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'18 Tacoma, '16 Legacy, '04 Outback, ''73 MGB Roadster
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Discussion Starter #1
Hi all, my '04 OBW, 164k miles, has developed an annoying stutter. Starts after it's warm, noticeable under light to medium throttle,at any speed. Feels like a mis-fire, but throws no codes. Coil and wires not too old, dealer items. Throttle body recently cleaned, engine idles perfectly. I'm guessing EGR, because the stuttering, fluttering, mis-fire-feeling happens at the times the EGR might want to be active. I've chased and remedied malfunctioning or dirty, sticking open or closed EGRs in older cars, but since this one is tied to the computer, it doesn't like being disconnected, in an effort to isolate it. I have it out of the car right now, and I'm soaking it, in an attempt to clean it. The plunger for the most part moves freely, just a little sticky trying to open it. And of course, you can't really get into the pintle/seat area, to scrub or scrape it. I'll assume the electrical part is fine, as when it's connected, there's no codes, and when you disconnect it, it throws a few codes. I'm wondering if I can install the valve, leaving the solenoid off it, but plugged in, so the computer sees the solenoid, maybe even activates it, but it just won't open.
A little long-winded, but thanks for taking the time!
 

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Lawn ornament XT
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I had a bad EGR valve in my '98 that gave me a persistent P0400, but I never noticed a driveability symptom.
 

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2012 OB , 2017 Impreza
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*) Can EGR go bad? -- YES
*) Can EGR fail without throwing code? -- YES
*) Does EGR fail on Subaru? -- YES (I am aware of several late 90s outbacks failing)

From reading your post, you have not actually PROVEN that the EGR is the problem. You have made a reasonable assumption... but nothing more than that.

Can you try PLUGGING the EGR pipe so the exhaust gas cannot get into the intake manifold? If this makes the stuttering problem go away, then you would have a better idea that you are on the right track.
 

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'18 Tacoma, '16 Legacy, '04 Outback, ''73 MGB Roadster
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126 Posts
Discussion Starter #4
I re-installed the valve body, but left the solenoid off, but plugged in. Started the engine, no codes. I raised the throttle while depressing the plunger, and got the same symptom. Is the valve OK, and solenoid bad? Or is the valve and solenoid OK, and the computer telling it to open, possibly too wide, at inappropriate times? The struggle is real....
 

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2012 OB , 2017 Impreza
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Is the valve OK, and solenoid bad?
If you can 'manually' open/close the valve and detect a difference the way the engine runs.... I would assume the valve is working.

Or is the valve and solenoid OK, and the computer telling it to open, possibly too wide, at inappropriate times?
To answer this, you may need an OBDII reader. Using such a device, you can monitor the signal that the COMPUTER is sending to the EGR valve.

Another way I might look at this would be to put a voltmeter across the EGR solenoid terminals and monitor the voltage being sent to it as the throttle is opened.

It is also possible that the INSIDE of your intake-plenum has a heavy layer of carbon where the EGR feeds into it. I know that on some VWs, the intake-plenum gets so carbonized that it has to be removed and a torch used to burn-off the layer of carbon.


Another idea: What if your exhaust is somehow partially plugged and when the EGR opens, too much pressure is fed into the intake-plenum?
 

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'18 Tacoma, '16 Legacy, '04 Outback, ''73 MGB Roadster
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Discussion Starter #6 (Edited)
To answer this, you may need an OBDII reader. Using such a device, you can monitor the signal that the COMPUTER is sending to the EGR valve.

Another idea: What if your exhaust is somehow partially plugged and when the EGR opens, too much pressure is fed into the intake-plenum?

Interesting thoughts...
My cats are only a few thousand miles old, and judging by the way the car runs otherwise, I don't suspect the exhaust being part of the equation. The valve body itself wasn't horribly carboned up, and when manually depressing the piston, it reacts exactly as I would expect. I'm going to drive the car tomorrow, see how it behaves, with the solenoid plugged in, but uninstalled.
You mention a code reader. I have an Ultragauge plugged into the OBDII port, tells everything you might want to know. MPGs are right where they belong, if not a little better than the window sticker advertised. I also have a decent, but now old reader, but, like I've stated, it's not throwing any codes. Would either the handheld scanner or the Ultragauge be sophisticated enough to show me an impending code? I just don't want to start throwing parts at it, I just wish my diagnostic skills were a little sharper.
Thanks for the input, and I'll post up any results!
 

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2001 VDC/SC One of a Kind
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Is this a 4 or 6?

When the EGR operates, the ECM opens it at cruising speeds, it allows exhaust back in to the intake stream to cool the combustion. At idle and deceleration, the EGR closes. If the EGR is faulty by sticking open, the car will idle poor. If the EGR doesn't open at all, you wouldn't notice that its not operating but the computer will because it judges EGR operation on pressure feedback.

Unless the valve is partially open at idle, your problem lies elsewhere.

Could be air metering from the MAF, dirty air filter, fuel filter, TPS adjustment, IAC valve sticking on the low side(does it idle low?), AF sensor(s), battery, grounding, or PCV valve. These are just a few things. I doubt its the EGR.
 

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Discussion Starter #8
Sorry for the omission, it's a 2.5. I have the EGR valve installed, with the solenoid plugged in, but off the valve. So, essentially, there's no EGR. I drove it briefly this morning, and right about where and when the problem would start, it behaved beautifully. So, I think I've narrowed it down to a faulty solenoid (doubtful), or the computer operating it erroneously. Cardoc, I will pursue the ideas you've suggested, maybe some sensor offering an erroneous input, causing the computer to send an ill-timed command. Stay tuned, and thanks....
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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My '05 forester has had to have the electric EGR valve freed up a few times, symptom was bad idle, ok elsewhere.

Freed right up after removing and disassembling.
 

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'18 Tacoma, '16 Legacy, '04 Outback, ''73 MGB Roadster
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Discussion Starter #10
OK, some research. Drove about twenty miles. Felt great, as I expected, air/fuel charge not diluted with exhaust gas. Not tapping/pinging like I thought it would, given that the intake charge was hotter, not being given the benefit of lower combustion temps due to the diluted intake charge. BUT, it threw the P0400 code, which I was expecting, and it immediately cleared when I used the Ultragauge to reset it. Got home, pulled into the garage, popped the hood, figuring I'd remount the solenoid. It was screaming hot, to the point of not being able to handle it. It was hanging on its cable, resting on the vacuum line to the brake booster, away from the engine heat. I would expect an energized solenoid to be warm, but this hot? Anyway, I'm going to remount it, to prevent any damage, and continue to dig, using suggestions from the contributors to this thread. I'm thinking, maybe grab a couple at the junkyard, do some swapping, possibly isolate the problem. Thanks guys.
 

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Discussion Starter #11
Time for an update. Haven't been driving the car much, but got back to it yesterday. Out of desperation, looked on Youtube for these symptoms, and all the results pointed to the MAF sensor (hats off to cardoc!). Got a can of cleaner, gave the MAF the recommended shots of fluid, and magically, it ran great! I put the EGR back together, and it seems to be behaving! Looking at the prices for a new sensor, the nine bucks for a can of cleaner is a bargain. Thank you to those who've contributed to this thread.
 

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Discussion Starter #12
Update my update. Apparently, my '04 OBW 2.5 has no MAF sensor. It relies in a MAP sensor for operation. Can this be cleaned, or just replaced?
 

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Update my update. Apparently, my '04 OBW 2.5 has no MAF sensor. It relies in a MAP sensor for operation. Can this be cleaned, or just replaced?
My '84 Corvette uses a MAP sensor instead of a MAF sensor. Not much to clean out. Personally if acting up I would just bite the bullet and replace it.
 
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The MAP can be cleaned but you have to be careful doing it. Carbon will get inside the orifice and create a blockage that inhibits the baffle movement and the MAP sends erratic voltage back to the ECM. Subaru only MAP if you decide to replace it as the aftermarket MAPs do not scale at the proper voltage range.
 

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Discussion Starter #15
A bit of an update. I got a MAP sensor from the junkyard, cleaned it with the MAF Sensor cleaner I erroneously bought, and it seems to be behaving. Not perfect, but so much better.
Thanks to all for your responses.
 

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2008 Legacy Wagon, 2.5L NA
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heyhar:
how did you test your EGR valve?
I have an 08 2.5L NA; and I'm not sure if it's a stepper motor or solenoid version.
 

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Discussion Starter #17
As far as testing it, I tried leaving it installed and unplugging it, sets a code.
Take the screws out, to separate the 'motor' from the valve body. Takes a longer while, to set a code.
Unplug the one on the engine, plug in another. Computer figures it out, sets a code.

I was convinced that my problem was the fault of the EGR valve, but through all the combinations of testing/isolating the EGR 'solenoid' and its accompanying valve, the one thing that remained constant was the skipping/stuttering/shaking of the engine. I sort-of figured that the EGR was in-fact operating normally, as without it operating, the engine would ping/valve-tap, because the intake charge is calibrated for a little 'spent' EGR exhaust gas, and when it was missing the cooling effect of the spent gasses, the combustion temp tends to rise, causing a pinging episode.

So, I set my sights on the MAP sensor, and cleaning and swapping among the few I've gotten from the junkyard has, at least to my mind, convinced me that this little critter is what's at fault. Warmer weather and less overtime may make it easier to prove my hunch.
 

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06 OBW 2.5, 05 Forester, had 03 H6 OBW
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It was stuck hard so bad all the time.
Something like that could be sticky sometimes only.
 

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Discussion Starter #20
Well, a bit of an update. The fluttering, hesitating, general undrivability got a lot worse. I'd dropped the exhaust after the cats, seemed to run better, I wad due for a new exhaust anyway, so it got replaced. It ran until it didn't. Took it to a mechanic to have it scanned, and the ECU wouldn't display some functions. He did find a wonky injector, so they were replaced. New crank sensor, plugs, wires, too. Still crappy. I took it to another mechanic, he plugs in his Snap On diagnostic tool, immediately finds pressure, not vacuum, in the intake. I guess my new MAP sensor is working!. I came home, removed the EGR, and it was jammed open! Made a temporary block-off plate, the engine behaved, but with a slight misfire. I went back, and he said to try Techron, the black bottle. I followed the directions, and within a tankful, the misfire was gone. So, now I'm back to a running car, with the same annoying stutter.

Long story short, I looked on YouTube for videos on bad knock sensor. I unplugged it, and the problem was gone!
Seems as though it was the problem all along. So, I ordered a new one, should be here this week.

It never threw a code, other than when I unplugged it. I'd like to know how they operate. Disconnected, no jerking/stuttering, but it did feel a little down on power. Does the sensor allow the timing to advance until it detects whatever it's listening for, and then retard the timing until the noise is past? And without it connected, does the timing default down to a safe level? I'd really like to understand this process a little better.

Thanks to all for your responses, and putting up with my graphic novel!
 
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