Very rough idle. - 1/15/09, P0304 code shows up :(

[KAG]

Update: Weeks later, a code finally pops up. It's a P0304, cylinder 4 misfire code.

Over the past few months my 2000 BE (sohc ej25) has been idling a lot rougher than it should be, and everything I've done to try to fix it hasn't worked. So, my question is, what could be causing this?

Here are the details:

- Once I give it gas, the roughness goes away and it runs like a champ.

- I've replaced the spark plugs, plug wires, air filter, fuel filter, and pcv valve. None of which made any difference in idle.

- I've cleaned the intake and throttle body, reset the ecu multiple times, and even ran a full diagnostics test which showed everything healthy as it should.

- I ran a compression test and all four cylinders showed 160psi.

- I've checked every single one of my vacuum hoses and fuel lines - nothing out of place.

Last night when I was changing my oil and checking on a few things I heard something that I'm not entirely sure if it's normal or not. When I give it gas, it makes kind of a clicking sound before revving up. I took a video of it found here: http://s445.photobucket.com/albums/qq18 ... u031-1.flv (http://s445.photobucket.com/albums/qq180/kgod2000/?action=view&current=subaru031-1.flv)

It sounds ignition related, but I could be wrong. The only other things I thought could cause the roughness would be fuel pump related - or maybe an injector? I'm all out of ideas...

Any input is appreciated. I'm pulling the motor out over winter break to do the clutch so I'll be able to check everything then too, but the sooner I figure this out, the better.

Thanks,
Kyle

[Huffer]

I didn't see where you cleaned the Idle Air Control Valve...?

[KAG]

I didn't see where you cleaned the Idle Air Control Valve...?
All of the symptoms seem to lead to the IACV, but I cleaned it when I cleaned the throttle body and it didn't do much of anything.

The little clicks when I give it gas are really bugging me. It sounds like it's coming somewhere around the throttle body, but I just can't pinpoint it enough to find out exactly where it's coming from.

:dontknow:

[97legacygt]

Just an idea, maybe the throttle cable/ mechanism is hitting on something when you rev it causing the click. But that wouldn't explain the rough idle at all, so who knows.

[birukun]

Is it a metallic 'click' or electric 'tick'?

[KAG]

Is it a metallic 'click' or electric 'tick'?
It sounds to me like an electric 'tick'. You can hear it in the video every time I give it gas.

Also, it's been getting colder and colder every night here in Cali (down to 25 degrees here in the morning, that's VERY cold for where I live). When I go start up my car in the morning, it makes a long, weird winding sound that sounds like an extended version of the 'tick'. It takes anywhere from 3 seconds to 10 seconds for it to go away. The colder it is, the longer it takes. Any other time of day, it doesn't do it - only in the morning.

Me = :smt012

[birukun]

That sounds like a really noisy injector - maybe one is flaky or on it's way out?

[KAG]

I wouldn't be surprised if it was one of the injectors, actually. They've always been that loud, and the guy I bought the car from said it was normal and that it had always been like that. My guess is he wasn't aware of it either. Is there any way to tell exactly which one it is?

I've never seafoam'd the car, I'll try that one day this week and see if it does anything...

[KAG]

I'm going to continue this thread since it's more directly related to the engine than my Exedy clutch thread.

Well, just yesterday the check engine light came on out of no where, and right before I had to leave for a 4-hour trip to the coast. The car drove the same, but I didn't like the light staring at me the entire way.

The code is P0304, which is a cylinder #4 misfire code.

I'm stumped even more now. :-(

[Okin DaVanh]

I'm going to continue this thread since it's more directly related to the engine than my Exedy clutch thread.

Well, just yesterday the check engine light came on out of no where, and right before I had to leave for a 4-hour trip to the coast. The car drove the same, but I didn't like the light staring at me the entire way.

The code is P0304, which is a cylinder #4 misfire code.

I'm stumped even more now. :-(


Check the plug wire?
The spark plug itself?
The coil pack?

[KAG]

Check the plug wire?
The spark plug itself?
The coil pack?
I replaced the wires again today, no difference. I checked the plugs while I was at it to make sure they were gapped correctly. They were replaced less than 600 miles ago. I haven't tried anything with the coil pack yet. I don't really want to buy a new one so I might ask the junkyard if I can try a few out and see if it works or not.

If it's not the coil pack I'm thinking it could be anything like the front o2 sensor, the #4 injector itself, the ecu not functioning properly, or a burnt exhaust valve.

This was the LAST code I was hoping to see :-? Tomorrow I'll have go down to the shop and get the scanner again to read all the data.

[Huffer]

Try some injector cleaner - it could well be a bad injector. The other thing you could do is do a compression test.

[T_F_E]

[color=#FF0000]

- I ran a compression test and all four cylinders showed 160psi.



^ from the original post

[KAG]

Yep, already ran the compression test and all 4 cylinders came back the same. After doing this, I concluded that the motor itself is very, very healthy and the problem is likely electrical rather than an mechanical.

With the injectors, I might try switching two of them. For instance, putting the #4 in the #2 and seeing if the code comes up P0302 instead. If it doesn't do anything, I can cancel out that idea.

[Huffer]

Reading comprehension pwns me. Good idea with the injectors though.

You could also remove the injectors and have them flow-tested. Check things in/around #4 - bad fuel line, bad spark wire etc.

[KAG]

Diagnostics test results:

Engine Speed.............................675 - 725rpms
ECT......................................................183 F
Vehicle Speed........................................0mph
Ignition Timing......................6.0 - 10.0 degrees (was always fluctuating)
Engine Load...........................................3.5 %
MAP (P)...........................................9.6 in Hg
MAF (R).........................................2.95 gm/s
TPS......................................................0.0%
IAT.......................................................93 F
Fuel Stat 1...............................................CL
Fuel Stat 2.........................................Unused
ST FT 1................................................0.8%
LT FT 1...............................................13.2%
O2S B1 S2.........................................0.675 V
FT O2S B1 S2........................................0.0%
MIL Status..............................................OFF

If anyone has experience with this obdII stuff and finds anything on the list that doesn't sound right...please let me know.

The things that I find suspicious are the TPS sensor having 0.0%, the ignition timing, and maybe the o2 sensor. However I have very little knowledge on these kind of things.

FYI: I cleared the check engine light and it did not come back on. Sadly, the rough idle and exhaust sputtering is still there.

[decke48]

Diagnostics test results:

Engine Speed.............................675 - 725rpms
ECT......................................................183 F
Vehicle Speed........................................0mph
Ignition Timing......................6.0 - 10.0 degrees (was always fluctuating)
Engine Load...........................................3.5 %
MAP (P)...........................................9.6 in Hg
MAF (R).........................................2.95 gm/s
TPS......................................................0.0%
IAT.......................................................93 F
Fuel Stat 1...............................................CL
Fuel Stat 2.........................................Unused
ST FT 1................................................0.8%
LT FT 1...............................................13.2%
O2S B1 S2.........................................0.675 V
FT O2S B1 S2........................................0.0%
MIL Status..............................................OFF

timing is a little low. it should run 10-15* at idle. but depending on how the car is set for base timing this could be normal
engine load is normal
map is at normal range for idle.
maf is at normal range for idle
tps should be at 5% at idle but theres no voltage listed to compare at
st ft is normal
lt ft is normal for idle
02 b1 s1 is showing abit of richness but this number should be fluxing rich lean any was
ft 02 is showing a perfect a/f ratio this number should be fluxing up and down

i dont see anything wrong with this. except the tps number is odd but maybe normal. if the o2 is running above .550v alot they may be a spark or fuel issue with a cylinder. if the number is running under .450v alot they may be an issue with a vaccum leak
i really cant tell you anything form a frame shot data log

[Airgne]

KAG,
i have the same problem. it didnt go away until i got my heads re-done. i had #4 exhaust vavles burnt. i think that is you problem.

[KAG]

Thanks for checking that out for me, decke48. Even though it's a frame shot I figured it'd be worth a try to see if anyone could tell me if something was way, way off. On that note, maybe my timing is off?

I should probably change out the front o2 sensor anyways. If (by any chance) it fixes it, hell yes. If not, it'll be good to have it out of the way and in the books for maintenance.

Brandon, I'm going to pretend you never said that :smt002 Burnt valves are a very high possibility, I just don't even want to think about having to pull the motor again and let alone take it apart.

[Airgne]

i did everthing you have and some. even taken it do old school scooby mechanic. couldnt figure it out, and when susbaru pulled the heads to do the gaskets #4 was burnt to shit. i hope its not the same for you.

[Minjin]

My car is seeing some similar symptoms and it looks like this thread was never resolved. I don't see how it could be a burnt valve if all the compression numbers are good.

I can't believe how many people have misfire issues with these cars. And about half of them never seem to get resolved. I'd swear that mine ran better with bad headgaskets than how it does now. That boggles my mind.

[KAG]

Actually, I did get it fixed. The valve lash (clearance) was way off on all cylinders, #4 having no clearance whatsoever.

Runs like a champ now :smile:

[Minjin]

I didn't know these things needed valve adjustments. Does the same thing apply to a 2.5 DOHC?
edit: Nevermind, I answered it myself. Although, my car SHOULDN'T need valve adjustments at only 110k...

[subiman2005]

I didn't know these things needed valve adjustments. Does the same thing apply to a 2.5 DOHC?
edit: Nevermind, I answered it myself. Although, my car SHOULDN'T need valve adjustments at only 110k...

So I have the same problem and have done everything....Injectors coil wires plugs another set of wires lol geez....so whats this valve adjustment and where do I figure out how to check that?

[decke48]

I didn't know these things needed valve adjustments. Does the same thing apply to a 2.5 DOHC?
edit: Nevermind, I answered it myself. Although, my car SHOULDN'T need valve adjustments at only 110k...

So I have the same problem and have done everything....Injectors coil wires plugs another set of wires lol geez....so whats this valve adjustment and where do I figure out how to check that?
need to take off the valve covers and feeler gauge the space between the cam lobe and the lifter bucket. then in the DOHC you need buy shims to get the correct lash

[subiman2005]

I didn't know these things needed valve adjustments. Does the same thing apply to a 2.5 DOHC?
edit: Nevermind, I answered it myself. Although, my car SHOULDN'T need valve adjustments at only 110k...

So I have the same problem and have done everything....Injectors coil wires plugs another set of wires lol geez....so whats this valve adjustment and where do I figure out how to check that?
need to take off the valve covers and feeler gauge the space between the cam lobe and the lifter bucket. then in the DOHC you need buy shims to get the correct lash
Well guess I don't need to check that anymore....did a compression check on that cylinder and wouldn't build past 65 PSI so I am guessing that is my misfire problem!!! Gota love cars when they break!

[KAG]

I didn't know these things needed valve adjustments. Does the same thing apply to a 2.5 DOHC?
edit: Nevermind, I answered it myself. Although, my car SHOULDN'T need valve adjustments at only 110k...
For the record, my car only had 80k on it when the valves needed adjusting.