subject, but you can start with a few things. For example, I would suggest removing the Closed Loop to Open Loop delays. That's often what people are referring to when they say the stock tune burns exhaust valves. See the first section "Closed to Open Loop Delay" in this post for example.

 

That stock-ish map is exactly what I've been looking for, thanks for the link!

 

My misfire sounds like a muffled pop.

It's sporadic and without a noticeable pattern, but it's consistent enough to be heard once or twice every second or two. The frequency could be compared to an automatic gun set to fire 2- or 3-round bursts. I'll try to take a video of it tonight. My small exhaust leak makes it pretty easy to hear.

 

My typical misfire count for cyl#2 is anywhere between 4 and 8, but sometimes far less.

Strange things is, it only occurs below 3k RPM. Is that a limitation of my ECU/sensors, or does it really stop >3k? .

 

Link here for the csv file.

In this particular log I have knock, most of my other logs show knock at zero.

 

Real numbers from today (15,267 data points):

Cyl#1 is misfiring 0.000% of the time (0/1,5267)

Cyl#2 is misfiring 9.792% (1,495/15,267)

Cyl#3 is misfiring 1.827% (279/15,267)

Cyl#4 is misfiring 0.210% (32/15,267)

Edited August 3, 2015 by StkmltS

[xt2005bonbon]

fyi and from my experience, the misfire CEL will be thrown if the roughness misfire counts goes like 35+ several times in a row. Below that, the CEL is usually not thrown.

 

Also I can't remember if you mentioned this before, but did you recheck your valve clearance once the timing belt was in place right before you put the valve cover back? Maybe it is still a bit off?

 

What are you LT fuel trims btw?

[StkmltS]

fyi and from my experience, the misfire CEL will be thrown if the roughness misfire counts goes like 35+ several times in a row. Below that, the CEL is usually not thrown.

 

Also I can't remember if you mentioned this before, but did you recheck clearance once the timing belt was in place right before you put the valve cover back? Maybe it is still a bit off?

 

What are you LT fuel trims btw?

 

I forgot to check the valves after putting the belt back on (shaming begins... now).

See LV in post above (I added it as you replied).

[xt2005bonbon]

Mmh. maybe recheck the clearance? I know it sucks to do it again but you know.. I forgot though: do you get this count at idle regardless of engine operating temperature?

 

Also, yeah your trims are way off. did you check for vacuum leaks? Values should say within +/-5% (mine, for instance, have been staying right around +/-0.5% all across the board for the past month).

[StkmltS]

Engine temp has zero affect on the misfire. With a fully warmed motor I've driven to point A whilst fighting a terrible idle, parked at point A for 5 minutes without turning the engine off, and then drove to point B with the idle mysteriously perfect.

 

Ain't no way I'm taking off the valve cover again (yet). I sheared off one of the bolts when I put it back on after my valve adjust-a-roo and I don't want to push my luck asking it to seal correctly again without extracting/replacing the bolt.

 

I DIY smoke tested it once and found a leak coming from under the intake manifold on the driver's side. I didn't fix it because I couldn't get to it and I couldn't see exactly where it was leaking. Now that I have a borescope I may smoke it again and use the camera to find the exact location of the leak.

[xt2005bonbon]

I DIY smoke tested it once and found a leak coming from under the intake manifold on the driver's side. I didn't fix it because I couldn't get to it and I couldn't see exactly where it was leaking. Now that I have a borescope I may smoke it again and use the camera to find the exact location of the leak.

 

It could be that the intake manifold gasket isn't sealing properly. Don't know if you know about it, but Subaru changed the gasket design so it seals better. Several people have reported issues with the original old design gasket, and had to change them to the newer kind. Worthwhile to check it out at least.

[StkmltS]

Changing all four of the IM o-ring gaskets was my first attempt at fixing the misfire.

[xt2005bonbon]

OK. Then yeah, take another good look at that leak.

[StkmltS]

2 seconds after starting my car after work.

Great, now even BtSsm is telling me "ynansb".

 

http://images.tapatalk-cdn.com/15/08/03/e3fefb39936db62bc6d648875eb5f1d9.jpg

 

Sent from inner space.

[xt2005bonbon]

Lol that's a good one. Timing ever so slightly off? My first guess anyways...

[heiche]

MrTris himself requested that one - specifically for cyl 4

[StkmltS]

Screw cylinders #1-4, screw turbos, screw misfires, screw banjo bolts, screw Porsche, screw the internet as a whole, screw Tris (RIP), screw #ynansb, screw me, screw BtSsm (with all due respect), screw Subaru of Ameria, screw the state of Indiana, screw Henry Ford, screw the new Corvette, and especially screw my car.

 

Why me, whyyyyyyyyyyyy!

 

Sent from inner space.

[heiche]

can you use your last bit if hope to fix that leaky throttle body hose? maybe that will help?

 

or you can use this as an opportunity for a shiny new engine. pm riderdude125 and he can ship a long block to your door that's nearly ready to drop in.

[StkmltS]

My throttle body hose is good to go. Smoke from the leak I couldn't locate was exiting the motor from somewhere underneath the manifold and it was creaping out where the manifold splits for cyls 2/4 (diagram in post #1). I've checked and rechecked the T fitting and surrounding hoses under the IC.

 

Everyone says our plastic manifolds don't crack, but if there was a crack I imagine that smoke would leak out just like it's doing on mine.

 

Riderdude125... I'll look him up.

My Christmas bonus can't come soon enough.

 

Sent from inner space.

[Diamonddice6]

That'll be awesome if it fixes your problem!

 

Which cat got changed? Did your mechanic say why it needed changed? That seems like an unusual diagnosis for a misfire.

The car is running normal till now, no misfire codes, the catalytic converter was badly broken and the small chips were moving to the part after which i am not sure what they call and block...that's why the car was running good in first minute till accumulation of gas in the blocked catalytic converter...which caysing a back misfire...that was the explanation by the mechanic.

He changed the first two with Walker from Napa for $499 and the oxygen sensor for $150...plus his labor fee.

 

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[Diamonddice6]

Interesting that a bad cat caused misfires in cylinders 3 and 4. Kinda makes sense I guess if excessive exhaust backpressure causes the misfires, what with our interesting firing order and exhaust config.

 

Since the firing order is 1-3-2-4, maybe when the pass side bank fires 1-3 in a shared exhaust runner, 1 has a little room for the exhaust pulse, but it builds up pressure against the clogged cat, then cyl 3 observes high backpressure and misfires. Then there's a rest before these fire again.

 

Likewise, then the driver side bank fires 2-4 into its shared exhaust runner. This time 2 fires ok but starts to build pressure against the clogged cat, then cyl 4 observes high backpressure and misfires.Then there's a rest before these fire again.

 

Not sure if that makes sense - just trying to work out why 3 and 4 would be victims of misfires with just one common cat being clogged. I guess if it got any worse, eventually all cylinders would misfire under load. Especially when the cat warms up.

That was my question too when the mechanic told me it is the catalytic converter....why not all clynders and just 3 and 4....no logic explanation however the catalytic converter was badly broken from inside....it has a big whole and rattling sound....so i had to replace if it is the cause or not.....but the funny thing ....the car passed the immition test couple months before this issue happened !

 

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[heiche]

just referencing this post since it has some good pics of the intake manifold. wonder what could be leaking? could u post a video of another smoke test?

[xt2005bonbon]

^ +1.