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Old 08-07-2009, 01:48 PM   #1
getek20
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Default Hesitation between 20mph and 40mph

I own a 2006 WRX Limited with 4EAT and 67k miles on the odometer. I have been experiencing hesitation between 20mph and 40mph. I haven't noticed any hesitation when downshifting. It only seems to be during upshifts. I even noticed that 0-60 times are consistently 5/10ths of a second slower in this car than my 2003 WRX with 4EAT which had the same amount of miles as I have now.
I've disconnected the battery and reset the ECU, but that didn't fix the problem. The dealer suggested a tune-up and a complete fuel system clean. Is this necessary? What could the potential problem be?
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Last edited by getek20; 08-07-2009 at 02:00 PM.
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Old 08-07-2009, 02:12 PM   #2
ShaneInHisRoom
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Not really enough info to diagnose, but you shoudl start with all fresh oil for motor, tranny, and diff.
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Old 08-07-2009, 02:22 PM   #3
getek20
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Originally Posted by ShaneInHisRoom View Post
Not really enough info to diagnose, but you shoudl start with all fresh oil for motor, tranny, and diff.
I don't have a whole lot of into to go by either because I just purchased this car 3 weeks ago. It has a clean title and is certified through Subaru. Only 1 previous owner. As far as I can tell he/she took good care of the car. No signs of modifcations or abuse.
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Old 08-07-2009, 02:23 PM   #4
djosbun
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How is fresh oil and differential fluid going to solve a hesitation issue? Where did you learn about cars, anyway?

Here are some REAL things to check: dirty air filter, spark plugs that need to be replaced, new fuel filter, clean your MAF sensor, etc. Stick with the basics. If you have no cel, then you are either having lack of air, lack of fuel, or weak spark.
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Old 08-07-2009, 02:28 PM   #5
getek20
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Originally Posted by djosbun View Post
How is fresh oil and differential fluid going to solve a hesitation issue? Where did you learn about cars, anyway?

Here are some REAL things to check: dirty air filter, spark plugs that need to be replaced, new fuel filter, clean your MAF sensor, etc. Stick with the basics. If you have no cel, then you are either having lack of air, lack of fuel, or weak spark.
I just changed out the air filter. The old one wasn't too dirty but I replaced it with a high flow air filter. It still hesitates even after replacing it. I'm thinking that the previous owner may not have bothered to do the 60k scheduled maintenance. The vehicle has 67k miles on it now. $300 some odd dollars to pay for the 60k maintenance on a 'new' car is a lot to fork out. However, I'd be willing to do so if it means fixing the hesitation problem.
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Old 08-07-2009, 04:22 PM   #6
ShaneInHisRoom
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Quote:
Originally Posted by djosbun View Post
How is fresh oil and differential fluid going to solve a hesitation issue? Where did you learn about cars, anyway?

Here are some REAL things to check: dirty air filter, spark plugs that need to be replaced, new fuel filter, clean your MAF sensor, etc. Stick with the basics. If you have no cel, then you are either having lack of air, lack of fuel, or weak spark.
Because it's easy to do and cost friendly. And especialyl with the car being 3 weeks old, a full fluid flush is a good idea anyway, even if it doesn't solve the problem.
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Old 08-07-2009, 05:15 PM   #7
kx02wr
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Dude you gotta pay to play. If you can't afford 300 bucks you prob shouldn't have a sports car. A high flow drop in filter is not going to make anything better, and they are frowned on as they usually don't filter as well as stock. Also if you do it yourself a 60k will be less than $100. Plugs, a fuel filter, and a pcv valve are all easy diy jobs which are the most important part of the 60k. Just cause the car is new to you doesn't mean it is a new car by any means.
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Old 08-07-2009, 05:25 PM   #8
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when you buy a used car with that many miles, you should have considered the fact that you will have to fork out extra money to give the car a tune-up. even if the used car doesnt have any problems, it would be good practice to just give the car the tune-up as soon as you own it.

how bad is the hesitation? do you have a boost gauge? is the psi spiking up and down as the car hesitates? does it hesitate between 20-40mph no matter what or does the amount of throttle matter too?

if its a hesitation problem with no CEL, i'm willing to bet its something with the intake system.. even if the filter is clean, there could be a leak somewhere, or spark plugs, fuel injector, fuel filter...

if you want to gamble the cheap way out, you can spend 7 dollars for fuel injector cleaner and run it in your gas tank... even if it doesn't solve the issue, it will only help your car. it got rid of my slight hesitation once and even increased my miles per tank by 30 miles.

it could be a vacuum/boost leak as well.. but its hard to tell without a boost gauge and without a leak test.

if you aren't car-savvy, i'd recommend you to take it to the subaru dealership, or any reputable subaru mechanic.

Last edited by vinxH; 08-07-2009 at 05:32 PM.
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Old 08-07-2009, 05:34 PM   #9
djosbun
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The fuel filter takes all of 3 minutes to replace, and can be had at the Subaru parts dealer for around $25, if I remember correctly. Do that first, since it's cheap and easy. If stuttering continues, then replace the plugs. Not hard to do, and cheap. Just have to pull the windshield washer resevior on the drivers side, and air intake box on the passenger side. You can purchase plugs cheap at Autozone (I recommend the NGK Iridium, and leave the pre-set gap at .030). Taking your time, you can swap all 4 plugs in less than 1.5 hours. Fuel system clean is unnecessary, unless the previous owner didn't put premium (high-octane) fuel in. Premiem fuel contains more 'cleaners' in it, so you would be wasting your money there.
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Old 08-07-2009, 08:40 PM   #10
vinxH
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Quote:
Originally Posted by djosbun View Post
Fuel system clean is unnecessary, unless the previous owner didn't put premium (high-octane) fuel in. Premiem fuel contains more 'cleaners' in it, so you would be wasting your money there.
premium fuel does not contain more cleaner than a dedicated fuel system cleaner. even if X fuel contains more cleaners than X fuel injector cleaner, you're still raising the concentration of cleaning agents in that gas tank than if you were running premium fuel by itself.

plus, how do you know if the previous owner put in good fuel or not? either way, it's an ok try if your car is hesitating. i use to barely break 230 miles per 13 gallons with some slight hesitation on moderate throttle, then ever since i tried a bottle of fuel injector cleaner, i'm hitting ~260-270+ consistently with nothing else changed, so i stand by fuel system cleaners for "used" cars. better way would be to do a real fuel system clean at a dealership, or by yourself if you have the right tools... but the OP doesn't sound too willing to spend some $$.

Last edited by vinxH; 08-07-2009 at 08:46 PM.
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Old 08-09-2009, 12:18 PM   #11
getek20
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I tried a few recommendations. Yesterday I used Techron concentrated fuel system cleaner. That didn't really do anything but it still might be too early to tell since it's been less than a day and I have driven less than 20 miles.
This morning I tried CRC MAF cleaner. I sprayed the sensor and let it sit for awhile before I hooked it back up. The car definitely seems to run a lot smoother now after a ~15 minute drive around the block. I noticed little to no hesitation on my ride.
However, after cleaning the MAF I noticed the little glass globe inside was still quite discolored. Even after using 40% of the can of cleaner the glass globe was still dark brown/black in color. It was so discolored that I could barely see the little coils inside of it. Should this be cause for concern?
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Old 08-09-2009, 01:27 PM   #12
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The "globe" is the intake air temp sensor. Don't worry so much about that, it's just a thermistor. The actual MAF sensor is the very thin wire way up inside the opening. That's what you need to spray (and don't touch it with anything or it may break).
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Old 08-28-2009, 03:27 PM   #13
getek20
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Update : I discovered the "hesitation" I was experiencing was actually the engine lugging because the RPMs were dropping too low. As I was driving around town in "D" the RPMs were quite low, especially when I was barely pressing the accelerator between 20 and 40 mph. Once the RPMs dropped below 1500 the engine would lug and the transmission would get confused as to what gear it should be in. This created a jerking motion and an abrupt downshift followed by a quick upshift. I discovered that driving around in "3" would keep the RPMs 500-1000 higher on the tachometer. This prevented the engine from lugging and also helped the vehicle to get up to speed easier. This also helped me to drop a half second off my 0-60 time. At least I'm happy to know that there isn't anything seriously wrong with my car.
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