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Old 10-20-2009, 06:45 PM   #1
blusubaru
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Default Studder and shake at idle and through 1st gear (low rpm)

1998 Forester, 161,000 miles, automatic, stock 2.5L with air intake.

6k miles ago, it developed a severe hesitation through the low end of the power band until about 2.75-3k rpm. At oil change I replaced the fuel filter and plugs and wires (E3 Spark Plugs and Prestolite Proconnect wires). Everything ran great until recently.

Now car stutters and nearly stalls at idle. I have to hold rpm over 1k. Power through 1st gear is spotty, hesitation and stutters (misfire). At speed (40mph+), start to coast, and then getting back on throttle causes the car to cough and struggle to determine which gear it's supposed to be in. Tach will be all over the place as it decides between 3rd or 4th. This will continue until I let up and coast again for a few seconds then slowly get back on.

Check engine light will come on after this. Code indicates a misfire, according to dealership. They then told me that the ignition coil was bad. I foresaw this and replaced with a known working one prior to taking to them. They tell me that one is bad too. I ordered a new OEM coil and installed tonight, same thing. I know the O2 sensor is good, mileage hasn't dipped at all (still around 26mpg when it's drivable). Resetting the ECU fixes the problem for a few miles.

Am I looking at a bad plug wire? Maybe a vacuum leak? ECU flash? What do I do from here?

Also, I'm having lots of trouble finding a Subaru friendly indie shop in Indianapolis. Anyone know one? I'm tired of the BS at the dealerships.
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Old 10-20-2009, 06:54 PM   #2
yarrgh
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when's the last time you cleaned the MAF sensor?
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Old 10-20-2009, 07:03 PM   #3
blusubaru
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Probably never. That's what I meant by O2 sensor though. What's involved in cleaning it? Rubbing alcohol?
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Old 10-20-2009, 07:05 PM   #4
hybrid gti 2
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Pull the spark plug wires and look for oil. Common problem around your milage is leaking valve covers. My mom has a forester.
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Old 10-20-2009, 07:11 PM   #5
blusubaru
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Look for oil at the plugs end or the coil end (or both)? The plug end, as all know, are very difficult to get to without getting it on a lift. The plugs at the coil end are very clean.
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Old 10-20-2009, 07:14 PM   #6
hybrid gti 2
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Spark plug end

It's on top. No need for a lift.
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Old 10-20-2009, 07:23 PM   #7
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Did the dealer ohm the coil pack?
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Old 10-20-2009, 07:24 PM   #8
blusubaru
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Yes, and said it was arcing "all over the place" and looked bowed or bubbled as if it had been really hot. Brand new OEM has the exact same performance.
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Old 10-20-2009, 07:25 PM   #9
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Quote:
Originally Posted by hybrid gti 2 View Post
Spark plug end

It's on top. No need for a lift.
The plugs are on the bottom side of the engine and are very difficult to get to without the car being on a lift. The end of the plug wires that connect to the ignition coil are very clean. I have the MAF out of it and am getting ready to head to Autozone for MAF cleaner. Anything else I should pick up?
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Old 10-20-2009, 07:54 PM   #10
hybrid gti 2
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Oh I get it you have the dohc engine. Yea that might be a bit more work. This might not be your problem then. As the sohc often get oil in there.

I would check the gap on the plugs
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Old 10-20-2009, 08:13 PM   #11
Charlie-III
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I have a 98 DOHC, no issues getting the plug wires off. Removing the plugs means pulling some other stuff.

I don't know about those wires, I never use anything but OEM for Subaru plug wires.
I don't know about those plugs, I usually use (& recommend) NGK coppers for the NA's.

Pull the plug wires, look inside them, both ends. Also check the resistance. Also look for the plug end being oil soaked.
Pull the plugs, check them over.
Finish cleaning the MAF.

Do an ECU reset and then see what it's like over the next few days.
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Old 10-20-2009, 08:21 PM   #12
blusubaru
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Quote:
Originally Posted by Charlie-III View Post
I have a 98 DOHC, no issues getting the plug wires off. Removing the plugs means pulling some other stuff.
How in the world do you get to the back ones? Take the wheel off, turn the steering just so, then you need a long, skinny arm and small hands to even get in the vicinity. What's the trick?
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Old 10-20-2009, 08:22 PM   #13
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I have cleaned the MAF with the MAF cleaner made by CRC. Also remembered that I have another MAF from my '90 Legacy. Looks like they're compatible. I've cleaned both just in case the Forester's is the culprit. Letting them air dry over night and will try to get it going in the AM.
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Old 10-20-2009, 09:35 PM   #14
blusubaru
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MAF is not the culprit. Cleaned both, even swapped in the known working one and no change. Doesn't happen until the engine temp just slightly begins to move off of cold.
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Old 10-20-2009, 10:29 PM   #15
Charlie-III
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Quote:
Originally Posted by blusubaru View Post
How in the world do you get to the back ones? Take the wheel off, turn the steering just so, then you need a long, skinny arm and small hands to even get in the vicinity. What's the trick?
I have sorta long skinny arms, but not excessively so.

To do plugs, I dismount the washer resevoir (I let it run down in volumne so it won't spill) as well as the air filter box and part of the intake tract.
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Old 10-23-2009, 06:46 PM   #16
blusubaru
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Well, problem solved! The culprit was the spark plugs. Apparently the old girl doesn't like the E3's. Mechanic swapped in stock spark plugs and all is well again. Stay away from the aftermarket parts apparently on this first gen 2.5L.
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Old 10-24-2009, 05:07 AM   #17
Charlie-III
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Quote:
Originally Posted by blusubaru View Post
Well, problem solved! The culprit was the spark plugs. Apparently the old girl doesn't like the E3's. Mechanic swapped in stock spark plugs and all is well again. Stay away from the aftermarket parts apparently on this first gen 2.5L.
Subaru engines also seem to hate Bosch Platinum plugs & Bosch ignition wires.

They like Bosch water pumps (which are ~1/2 the cost of a dealer).
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