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Scoobymods Guy
2010 Legacy 3.6R Limited
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1,157 Posts
Discussion Starter #1
Just looking for ideas here. Just over the past few days it seems my car has started to stumble when I start the car after it's been sitting for a while. It will idle fine but after I take off in first and get a few feet it seems like the more I press on the gas pedal the more it will stumble. Sometimes it's subtle but it's seemed to get a little worse. Almost like it's starving for gas. If I had a carb I'd say it felt like the accelerator pump was bad. (for you old guys) This isn't a hesitation but a stumble if that makes sense. I may have gotten bad gas but this only happens at the start and then after that it's fine. I changed the fuel filter yesterday and cleaned the spark plug wires up at the coil pack. Today I want to get some TecTron to put in the gas. I haven't driven it today to see if that helped. Just looking for ideas as to what to focus on next that I may have missed. I did the sparkplugs last month and cleaned the K&N panel filter. I checked and I have no MIL codes and my CEL light is not on either.

Thanks for reading,
 

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2000 BRP RS coupe
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351 Posts
I would suggest that you try getting some fuel injector cleaner. I've used some stuff on a few older cars that did perform as well anymore and had some success. At <$10 a bottle, it wouldn't hurt to give it a shot.
 

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646 Posts
It only does it when the motor isn't warmed up and you first start it? I had that happen on a Nissan before with a Cold Start sensor but not sure if the Subaru has the same setup.
 

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Scoobymods Guy
2010 Legacy 3.6R Limited
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1,157 Posts
Discussion Starter #4
I took it for a ride after cleaning the coil pack wires and changing the fuel filter. It still does it, I just put in a bottle of TechTron fuel cleaner well see if this helps. I'm gonna reset the ECU right now and let it sit over night and see if that helps. It apparently will still do it even after the cars been only sitting around an hour or less too. Hummm
 

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79 Posts
Good timing

My 98 RS has started to "stumble" every now and then. Same set-up: car has been sitting, idles fine after starting, give it a little gas and let out the clutch like any other time, and it bogs down momentarily after the clutch completely engages then runs with no problem. I'll be watching for any answers here too.
tasteycow
 

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Scoobymods Guy
2010 Legacy 3.6R Limited
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1,157 Posts
Discussion Starter #6
Well just a quick update. I did put in the fuel cleaner but I haven't really driven it all that far with it in maybe 60 miles max. I reset the ECU just now. I let it sit overnight with the battery off, reconnected it (shut off alarm) started the car w/o touching the gas and let it idle till the fans kicked on. Turned the car off restarted it and drove around for a little bit. So far it seems fine. This was only one quick drive and it really wasn't sitting and getting cold yet so it's hard to say if this worked. After the ECU reset the car seems to pull a little stronger, it's been a while since I did one so who knows it may have worked. More later I'm keeping my fingers crossed.
 

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Scoobymods Guy
2010 Legacy 3.6R Limited
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1,157 Posts
Discussion Starter #7 (Edited)
Still there, it happens if the car is cold or been sitting ~45 min or so (still warm) but it only happens once then it runs just fine :(

not sure what to try next...
 

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Scoobymods Guy
2010 Legacy 3.6R Limited
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1,157 Posts
Discussion Starter #9
I did a double and triple check again on the vac lines. My vac guage is reading normal though (I have the performance guage pack) I was thinking the same at thing first.

I changed the oil today and was under there looking and poking around. I couldn't find anything funky. Still scratching my head hoping it will go away w/ the fuel cleaner . I got down to half a tank and put in more with the TecTron. I usually put the smaller bottle in the one good for up to 15 gal. This time I used the larger one good for up to 20 gal.

I'm thinking fuel system problems or maybe the TPS? Who know's...
 

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99 2.5 RS-T
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838 Posts
Check your plugs and wires. Then check the coil pack. Mine failed and it had similar hesitation symptoms prior to it crapping out.
 

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169 Posts
Could be the insulation on the wires breaking down. With some of the high humidity around the country the past few weeks it could be the innards getting just moist enough to retard a spark once or twice.
 

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Scoobymods Guy
2010 Legacy 3.6R Limited
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1,157 Posts
Discussion Starter #12
Update

Today the problem wasn't there, this is not to say it won't come back, but it did do the stumble pretty much every time before. Maybe the fuel cleaner helped. The only thing I did different was change the oil yesterday is all. I did poke and prod all the connections under the hood but they all seemed fine.

Gremlins I think. Hope it stays this way.

FWIW - My plugs are about 3 weeks or so old. I change them yearly. The wires are Magnecor in good shape. Good things to double check though. Not sure about the coil pack though that is a good possility. I wonder what they cost? Is there a better replacement?

I was going to get a ProECM but don't want to till I make sure this is sorted out.
 

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SAME PROBLEM IN 2002

I have an 02 2.5RS and I have the same stumble problem that you guys are talking about. After its been sitting a long time. Sometimes I pump the clutch a few times to see if it'll help. Any thing that works?
 
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