Im getting down to the last straw with my car, the stutter has gotten much worse and it does it from the time i start the car until i shut it down. From 1k rpms to exactly 4k rpms, the car will buck and hesitate, and just not accelerate worth a crap. Right after 4k rpms, the car takes off as normal. I dont have any check engine lights either. Ive replaced MOST of the stuff on my motor. There are a few sensors i havent touched..ie crank angle, cam angle, and maybe one more. Ive replaced the coil, wires, plugs, headgasket, seals, you name it. I dont think its the clutch anymore because of the 4k rpms thing..does anyone have a clue as to what it could be?

sounds like a fuel related issue to me. Fuel pump, fuel pressure regulator, fuel injectors, fuel filter are most componets of the fuel system, so be sure all are in good shape and working properly. Be sure you dont have a big vacuum leak somewhere either.

ive replaced everything but the fuel injectors. Wouldnt i get a code for running too lean tho?

i forgot to add that my a/f guage is reading correctly and it doesnt say that im running lean at all

bump

Just making sure, have you checked the wells for oil lately. As mine fill up the stutter I get becomes progressively worse, I never got it to stutter above 3.5k but once I cleared that oil out it went away, coming back now though. Just something for you to check out. Later and good luck
Brent

Get a mecahanic's stethoscope and listen to each of the injectors at idle. They should all make a clicking noise, indicating their proper operation. Put the stethoscope on the body of the injector obviously and listen for the noise.

I had a bad #3 injector, and it was a MAJOR PITA finding out what the problem was. I replaced EVERYTHING as well. The engine made a horrible misfire sound from idle to abour 4000 rpm's. When I heard, or rather couldn't hear any clicking on that injector, I was elated!

Give it a check! (I'm sure during my stage 1 and 2 days with the HRC kit running my fuel pressures to over 100psi quickened the demise of that injector, as well!)

My brother has had similar problems with his GSX and the culprit in his case was the spark plug gap was too large. The only other things that I can think of that would cause that are:
1. Bad ECU (doubt thats the case)
2. Bad cam angle or crank angle sensors
3. Your knock sensor is over torqued (should be torqued to 7 ft/lbs)
4. Your cam timing is off
5. Fuel injection issues as stated by XtremeRS

Could you reply back with exactly what you have done and what exact modifications you have? I think that will help to at least narrow down the possibilities of whats causing that some.

Ok, i'll try and list everything ive replaced..if i forget something, you'll see why
coil
wires
plugs
battery
intake
filter
removed egr system
iac
tps
cleaned tb and intake manny
milled head
valve job
head gasket
timing belt
all main seals
front o2
cleared cat
new muffler
gas tank
fuel filter
fuel pump
fuel pressure regulator
There might be a few more minor things, but thats all i can come up with now. I havent replaced the cam angle or crank angle sensors, but i just might do it to be safe. Im going to try and check the injectors as soon as i get a stethescope. Im running out of things to check and fix, there has to be someone out there that can determine whats wrong with my car. As you can see ive spent lots of money on the car and ive been raped by satan three times trying to figure this out. Can anyone help??
The only mods done to the car..aem short ram, cleared cat, new muffler, and a bored tb.

I suppose another possiblilty is one or two of your rockers have broken or something..It only takes a few minutes to pull the vavle cover and verify that all your valvetrain is in order. Also check the timing marks too, just to be sure thats dead on. I suggest a compression test too, just for kicks. It could be one of your sensors, but thats not as likely.. I always start with the basics: good comression, good spark, and proper fuel flow.

Don't rule out the crank and cam angle sensors, they are the sensors that control ignition timing and spark. If it's fluctuating back and forth it could mess up driveability. Fuel is also a posibility check out those injectors.

Check for vacuum leaks, even something like a TB not tight enough can cause a leak (saw as one of your mods). Also could check for exhaust leaks... it's possible to cause weird things.



15.9 @ 86.7mph

Injen CAI, 55mm TB, P&P Intake, Crower Cams, Hooker Header, ERT/Catco Cat, GS-T Muffler, AFX UDP, Crane Ign Amp, S-AFC

i just checked over the car, and i had oil in the first cylinder well. I clean it out and im going to fire up the car and see how it runs. As for the rockers being broken, how would i check for this? I know for a fact that when i redid the head and all i didnt prime the lifters..could this cause a problem? Someone suggested a burnt valve as well, but again, the head was reworked about three months ago, and i had the same problem before. im leaning towards the bad injector/cam angle/crank angle sensors. Where is the crank angle sensor located? The injectors are the last thing that id have to replace in order to have a brand new fuel system, but what im thinking is..4k rpms is when the motor kicks into its fuel loop, and if the injectors were bad, it would still stutter even at the higher rpms. am i right? This is probably the simplest thing going wrong and its taking forever to figure out. Any more input?

quick update. After cleaning the cam angle sensor and clearing cylinder well 1 of all the oil, i took the car for a spin and romped it. The car drove normal! The hesitation was gone..for the moment and it accelerated normally. A few of the bolts on the valve cover are stripped and im going to retap them tonight or tomorrow so i can torque the cover down. If this is the problem im going to be very happy.