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Last week I replaced my plugs, fuel filter, air filter, and ran Seafoam through the intake. The first couple of days were great. The car was running smoother then ever, no hesitation, great acceleration, and I think it was quieter then it was before. Well, that's all over. Had a little hesitation this morning. I'm not sure what it could be. Plug gap? I went with the gap that was on the plugs I removed, about 0.050 inches...does that seem correct?

 

What else might it be? There's only about 30k on the plug wires, so I doubt it's them.

 

Oh, it's a 97 impreza, 2.2 and an auto tranny.

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Did you get NGK plugs? Subes seem to like these best.

 

I think BKR6E-11 are the ones you'd want. Plug gap is 1.1mm

 

I got NGKs. The ones with grove in copper flavor.

 

I just find it odd that the hesitation would return so soon.

 

Oh, and 1.1 mm is about 0.043 inches, so, I can't imagine that .007 inches would be a huge issue, but I suppose it could lead to fouling?

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Did you refuel during the period in question. With sky rocketing fuel prices here in Australia we also seem to have plummeting fuel quality, I was having similiar problems to you until on the advice of my repair shop I went off the discount regular fuel and went to premium unleaded. The difference was immediate. Its worth a tank to eliminate the possibility!

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Did you refuel during the period in question. With sky rocketing fuel prices here in Australia we also seem to have plummeting fuel quality, I was having similiar problems to you until on the advice of my repair shop I went off the discount regular fuel and went to premium unleaded. The difference was immediate. Its worth a tank to eliminate the possibility!

 

I just gased up the other day, but will try using higher octane on the next tank (as painful as that will be on my wallet). I do use the better brands, so I'm not concerned about actual fuel quality, but octane may do the trick. I suppose a can of octane booster would answer the question sooner.

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I just gased up the other day, but will try using higher octane on the next tank (as painful as that will be on my wallet). I do use the better brands, so I'm not concerned about actual fuel quality, but octane may do the trick. I suppose a can of octane booster would answer the question sooner.

According to my mechanic its not just the octane. He has found that engines running premium fuel are cleaner, from the fuel injectors, heads even the exhaust system and this is the real benefit. I'm trying it my Sube, so far insufficient k's to see if any real improvement in gas mileage, but the hesitation has gone. BTW someone advertises a add on which smooths the signal from the knock sensor and cures a lot of hesitation problems. Might be worth a look if the problem persists. Cheers

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You dont need the premium fuel.

Just use what the Mnau. specs require otherwise your wasting money.

 

As far as hesitation is concerned.

Yesterday on my VW club website one of our members who is the lead tech at a VW dealership issued a statement saying that they have been getting ALOT of VW in the shop with hesitation and fuel economy loss and just plain poor driveability!

They have chalked it up to the poor fuel we are getting at the pumps as the feds have been issueing fuel from the reserve tanks which have less additives thus we are getting alittle more carbon build up , quicker in our cars..

The fix......

They have fouind that when you fill up to add a GOOD fuel additive to the gas tank and do that for at least 2 tanks then every 3-5 tanks.

This has worked w/ great success.

 

Hope that helps.

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Fair enough, and at least you know its in the tank. Ive heard many stories of operators forgetting to turn pumps on when blending gasoline etc. Have you noticed a payback for your investment in the aditive? I've only done 600km since changing to premium, so far it appears the gas mileage has improved a little but its too early to tell. Cheers

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I had the same problems as you with hesitation, I added all the things you did, except I did not use seafoam. I drove for maybe 6 months and the hesitation got worse, I ended up fixing it by having the throttle body cleaned. Subaru's get gunked up after about 60k. Higher quality fuels and additives temporarily help because they burn better and hide the problem. Some things can cleam it with chemicals but wont remove everything. Physically cleaning it may help you.

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Sounds great but, I'm having trouble finding a solid procedure for cleaning the TB. In fact, many posts I've come across say do not clean the TB. Something to do with the black goo from the factory.

 

 

So, any good place to hunt the procedure on how to clean the TB in a 97 Impreza 2.2?

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Some do have some very strong views about cleaning TB's including Josh who really does know his stuff. Anyway I went ahead cleaned mine anyway, I bought new gaskets for the TB to manifold in case I broke the old one. I removed it, there are some pesky water hoses and other bits and cleaned with with brake cleaner because it does not leave a residue and also cleaned the IAC valve with brake cleaner according to Josh's recommendations. The cars driveability certainly improved. Whether it was due to the TB or IAC is debatable. I must say the TB was not nearly as badly gunked as I was used to seeing on my V8 Commodore. I also reset the TPS sensor after I reassembled everything and it was quite a bit out. So whether you clean it or not is your call. I'm inclined to think it they do not cleaning regularly on Subes.

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