Thread: Weird bucking/hesitation/bogging in 1st gear only

im having a weird problem that im really having difficulty solving, first my problem was a partial throttle acceleration studder, i tried setting the tps to .38 closed and 4.03wot, helped but still didnt solve it, so i was also having bad cold start studder and hesitation/flooding causing the hesitation. So i remembered i hadnt switched my jdm coolant sensor to my new usdm one when i swapped the motor, i didnt think that had much affect, but i switched it and set my tps voltage to .45 closed 4.16 wot, partial throttle hesitation gone. Nice and smooth,

Now my main problem, This only occurs in 1st gear. My setup is as follows.

Calum basic ECU 370's 4bar, Z32 maf in blow through setup. Now here is the thing, ever other gear is perfect, 2nd just burns the tires like crazy, 3rd gear spins the tires till 70-75, 4th and 5th are smooth, all gears accelerate smooth with no hesitation, no bogging, no misfire, no detonation. Im running 12psi of boost but the initial spike is around 19psi. T25 setup, i know i know poor t25, but ive been running this setup for a while, this just started to occur a couple weeks ago.

No matter what i do in 1st gear when i punch it, it starts to want to just burn the tires then it just cuts out, to the point where it almost feels as though the engine shut off then kicks back on bucking and misfiring through 1st but bam hit second and the tires go up in smoke it will pound off the rev limiter with no problems and go hard. Its only f'n first gear. What the Hell.......Im almost thinking maybe a maf problem. im gonna redo the ground for it and also run a grounding wire from the battery to the intake manifold where i have all the other grounds including my MAF ground. But its weird as hell. I cant lauch the car from a stop because once load is put on the motor and it starts to make boost it cuts out, bucks, hesitates to the point it feels like the motor shuts off, then it kicks back on and goes being the car is still in gear. Any ideas. Weird problems popping up lately, Oh and ive been running the Calum Ecu for a while with no problems, this just started a couple weeks ago out of the blue. I dont have any boost leaks so dont ask, im smarter than that, all couplers are good. Unless my MAF has just all of a sudden busted a huge boost leak somewhere going up through the sensor. but i doubt it because i would think it would affect all the gears not just one.

my P.O.S car is doing the same on 1st now.. at 12 psi.. when i punch it it sorta wants to cut out and misses.. like pftftftft sound... it was only doing it once.. but hasn't done it since... i bet if i smash it again it will do it... im might be needing the car for work, so i might be thinkng of putting it back to stock but i dont want to.. we'll see..... laterz..

Jr...

Does it happen when you are just driving around too? From a roll?

Or at a certain RPM?

Do you get any backfiring that you have noticed?

So you are blow through? Did you check that MAF for leaks at any time? Did you plug that little hole that goes to the circuit board? I have had two that leak really bad you might want to check that out.

My checklist would be first check for boost leak (hate to say it but it really sounds like the culprit have you checked for leaks in the hoses on the intake manifold or just the boost tubes?), second ignition problem the easy stuff plugs/wires. distributor, third maybe sensors they would be going into limp mode if they were bad.

well i just got done switching my intercooler piping up a little bit, havent taken it for a drive yet but i will let you know, heres the thing with my setup, the bov was really close to the maf, plus the bov adapter pipe i had slid all the way into the maf to make clearance for the pipe to go down into the fender. Well i think that was not allowing the air to spread enough going through the maf being the flange was almost all the way up to the hotwire. So we will see, plus i moved the bov down into the fender well so its a couple feet away from the maf and the maf has a nice section of pipe on both ends. Either that the maf possibly might be leaking from the circuit board area like most with the z32 mafs have. If this doesnt cure it i will go ahead and probably just seal that maf up with jbweld like everyone else used to be sure. If that doesnt work im thinking its a maf problem.

I will keep it updated for future reference

Good thinking the MAFS are very temperamental

yeah its still doing it, guess the next step is to jbweld the top of the maf, oh well. guess i will start with that, i really dont see what else it could be, everything else checks out good.

your out

Well guys i finally figured it out what was the cause to the stupid bucking/cutting out/hesitation/falling on its face topend

besides the poor t25 having had about enough of my abuse i finally figured out the problem,

I went out last night to do a couple runs on my slicks on the newer G-tech meter but couldnt even make a pass because it was cutting out and just wouldnt go through 1st and 2nd gear. Went and swapped mafs because thats what i thought might be the cause and no same thing, so then i gave it a shot and turned my fuel pressure back down to stock 3 bar, and whalla, i could feel it right away just normally driving it that the car was running soo much smoother, better idle, better reving, no backfiring, no poping no sputtering no nothing, did 3 passes and holy hell it moves, i still could only muster a 2.1 60' because i was just spinning the crap out of the slicks but i didnt have the time to do any more runs to try and feather it out without spinning off the line

Granted i had my buddy in the car and it was 91 deg out with about 60% humidity. My only clean run was a 12.6@114mph 2.1 60'ft

The car flat out flies, my topend is back, it doesnt fall on its face soo bad after 6k anymore, the car put a whole new smile back on my face, ive been battling with the stupid problem for about 2 months now. What i dont get is my Calum basic is setup for 4bar fuel pressure 370's and a Z32 maf, i dont know if its a problem with my adjustable fpr spiking fuel way high under boost or what, i dont have a guage inside the car to tell. but i know for dang sure that it runs 100X better at 3 bar, its rediculous how fast this car pulls, i did a 10mph roll on the slicks just to see how well they would grip and how fast the car would go, holy crap, i went from 10mph to 60mph in about 3 seconds flat, little to no wheel spin on the slicks in 1st from a roll just went and right after i punched it i was at redline quick shift and bam 60 was up just like that. Rediculous

Just thought i would let you guys know what solved the problem, so if any of you guys are having a similar problem like that just give a little tuning a shot, mess around with the fuel pressure.

Is it possible your fuel pump was hitting the wall at 4 bar?

What pump / FPR were you using, (just for the record)?

Do you run a fat wire and a relay to your pump?

I am asking because it seems as if the $600 Weldon pump and a well made fuel pump relay is in my future, if I expect to run at 5 bar using the AEM MAP sensor, as my turbo is larger than what you are running.

How much pump do you need to run at a boost spike, using -6an braided fuel lines and an Aeromotive FPR? Do you gents think the Aeromotive A1000 will meet demand, for a 4-5 bar injection system, using 750-900cc injectors?

Or is the Weldon 1015, or 1025 more likely to be required to meet demand, under max boost? (God willing the internals hold up for 80% of max recommended boost).

My physics knowledge and fluid dynamics calculator for correctly feeding the beast is a bit rusty, at best. (though I am brushing up on classes for both schools of thought).

There must be at least one super mathematician in the group who can define the process for defining the size and ratio of fuel pressure / pump flow requirements, for a modified turbocharged engine, so we don't hit the wall and detonate the engine or run lean.

Anyone got a slide rule chart so we can make a better guess at the minimum FPR requirements, under boost / per injector? (Yes I realize injector size and flow rate make all the difference, and this is why I am asking for any professional limits the OG's may have found out, for us; the hard way).

This info would make a great sticky, based upon injector size and expected boost, for the most common turbines and head configurations. (But then who would blow an engine, right?)

its not the fuel pump, i have a walbro 255, so yeah, it could be the regulator, im running a nismo universal afpr. its always worked fine before, then just slowly started doing this worse and worse, so im guessing maybe the regulator was crapping out jumping up fuel pressure but i had no way of knowing because i dont have a fuel pressure guage in the car to see while im driving.

Oh well im just glad its fixed.