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Old 07-26-2002, 01:51 AM   #1
imprezawd
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Default OK WHy did MY hesitation Problem RIse from 3-4 k to 4-5 k with cobb stage 1 cams??

OK well my cams were nice for a little. Then i had to fill up on some gas. I always have to start my damn car with the GAS pewdal all the way DOWN!! Thats the only way it will start.
SO I have the hesitation issue. BEFORE the cams I had a hesitation or flat spot from 3-4 k rpms, BUT when at WOT i had no symtoms. BUT on the new COBB cams mild I feel a huge flat spot between 4-5k and after 5 k its like a type R vtec I have some adjusting to do with the cams but the are lod but not to loud . I will have the tech adjust when the car is completly cold. WE did it last time with the motor around 130 degrees. ( pyrometer)

Can i get some comments and suggestions?? please


thanks
richie
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Old 07-26-2002, 04:29 AM   #2
Kostamojen
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Well, we kind of need to know what else you have done to your car
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Old 07-26-2002, 04:41 AM   #3
HndaTch627
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first of all you should NEVER have to hold the throttle wide open to start your car...sounds to me like your MAF is dead.

jeremy
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Old 07-26-2002, 09:43 AM   #4
Tim Smith
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I agree with the throttle thing. NEVER hold it down on a FI car. Turn the key to ON, wait a couple seconds, then start it. If it doesn't start, than you have something broken.

I am not sure of the MAF though. Seems like you would have a flat spot through the whole curve if the MAF died. Unless it was just burning rich to compensate. Than there wouldn't be a flat spot at all. Maybe just equally weak. But I could be wrong. Try unplugging the MAF and see if that helps. If it does than you should get it replaced. You can also pull just the sensor and look to see if the resister is burnt or popped like a fuse. (I might add that you don't want to touch it. ) I also think that if the MAF was dead if would throw a CEL.

I didn't know that you could adjust the cams in a 2.5. Or do you have the adj cam gears? I would help to know your other mods as well.

Good Luck. Let us know how the cams work.
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Old 07-26-2002, 11:35 AM   #5
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I think by adjustment, he is talking about valve lash. If you have noise from the lifters, that COULD be interpreted as knock and the ECU is retarding timing.

Do you have any sort of fuel or timing control?

When I started playing with my fuel mapping I noticed a bunch of strange holes where the stock fuel map is not smooth. I think this and the stock intake resonance were responsible for hesitation on stock cars.

I know a lot of people complained about over active knock activity on the early MAF based cars, so I think that is the problem.

J
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Old 07-26-2002, 12:32 PM   #6
imprezawd
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THE only way I can start my DAMN car is by HOLD THE PEDAL TO THE METAL. I know i shouldn't but All the tech at my dealershjip says not to but I HAVE TO . THE car will not start anyway else. I HAVE no fuel or timing changes. I have stock MAF and stock ECU. MY mAF is fine. IF my MAF was gone I would not be able to drivie it . I t drives awesome except the fact i have a really large fl;at spot around 4-5k YES adjustaing the valves i meant. Valve lash.

any onther suggestions??
I have every other bolt on but header and cat.
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Old 07-26-2002, 12:55 PM   #7
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I dont know anything about the WOT starting.

Have you done the knock sensor mod on your car? you might try it and see if you hesitation goes away. A lot of people have said this helps.

J
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Old 07-26-2002, 03:57 PM   #8
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IIRC you have a short arm intake right? maybe its something that never was an issue before but maybe the MAF is getting confused have you recently cleaned the filter, maybe to much oil.
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Old 07-26-2002, 04:07 PM   #9
Tim Smith
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IF my MAF was gone I would not be able to drivie it .[/b]

Not exactly true. On most vehicles (I admit I am not sure about the subby) if the ECU doesn't see a signal from the MAF it will follow a pres-et fuel map. One that burns rich to be safe. But if the MAF is giving a weird signal the ECU will still try to follow it, even if it is out of the measured range. I used to unplug the MAF and Temp sensor on my old car when I raced it because of the increase in gas flow it was more powerful. It just burned a ton more fuel. That and the cat would be glowing after an hour.

Someone tell me if I am wrong about the subby. But start the car let it idle then unplug the MAF and see if the flat spot goes away.

PS We are just trying to help you out. No need to yell.
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Old 07-26-2002, 06:31 PM   #10
Keith99RS
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imprezawd - Quit being such an ignoramus. The people here were just trying to help you out like you asked. For the record, the fact that you HAVE to push the gas pedal to the floor to start the car is an indication that something is amiss and needs to be looked at regardless of how you think the car is running. It may be the reason for the flat spot in the first place. If you are such an expert, why post here with your questions??
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Old 07-26-2002, 07:17 PM   #11
Kevin Thomas
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Default Fuel

Could be a fuel problem. Perhaps the car isn't getting enough fuel to start it so he has to floor the car to get the fuel to the cylinders.

As for the hesitation, it seems like something that is felt by many here. The hp/torque has always seemed to dip between 4k-5k rpm range on just about every subaru I've seen on the dyno (very few would be the exception). With the cams moving the torque up another 1k rpm, it just moved the 'problem' to another rpm range. People have been swearing on the SPG (Single Point Ground) mod removing that hp/torque drop and smoothing out the powerband. Can't hurt to try it out.
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Old 07-26-2002, 07:52 PM   #12
imprezawd
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thanks for all the suggestions. Keith 99 i have no idea what u are talking about. I am just telling you all what i think like you all tell me what u think. Please dont make this some annoying flame post. I need some damn help here thats all. Thanks for all the help. ONE thing though. THIS problem with the hesitation goes and comes as it pleases?? The techs at my work are clueless as well?? Why one day be all fine and the next be all weird?
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Old 07-26-2002, 08:17 PM   #13
Patrick Olsen
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First, a quick lesson in internet etiquette. When you use ALL CAPITALS, that is interpreted as yelling. When you say things like "THE only way I can start my DAMN car is by HOLD THE PEDAL TO THE METAL," and "I need some damn help here thats all," not only are you yelling, but you're adding in mild profanity for no discernible reason. That is interpreted as being rude. With those little etiquette rules explained, I think Keith99RS' comments were entirely in line.

Moving on....

I, too, am having a hesitation problem after installing Cobb Street cams. http://forums.nasioc.com/forums/show...ght=hesitation . In my case it happens at a lower RPM, and wasn't present at all before installing the Cobb stuff. I haven't been able to figure out why it's happening, but the ECU is definitely pulling timing. I've confirmed that with a PocketLogger OBDII scanner/datalogger on my Palm Pilot.

Have you tried resetting the ECU to see if it makes the car any happier? What happens if you try to start the car without the gas pedal on the floor?

Pat Olsen
'97 Legacy 2.5GT sedan
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Old 07-26-2002, 09:17 PM   #14
Kevin Thomas
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Lightbulb Disecting the problem

Quote:
Originally posted by Patrick Olsen
I haven't been able to figure out why it's happening, but the ECU is definitely pulling timing. I've confirmed that with a PocketLogger OBDII scanner/datalogger on my Palm Pilot.

Pat Olsen
'97 Legacy 2.5GT sedan
In what situations would the ECU pull timing? I'll be the first to admit that I don't know a whole lot about cars but from the 'little' that I know the ECU pulls timing because it detects knock. It does not mean that the car is pinging or knocking but that the knock sensor detects what it thinks is knock and so the ECU retards timing.

Just based on what you said Pat, I'd say that the car(s) are knocking or for some reason the ECU is recieving a false knock signal (Over-sensitive knock sensor). Just a thought!
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Old 07-27-2002, 01:13 AM   #15
imprezawd
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PAt thanks for the help. If i try to start the car after i fill it up it will just crank and crank and crank but not completely turn over and start up. ??

I have read that their is a MAF recall for my MY 99 impreza rs and has been fixing the hesitation problem?

I wonder if this problem will go away like it use to when the rgular cams are in?? I need to get my valves adjusted. They are pretty loud. But not as loud as they where when first installed.
COBB recommenbds and better adjusting and 10w 30 instead of 5w or 0 w 30 oil...

Man this suck My car would be very fast for a N/A if i didnt have that damn hesitation !!

thanks
RIchie
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Old 07-27-2002, 04:30 AM   #16
HndaTch627
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first of all i was only trying to help

second of all your valves WILL NEVER be lose enough to create knock

third of all holding the pedal to the floor is a clear flood mode...that's what happens when you have an injector leaking down.

fourth i'm done helping, peace
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Old 07-27-2002, 09:49 AM   #17
Patrick Olsen
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Default Re: Disecting the problem

Quote:
Originally posted by Kevin Thomas
Just based on what you said Pat, I'd say that the car(s) are knocking or for some reason the ECU is recieving a false knock signal (Over-sensitive knock sensor). Just a thought!
I agree with you, Kevin, but I really don't have any way to prove that's the problem. A new knock sensor is $88 - not too bad, but I'd rather not spend that money on a wild goose chase. The cheaper option is to do the "knock sensor mod", which is just a matter of putting a plastic oil drain plug washer under the knock sensor. That might solve my problem, but I have no idea how much doing that really affects the knock sensor - would I effectively be completely disabling it? What if there really is knock, and I deaden the sensor's response so much that it doesn't pick it up? Obviously that's not a good thing. At some point I probably will break down and buy the new knock sensor to see if that helps at all. I'm also wondering about my MAF sensor, although my S-AFC shows good, smooth flow even when the car is hesitating, so I don't think that's the problem.

Quote:
Originally posted by imprezawd
I have read that their is a MAF recall for my MY 99 impreza rs and has been fixing the hesitation problem?
Yes, there is a MAF recall, talk to your dealer to see if your car is part of it. I honestly don't know what it was intended to fix, as my car isn't affected by the recall so I haven't really paid any attention.

Pat
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Old 07-27-2002, 05:52 PM   #18
Kevin Thomas
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Default Re: Re: Disecting the problem

Quote:
Originally posted by Patrick Olsen

I agree with you, Kevin, but I really don't have any way to prove that's the problem.
Pat
Pat,

Do just one or two test runs. Get a washer and place it under the knock sensor and see if timing continues to be pulled.

BTW: Could you tell me where you got that PocketLogger OBDII scanner/datalogger for your Palm Pilot? Thanks!
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Old 07-27-2002, 11:15 PM   #19
imprezawd
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Ok well went to parts department and got the NEW MAF After the recall and installed it and WWWWWOOOOOOWWWWWW
NEW car. Back to normal. Awesome ride. I will see on my next fill up if i will need to hold the pedall down. THE new MAF peice was a little different than the original. thanks for all your help. I saw a couple of GUYS in the RS Club were saying the maf recall is the first thing i should do, so i did

Thanks for all your help i will see if my hesitation creeps its way on back
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Old 07-28-2002, 08:31 PM   #20
HndaTch627
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god forbid...a technician might actaully know something
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Old 07-29-2002, 12:21 AM   #21
AzNStiImpreza
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Default i have rallispec

my rallispec fast road cams are very nice. at 4k rpm the car decides to fly. my idle is incredibly low tho, 200rpm, it feels like it is dying. that does hesitate my acceleration a little bit, unless i lauch it.
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Old 07-29-2002, 11:53 PM   #22
imprezawd
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Damn It
Its back :monkey: :monkey: :monkey:
Drove my car to my work (stohlmans) and took the OBD computer thingy they have and went driving on this graph mod to see my ignition, fuel, a/f, ans etc. I saw some graphs moving one way and some the other. It was hards to drive my car hard and see what the hell the graphs were doing. I know for sure it was droping timming or ignition on the graph when my hesitation arrives @ 4k-5k. After the 3rd run no more hesitation I should of runned it again when the hesitation FLAT spot stopped and looked at the graph to see If i saw the same speratic graph moves? but i didnt. OH and the check engine light always comes on for the VENT controlled sylenoid valve. I already have replaced it twice. It is not the problem every time i replace it the same check engine light will come on. I have a problem and the techs look puzzeled and really dont need a confusing job especially with my after market which is not the dramatic. The are to busy Oh well. My car runs fine

And my fill up i tried not to use the gas pedal just let it crank for a liitle then turn it off and back on the purge the sytem again and again and again and then finally the bitccch started BUT she smeels like crap and runs like **** for about 20 yards. ??

i need a new motor ..EJ20 sounds good with a stand alone ECU NO MORE crazy SOA ecu's
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Old 08-04-2002, 01:33 AM   #23
pdximpreza
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Try resetting the ECU. If the problem was cured with a new MAF sensor, although temporarily, it may just be a noisy signal. I would also check all of the wires to the ECU, too much exposed metal from the wire to the ECU will pick up noise. And since there is a strong Signal from the ignition system it could give false signals.

This is all speculation since I dont know exactly how the ECU works and all. But your best approach is to get it on a dyno and see what OBDII tells ya, since you think you saw one of the graphs wacking out at 4-5K, you may want to see which graph it is.
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Old 08-06-2002, 01:32 AM   #24
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SPG
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