1st and 2nd gear bucking! help!!!

[240dreamer]

alright guys...i just bought a 95 240 SE, 5 speed and i have a problem. whenever i try to accelerate hard in first and sometimes in second, my car starts bucking violently back and forth...it's like the fuel is cutting out and back in really quick...it's almost comparable to hitting the rev limiter...when it does this it sometimes throws and engine code that has been diagnosed as the Mass Air-Flow Sensor by the previous owner. Most people i've talked to say it's probably a fuel delivery problem and not the MAF since it doesn't do it if i'm in another gear or accelerate normally. Any ideas what it is?!?! thanks.

-Adam

[quiksilvia]

see if u can get a mafs from a working s14 and plug it in and see if it still happens, do u have an intake? if this doesnt work, it could be a fuel system problem

[240dreamer]

i have the stock intake and today i replaced the fuel filter with the much larger 300zxTT filter and it still does it...there's almost no S14's around here so i don't think i can get one to see if it works...also, i listened to see if my fuel pump sounded irregular or if it sounded "normal" and it seemed to be functioning properly...

[quiksilvia]

check the ecu ur self

[240dreamer]

how?

[240dreamer]

the check engine light came on after i tested the fuel filter out but i don't know how to check the codes or even get the codes...i know i read something on it a while back but i don't remember.

[quiksilvia]

240sx.orggo there to faq and its there

[240_Keyy]

sounds kinda like gear lash, both of my S13's did it when I got them (but now only one does it thanks to an SR swap in the other)

[NISTECH]

air flow meter controls fuel delivery. start the car and let it idle. grab the air flow meter harness and move it around and see if the car starts to idle rough or even die. if so i would guess you have a faulty ground in your harness

[240dreamer]

ok, i found the FAQ but didn't have the ambition to screw with it last night...i just got back from work so i haven't tried anything yet...i'll try wiggling the MAF harness and see what it does, i'll let you guys know...also, i'll try to find out what code it's throwing...thanks. oh, and what's gear lash?

[240dreamer]

ok, wiggling the harness doesn't do anything at all, it just idles as normal...i just tried it.

[240SXd00d]

Clogged injectors? The problem with fuel injection is that when you let off the accelerator, the ECU over compensates for the loss of fuel pressure and the car "bucks." If the injectors are clogged, it would make the problem 10-fold worse.

Try running some fuel injector cleaner and/or 93 octane fuel (more detergents) through the car once over.

If that doesn't fix it, and the above mentioned suggestions failed, just take it to a dealer, as I can't think of anything else.

[240dreamer]

ok, i just did a diagnostic of the ECU and it gave me a code 12....which according to the FAQ, is a MAF sensor code. i suppose i could take off the intake and look at the sensor and see if it's bad or something. The previous owner told me that it sometimes gives a code 12 and he doesn't know why...i guess i could try some injector cleaner but it runs well so i don't know if that's it.

also, it only happens when i'm on the gas, not when i'm letting off. thanks guys for all your help so far...maybe i'll have to get a new MAF.

-Adam

[574-240sx]

I had the same problem in my civic and turned out to be bad spark plug wires. I know totally different cars. I would try using electrical connection cleaner and clean the connection. Nick

[NISTECH]

check your intake boot for a slit where it flexs between the rad and the throttle body. if its split ,when you accel it opens up and allows unmetered air into the throttle chamber and therefore reducing the amount of air mesured by the a/f meter. which would cut the fuel back cause it doesnt think it needs ittry lifting and pushing down on the boot while holding the throttle drum at about 2000 rpms.

[MojoMan]

Alot of times ppl think they need a new maf. If you take it out and use that electrical cleaner spray it may fix the problem. You can build up a lot of gunk and dirt on the element. The element has a tendancy to clean itself off but only to a certain extent. If the element cannot maintain the correct voltage to compensate for the increased airflow it will do this. Oh and check your plug gaps just in case and make sure they are not fouled out. If you need a better explaination go to www.howthingswork.com

[240dreamer]

thanks guys. i just had my spark plugs out yesterday in fact, making sure the most of my engine components are in working order and they checked out fine. Next thing i'll try is the intake boot where it's "ribbed" because i know rips or slits are common there. then if i can't fix it i'll find some electrical cleaner spray at the local store and clean it off. i think the plug wires are ok though. thanks for all the info. i'll let you know if anything works.