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Power FC Datalog of bucking problem

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Old 05-25-04 | 08:23 PM
  #26  
reza's Avatar
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Re: Have you.....?

Mine starts when PFC is installed, never noticed the problem with stock ECU.

Originally posted by Beast From The East
Put the stock ecu back in and see if you can duplicate this issue on this car? If you can, then it's a mechanical/electrical issue with some other component. If not, then you're probably right to point the finger at the pfc. Have you also tried a known good pfc from another car, loaded this map and tried it in another car (or swapped the pfcs between cars?).

I took a peek at your settings and don't see anything out of the ordinary - I run similar settings in that area and don't have any of these issues. However, you don't seem to have a wideband - it would be nice if you got one hooked up to see what the true afr is when all this is going on. Under decell you should be in free air, but it's hard to tell what is going on since it appears all you have is the stock o2 sensor. However, when you initially decel and get the bucking, your regular o2 seems to indicate a temp rich condition before jumping way up indicating free air conditions. I wonder if you have an injector that isn't shutting off on decel correctly?

Maybe the crank angle sensor is misbehaving? As previously suggested, have you just checked the timing with while reving the car in neutral?

Lots of troubleshooting left (unless you've already done this and just have not provided all the sordid details). I'm certain it's frustrating.

Bizarre.

Beast
Old 05-25-04 | 08:31 PM
  #27  
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Seems to be specific to Hyperion's setup

Reza, this seems to be specific to the car/pfc that Hyperion has, not a general PFC issue. This is the first time I've heard of anyone having this kind of problem, so I wouldn't expect you to have it. Although, something is definitely not right if you set your fuel cut recovery to 4K rpm. You definitely don't have to do that if everything is properly working with the pfc and fuel/ignition system.

Any updates, Hyperion?

Beast
Old 05-26-04 | 12:43 AM
  #28  
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Originally posted by reza
Delayed TPS value would mean that the dashpot works correctly. You know it slows down the closing of butterfly.
the TPSV plot shows a decay consistent with a dashpot. the plotted inj dc and the table TPSV and inj dc values show a 'hold at fixed value', then zero, which a dashpot does not do. also weird that vacuum didn't change more during the test.
Old 05-26-04 | 02:26 AM
  #29  
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I do have the exact problem that hyperion has. It is very annoying at autocross where you letgo, then get back on throtle it would jerk....

That is why I am following this thread as well.
So far setting it to 4000rpm is doing good for me.

Would it has anything to do with removal of airpump and emission related stuff?
I know in the stock airpump/emission, the ACV is letting some air into the LIM. Maybe because the airpump not there to give air in, it cause the car to jerk when the butterfly close. Basically choked the engine out of air.... what do you guys think?

Last edited by reza; 05-26-04 at 02:29 AM.
Old 05-26-04 | 09:21 AM
  #30  
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there is an air bypass valve at the TB that opens during decel, using a solenoind valve for signal air. the airpump never pumps air into the intake manifold.
Old 05-26-04 | 10:00 AM
  #31  
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Lack of airpump not the issue

I have a t04s with street port and no pump and don't have this issue at all. I'd suspect the solenoid that Kevin is talking about might be the culprit for you and for Hyperion. My idle is smooth, no bucking on decel, car is scary as hell fast.

Hyperion, any updates?
Old 05-26-04 | 10:57 AM
  #32  
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Which solenoid whout this be? Is it ISC? Idle Speed Control?
I don't remember seeing Decel Solenoid in the control diagram or the manual...

The airpump does feed some air thru the ACV!

Last edited by reza; 05-26-04 at 11:00 AM.
Old 05-26-04 | 04:59 PM
  #33  
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I think it is the ISC.

The ACV allows air to enter the cat converter, or the exh ports in the housings. No pumped air to LIM or UIM or any intake point. Pumped air only goes to exhaust. will wager 1 cup of coffee on this one
Old 05-26-04 | 05:42 PM
  #34  
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Kevin you should wager more than a cup of coffee ....

I have a bucking problem too ... only mine is because my ring gear is worn out.
Old 05-27-04 | 05:15 PM
  #35  
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Ring Gear ???? Wait...is this on the Differential?
I know I have problem with the differential. it is too lose. It has about 1/4 turn freeplay...
Old 05-28-04 | 12:08 AM
  #36  
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yes ring gear in the diff .... the worse your gear gets the worse the bucking on/off throttle gets.
Old 05-28-04 | 01:00 AM
  #37  
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ahhhhhhhhhh.....okay...that is the ring/pinion thing right?
Dang..they are expensive to replace over $400...
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