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Old 07-31-2006, 08:54 PM   #1
SoDmFst
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Default Car studders at 5 psi .

I just put on the APS turbo inlet on my car and now when I hit at least 5 psi, it starts to studder , or hesitate to get gas. we had to take out the injector rails, so I think it might be the injectors might be off by a hair but I dont know. I work at a subaru dealership and my master tech and I have yet to find out what has happend. I would Like to see what all of you have to say about this. Thanks .
Seth
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Old 07-31-2006, 09:51 PM   #2
Hagwag02
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***I cleaned my MAF sensor yesterday for the first time.***

I ran an APS CAI for a year and was unsatisfied. Then I reinstalled the stock airbox and ran a Green panel filter.

With my UTEC and tuning, the stock threshhold for open-closed loop fueling of 7 psi (???) was lowered and is now between 3 & 4 psi.

I have had a problem with a stutter right around that point between open and closed loop. I changed to one step colder plugs, and I can't honestly say that it helped with that particular problem, but otherwise was a MUCH needed improvement.

I got rid of the Green filter and decided to try one of the new Amsoil filters.

But I didn't clean the MAF sensor for several weeks.

I cleaned it yesterday with some electrical contact cleaner. Drove it to work this morning.......... smooth as butter. I can still sense the point at which the fueling changes, probably because I know exactly at what point it is supposed to happen.

So, having had a similar situation, I would suggest that unless you have an FMIC, go back to the stock airbox and get a panel filter that doesn't need to use oil as part of its filtering media. Many times these CAIs will throw off the air metering readings being sent to your ECM, as I read many times but was too headstrong to believe it until I was forced to deal with it myself.

In any case, try cleaning the MAF sensor with some electrical contact cleaner or MAF cleaner if you can find it.

Just my .02 worth. Good luck.

Edit: I misread "inlet" and substituted "intake". I'd still check your MAF sensor and its readings.

Last edited by Hagwag02; 07-31-2006 at 09:56 PM.
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Old 07-31-2006, 11:39 PM   #3
SoDmFst
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thanks for your hep but I cleaned it a couple of weeks ago when I got my car tuned. I think it has something to do with my fuel delivery. I am going to tae the injectors out and try putting them in again, maybe they were in crooked or something. Thanks for your help though.
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Old 08-01-2006, 09:48 PM   #4
turbo'98L
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it could be that your fuel injectors arent giving enough gas to the cylinders. with an upgraded turbo you might need to get bigger fuel injectors, or it might be a tuning problem. when i turned up the boost on my car i got a hesitationwhenever i got up to about 5 psi. id try tuning first, do you have a system so that you can tune your car by yourself, if you dont then this could get expensive. or you can get bigget injectors off of ebay(cheap) you should shoot for like 600+ cc injectors (stock STi run 550cc's). i could be wrong but it sounds like then same thing that my car did and new injectors and a little tuning worked out just fine.

and for tuning emanage is a very easy way to tune you fuel system but not a lot of shops know how to use it.
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Old 08-01-2006, 09:53 PM   #5
hondaeater69
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is the MAF in backwards?
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Old 08-03-2006, 11:08 AM   #6
hulkSTi
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the injectors can be in crooked? i have a stumble problem around 2500 rpms. are there any other symptoms for the injector being crooked? i pulled out my MAF sensor today and the side facing the air filter is just covered in this black sludge looking stuff. cant see the bulb at all, its completely covered in it on the filter side of it. on the side away from the filter, its fine.

i went to the auto store to find MAF cleaner but cant find it anywhere. the electrical cleaner will work?

i hope this is the cause of my stumble problem.
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Old 08-03-2006, 08:36 PM   #7
Hagwag02
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Quote:
Originally Posted by hulkSTi

i went to the auto store to find MAF cleaner but cant find it anywhere. the electrical cleaner will work?

i hope this is the cause of my stumble problem.
Just make sure that it reads something to the effect "dries completely with no residue".

Electrical contact cleaner fits the bill. Also read somewhere that non-chlorinated brake cleaner is suitable, too.
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Old 08-03-2006, 08:51 PM   #8
hulkSTi
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Quote:
Originally Posted by Hagwag02
Just make sure that it reads something to the effect "dries completely with no residue".

Electrical contact cleaner fits the bill. Also read somewhere that non-chlorinated brake cleaner is suitable, too.

i found maf cleaner. i spoke with a local pep boys auto shop and they carry it. will pick some up tomorrow.
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Old 08-05-2006, 09:41 PM   #9
SoDmFst
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Thank you all for your help. I found the problem !! my fuel rail on the drivers side somehow got bent up just a little for it to shoot feul out of it when I reved it up. its now fixed and runs great. thanks again

Seth
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Old 08-06-2006, 03:08 PM   #10
Hagwag02
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Good to hear. I'll have to file that one.
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