Im feeling hesitation under both part throttle and full throttle acceleration right between 2000-2500 rpm. This isn't anything abrupt and I've only noticed it 2 days ago. There have been no recent mods (month or so) that I can think of being the cause. The hesitation isn't bucking or rough, its more of a lack of power/acceleration almost like lag before the car pick up a bit around 3k rpm.

Any suggestions? Car has 69k miles btw and 6mt. Also injectors haven't been changed/cleaned yet nor has the fuel tank sock/filter, possible causes ?

 

i had similar type of problem, i cleand my MAF sensor and it went away

 

List your mods! If you have test pipes and are getting a cell light then that is what causing what your feeling. I had the same thing until i got a tune.

 

I doubt it's injectors just cause it happens at certain rpm's....I would start with the MAF and clean it like glenn280 said. but who knows....

 

thanks for the tips, engine mods are very limited and only include z-tube, spacer, and a wire tuck (engine harness wires weren't cut so i don't think that was it).

I'll go ahead and clean the MAF tomorrow and report back, I've also ordered new spark plugs since I haven't done the 60k service yet and maybe those are getting a bit fouled up by now.

 

Well, I cleaned the maf sensor and replaced the air filter while at it, but no real difference and the car is still not pulling. New spark plugs are ordered and on their way and if that makes no difference I'll start looking into the fuel system.

 

Try checking the fuel filter, if its clogged it can cause hesitation.

 

That is incorrect. The bank 1/2 #2 o2 sensors DO NOT play any part with the ECU in determining the car's a/f ratio, nor do they tie into the ECU in a way that will effect performance whatsoever.

All they do is read catalyst levels and determine if your running dirty, and if so, they activate CEL...thats it. that CEL has no effect on performance. Now if is was your #1 sensors, thats different.

+1

 

Do these cars even have fuel filters in the engine bay? I thought they were in gas tank

 

Well, I changed the spark plugs and although it improved the general behavior and pull of the car, the hesitation is still there. Its a small improvement but clearly not the root of the problem. Also I have noticed that the problem starts appearing only after the car is very well warmed up so after 20 to 30 min of driving.

From my understanding the only fuel filter that is present in the car is a "sock" type filter attached to the pump in the fuel tank. This will be the next thing I tackle.

Also is it reasonable to guess that my fuel pump might be tacking a dump? I vaguely recall stumbling into some thread a while back where someone claimed that the stock fuel pumps die pretty easily. Is this correct or am i imagining things ?

 

the problem is progressively becoming worse and today it became apparent that the hesitation appears basically from 2000-redline. The car just falls on its face when I step on it. It even bucks around 2200-2600 when just suddenly stepped on.

Im now considering the fuel damper being a possible issue with the diaphragm not opening properly and causing a lean condition. Did anyone ever encounter this, suggestions, guesses? Any input would be greatly appreciated.

And btw i'm really starting to see the value of data logging :/

 

For future reference the problem turned out to be a leak between the plenum spacer somewhere. After tightening down some of the bolts the problem disappeared, I can't believe I didn't check this before...but oh well.

 

I've noticed my Z is doing this, just started this week. I can feel the hesitation between 2300 to 3000 and then it really picks back up. No mods on the car at all...time to investigate.

 

i would check your engine cover and intake piping.. i noticed my engine cover bolts and intake pipe was not tight. once i torqued it down and reconnected my intake piping.. hesitation was gone.

 

I forgot to update the thread. It turned out to be the knock sensor so I replaced the it with a new one and I remade the knock harness with some spare wiring and high temp expandable braided tubing. That did the trick

 

Having the same issue, can you elaborate more on the knock sensor (couldn't find it in the service manual) it location or how you even determined it to be faulty?

 

i know that, i know exactly what you said. But he doesnt have tp so it doesnt matter. Mine did the same thing he had at those rpms. To prove a point when i would reset the ecu, for 50miles i could gun it or rev up to 4k smoothly. after 50miles (always) cell light turned on. Then the hesitation started. Once i got my tune never have experienced that again. also, if you did a lil searching im not that only one with that problem.

 

ok . . is this the same for the HR ? 2nd set of o2s (cat o2s) are not used for A/F . . and just for CEL light . . . . . assuming OP has DE and not HR . . . if he has a HR . . then im a dumbasss

 

might be air/fuel ratio. ever thought bout getting a reflash???

 

I was going to replace the knock sensor and harness cause i was throwing a P0327 code, read something about the throttle body too. Being lazy I just swapped the throttle body and that hesitation is gone for sure, but now of course with swapping the throttle body i'm getting the high idle (confirmed no leaks) and after multiple resets of everything the CEL still comes back on, idles high. Have to find out what code its throwing now, but you fix one thing only to deal with something else. Digging thru the forums, seems its common but no for sure fix.