Ka24de Drivability Issue

[NismoTypeX]

I own a 93 240sx, and im struggling to find out whats Making my 240 seem like it bucks after shifting, and bucks when I let off the throttle then reapply it. Feels like I have bad throttle response and a slight bogging problem.- I have tried nearly everything. New crank/cam sensor, new injectors, new Maf, new CTS, used M/T Tps sensor w/ a good reading on a ohm meter, 2.5' Cat back w/ Twin-loop muffler, Removed that Emission box next to exhaust Manifold w/ vacuum lines plugged, Pollished Aluminum intake with k/n cone filter. Tried Ngk Iridium IX's, then put standard V-powers to see if a difference. No Change in problem. New clutch, Walborro 255lph fuel pump with new fuel filter. MAF sensor (re-grounded to Distributer Adjusting bolt)-Things I know are not good... on the IAC there is a Sensor on there that the black plasic electrical peice actually can turn 360' around on its metal base that screws into the valve, could that make it not function? -other problem burns about a qt of oil a month.

now since my IACV is not new but cleaned, could that affect drivabillity, I know it effects my Idle, I will sometimes runn 800-1000rpm with vibrations then it will dipp down to like 600-700rpm and sometimes it'll bounce down between 400-500 and want to cut off (heavy shaking) then comes back up fine and will do this about once every min of Idleing.

please leave some Tips, Ive tried almost everything-Thanks

[rotorimp]

Sounds kinda like you may have dirty/bad injector--it would cause all of those symptoms--If you can afford to have your car down for a week or two send the injectors to be cleaned and balanced--worst that can happen is you get better gas mileage and more power.

Your IAC can also lead to some of these --what is the valve dutycycle at?

[rogoman]

- check for a sticking EGR valve- make sure ignition timing is correct- check for a major vacuum leak- check fuel pressure with a temporary gauge

[NismoTypeX]

I did do some test on it and changed some settings on it-Plugged off the EGR Vacuum (at both the diaphram and hose) revved it up still problem even when I open the egr with my finger. Hooked it back up and then felt the egr valve moveing as it reved up, but when the rev starts to choke a little the egr moves up and down. also took a vacuum test tool to it, worked fine.-adjusted Tps by hearing when the car sounded to smoothest or when the engine din't have as much of a shake to it(also new motor mounts).-while adjusting the tps I played with the timing (advanceing and retarding timing), to see when it was the smoothest, it still had a studder to it,-fuel pressure test 40psi, pressure increases as throttle is opened. New fuel pressure regulator also-tried injector cleaner and seafoam through the throttlebody/ and Iacv-vacuum test came up with anwhere from 17 then sometimes after the throttle comes down it may go up to like 23 then after throttle snapped it would drop, then might stay at 17 steadiy till throttle is moved

[rogoman]

The vacuum is on the low side. With the motor fully warmed up, the reading at idle should be 18 - 20 InHg. At 3,000 RPM, it should be 21 InHg.

If readings are under 18 InHg, check the intake manifold nuts to make sure they are tight; check the intake plenum bellows at the throttle valve and at the MAF for cracks or loose clamps. A low and steady reading can also be caused by late ignition timing, late valve timing, and low compression.

[NismoTypeX]

Thanks for the info, but I think I may have found the Culprit, The backside of the engine (Between firewall) there are 2 Ported vacuum switches to I unplugged one of them.... it changed idle (Guessing that it workes) i plugged it back in, it works. So moving to the next one I gently move the wireharness and notice the wires to the connector are separated from the switch. So i need to solder the wires back into the connector , or rigg it with a junkyard one.

BTW does anyone know where a IntakeAirTemp sensor is on a 93 Basic model Wew lightest of em all (its not in the aircleaner box, w/ no wires to intake box)

Thanks, I'll give ya'll a heads up if it works

[180fan]

the air temp sensor is at the airbox...

[NismoTypeX]

Do base models have a Air temp sensor?

Ported Vacuum switch didn't fix problem but made it a little better (I guess)Rewired it with a new pigtail w/ soldered connections. I guess this is a common problem, looked at junkyard ones and they all broke off or cut off, or could my vacuum switch just stop working, any spec on resistance or anything? Car ran real smooth with no vibrations but still studderd after shifting, till car warmed up, then once again it seems as though it boggs, and I can drive and shift in WOT and car is ridiculously slow but doesn't buck after shift, no power till Higher RPMs. Anyone got the specs for the TPS voltage? I need to set everything to stock settings, if I can, then move on from there.I'm about over this POSAny suggestions?