insane bucking?

[thewhiteone]

alright so i was driving today, jot got my car put back together from doing a bunch of maitanance and fixes from the old owner.

Including new 725cc injectors, new intake, dyno tune, belt replacement, and a conservative tune at about 15 psi for now.

Around 4000 rpm, in all gears, if im on the accelerator too hard, the car starts to buck, for lack of a better time.

after doing my research, im thinking that i am in fact hitting fuel cut when the turbo is hitting. however, with a walboro 255 and 725cc injectors with a professional fuel tune, this shouldnt be happening should it?

any ideas on possible problems or solutions are very much appreciated.

thanks in advance

 

[PieEyedPiper]

Ask the guys who tuned your car, first. What are you tuning with?

 

[dented_coffee]

Sounds like a bad TPS. Mine was doing the same thing at WOT but it would hold 12psi solid and go till 5k and start to buck and I got black smoke out of my exhaust for a second.

I have yet to buy a different TPS to replace mine but I have tested my old one on the ohms meter and tested a good working TPS from a friends car and the studdereing issue was solved.

 

[BleedBlak]

Any engine codes?? Mine sorta did this..more of a stumble/buck when started building boost and getting on it...but my car would throw a code..."random multi cylinder misfire" my car would enter limp mode and wouldnt accelerate anymore and my egt would start to rise rather than speed...i would have to pull over, erase the code and everything woulkd kick back on and be fine... since then ive got it tuned and never had the issue again...id definately take it back to who tuned it...you spent money to have your car tuned and running efficeintly and you didnt get your moneys worth...

 

[rlacasse1]

Have you performed a Boost Leak Test yet?

You should.

 

[98spydereugene]

Could be a fuel pressure problem???dirty clogged injectors..or a problem with spark causing actual misfire..just throwing those out there

 

[98GSXtacy]

Have you performed a Boost Leak Test yet?

You should.

This.

And also, if you are able to, try to swap out your tps with a known working unit to see if that resolves it. It is not umcommon for a tps to wear out in a certain position and cause drivability issues at one certain rpm area but drive totally fine everywhere else in the rpm band. And if it is the tps, do a boost leak test anyways just for peace of mind.

 

[thewhiteone]

small boost leak from exhaust manifold, almost unnoticeable. The tune is done with apexi neo AFC. Injectors are brand new so it sounds like it the TPS might be the solution.

Its only under full throttle that it really gets bad. Its there still at higher speeds, but if i back off it goes away.

 

[rlacasse1]

And exhaust manifold isn't a boost leak.

Have you done a boost leak test on the intake side?

 

[Imback]

The afc can't compensate for those injectors.

 

[Boomdeeze]

The afc can't compensate for those injectors.

^^^ AFC is know to be good up to 650's so those injectors are too big to control with the AFC.

 

[thewhiteone]

I guess some new tuning equipment is in my future.

now i just have to figure out link or AEM.

 

[98spydereugene]

Dsmlink would be all you'd need, easy to use and learn, and much cheaper...It would do anything you need that's for sure.

 

[XLR8]

Did someone tune it for free? I would hope if they returned it to you like that you would not have paid them. DSMLINK is definitely the way to go. Good luck, sounds like you are on the right track.

 

[counti41]

well if u have a 98 or 99 dsm then u can flash the ecu its a bit cheaper but you would have to do the tuning yourself or get someone to tune it for you, tuning yourself isnt too hard though. im using ceddy mods and its really good.

 

[scott90gsx420]

Your running way to rich.. Without a chip or evo mas those injectors cannot be compensated for with just a safc. fuel cut feels like your in boost then the hand of god just stops you dead for a second then lets go and don't ask me how i know this. i know its freaking violent and i wanted to puke every time i ever felt it. And if you dont have a AFPR to go with that 255 your running even richer. If you don't have one get it and if so then id say drop the fuel presser a tad bit to help remove a bit more fuel. ultimately those are just to big get a smaller set of injectors or link, evo mas works but thats just a band aid.

 

[counti41]

Your running way to rich.. Without a chip or evo mas those injectors cannot be compensated for with just a safc. fuel cut feels like your in boost then the hand of god just stops you dead for a second then lets go and don't ask me how i know this. i know its freaking violent and i wanted to puke every time i ever felt it. And if you dont have a AFPR to go with that 255 your running even richer. If you don't have one get it and if so then id say drop the fuel presser a tad bit to help remove a bit more fuel. ultimately those are just to big get a smaller set of injectors or link, evo mas works but thats just a band aid.

damn dude its not that bad, i used an afc for a while with my denso 720cc and after a bit of tweaking no fuel cut but i was running pig rich at wot though and no fuel cut unless i was over 25psi on my e316g