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weird fuel cut during fast shifts

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eclipsegst3131

Banned Member
219
0
Jun 5, 2004
Manchester, New_Hampshire
ill bring it back to about a month ago. car was running good, but whatever. to my point. i was able to floor my car (16psi) and shift fast with no problems whatsoever. i brought my car to the dealership and got an act 2600 clutch and flywheel put in...i get it back and after the break in period of about 500 miles (let it be known i used a slowboy disc which requires NO break in, but i like to be safe) i go out and beat my car. shift fast into any gear whatsoever and when i drop the clutch and floor the gas it just stops and feels like it hits fuel cut hardcore. so i have to lift up and floor it again and its perfect. if i take like a second or a second and a half to shift it goes good too, no problems. i took my buddy for a ride in it and he said that maybe with the clamping power of the clutch its rocking my motor bad and that i should get new motor mounts with the prothane inserts (its a 93 and been in new hampshire for 10 years, so the motor mounts arent perfect condition whatsoever). any suggestions of what could be the problem? let me know ### im open for everything.


also btw--im running an open hks bov, but i was also running it before the clutch install...just in case it matters. i bought the recirc fitting tho, just waiting for it to get here.
 
got the recirc fitting today in the mail, already put on the car and did nothing to help it out at all. someone pleeaaseee help me haha :thumb:
 
pull the screen out of the lower smaller oval shaped opening in the bottom of your mass air flow sensor.....leave the big square one alone tho!!......that should lean it out a bit and stop the fuel cut.
 
ill try that out tomorrow afternoon when i get a chance...but im just not sure whether its that im hitting fuel cut or if its just flexing too much. i've hit fuel cut before and i know how it feels, and tho it feels the same when im shifting, it just doesnt sound like it at all :notgood:
 
Is it stuttering where the rpms don't go up even though you've got the pedal floored, or does it just fall flat on its face with no power?
 
it doesnt stutter at all, just flat out dies out when its shifted hard. i brought it to 6k, 5k, and 4k...let it sit and then shifted nice and smooth and i was able to floor it again into the next gear no problem....did it for a second time at those set rpm point and shifted fast as if i were racing or what not and as soon as i hit the gas to go in the next gear it would just cut out and then id have to lift up and get back into it. i even tried it again and when i got into the next gear only went down about half to 3 quarter throttle and it did it a little bit too... i think im gonna get some new motor mounts and fill em and im lookin at setting up an engine damper as well. everyone i seeem to talk to is 90% sure that my motor mounts are bad and the motor is rocking too much.
 
DSM007 said:
pull the screen out of the lower smaller oval shaped opening in the bottom of your mass air flow sensor.....leave the big square one alone tho!!......that should lean it out a bit and stop the fuel cut.

WTF Sorry... what??

eclipsegst3131 said:
shift fast into any gear whatsoever and when i drop the clutch and floor the gas it just stops and feels like it hits fuel cut hardcore. so i have to lift up and floor it again and its perfect. if i take like a second or a second and a half to shift it goes good too, no problems.

Are you sure that what you are feeling is fuel cut? It feels like someone taking a serious stab at the brakes. On the other hand, if you are simply losing power your knock sensor might be seeing some phantom knock from your new clutch combo, which as stated above, will tug your engine around. Best way to check is with a logger.
 
yeah like i said before i 'feels' like a fuel cut, but not 100% exactly like it. if its phantom knock, why is it cutting my car out only during the shifting?? and what if i turned my boost down?
 
I'd guess you're running a bit rich. There's a few things that make the car run more rich during a shift, and it's put you over the edge. It's enough to make the car misfire and hesitate. Like DSM007 is hinting at, try to lean it out somehow.
 
well unfortunately im working like crazy for the next few days, but on thursday im gonna hook up my boost leak tester to it and see what happens. i just dont think its something like the car running rich thats my only problem. because it never did this until i got the new clutch put in. and i can run 16psi no problem, it feels alot faster than before i had the car.
 
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