partial throttle sputter

[Xero]

my 93 nissan 240sx has been having this huck-up lately.

when I'm driving down the road, the car runs good, under acceleration it's smooth, deceleration is smooth, but the switch between them, is horrible.

if I find that spot in the throttle where it switches, I can get it to buck and stutter all over the place. Also, I've noticed lately that the engine is dropping revs real quick. I used to be able to shift smoothly, but with the same shifting habits, I don't hit the throttle soon enough to catch the dropping revs, so I kinda do the bucking thing going into gear.

also, sometimes it'll idle very poorly. If I pop the hood and shake the clump of wires that has the 2 temp senors, TPS, and MAF all near the throttle body, sometimes I can get it to drop idle suddenly, but then it comes back and idles perfect at 750rpm.

my tailpipe is also very black, so it's running super rich.

I don't know if it's caused by one thing, or my whole car is falling apart, but I'm kidna tired of hunting down electrical gremlins on my own.

I have checked the TPS, voltage is perfect. I have checked the IAV before, it works, dunno if it works all of the time, I know sometimes the ground on it can be bad, so that might be something for me to try.

and on a completely unrelated note, my auto-seatblet system is acting up. It reads that the passenger seat isn't connected, but it is. I've pulled on it to make sure it wouldn't just pop-out in an accident, but the light stays on for a while, then turns off after a period of time. sometimes I'll be driving and I'll hear a click from over there, and the light will coem on and the bell will ding, but then after that same amount of time, it'll turn off.

thanks much for any help you can give, you give a great service to this community.

--Justin

[Xero]

also, I have done all my regular maintenance, plug wires, fuel filter, I've run toluene through the fuel before, cap/rotor, O2 sensor.

I might try the O2 sensor again, though, but that wouldn't 'cause just a sputter at partial throttle, that'd be all over the rev range.

[BurntClutch]

Check the big coupler hose that connects the intake duct and the throttle body. It might be ripped. Though a ripped coupler would make it run lean, its worth checking. Mine is ripped and I had weird problems like that until I duct-taped it. I think it also would be disturbed when you tug on the TPS harness like you were saying.

Have you had it in really heavy rain since this started? Mine would stall out coming to a stop in heavy rain. I guess the filter would get a little wet and more unmetered air would come in through the rip.

[NISTECH]

check the connector for the 2 wire coolant temp for corrosion and female pin for loose fit on the sensor terminals.

[Xero]

I replaced that about 4 months ago, but I did clean the connectors today, I even bent them upwards a little so they'd make a better connection.

It helped a little, but the sputter is still there.

[Xero]

I believe I fixed it. I was going through checking things, cleaning electrical connections, and I decided I'd check the O2 sensor, swap it ou tfor my spare I had. I pulled it off and it seems some how my O2 sensor had exploded. I had ceramic sticking out of the holes, and it was rattling. So I swapped in my spare and it doesn't sputter anymore. yay!!

[Xero]

k, I lied. gremlins are bak, and they brought friends.

I still get the part throttle sputter like before, though not as bad. 100% is awesome. 50% is rough atsome points in the rpm band. getting down around 5% it's really bad, very rough.

a second problem that has arose could be causing all or part of the first one.

I've noticed that when I turn the car on, it sits at 1500rpm. It will drop down, but it used to idle cold at 1100.

going hand in hand with the most recent problem, when I'm coming down a hill on compression, it will occasionally surge, like I was stabbing the throttle.

I really think it's a mix between the IAV and the TPS.

any suggestions with the new unfo?

thanks much

--Justin

[s13sr20chris]

did you replace the sensor harness when you did the coolant temp sensor? also it does sound like you have a tps issue even if the tps checks out good.

[NateDogg]

Check the resistance of the TPS throughout its sweep and make sure it climbs with the increase in throttle angle. SHould be 1k ohm at rest and ~10k ohm wide open.

[portisroads]

does it have a hard start? if so does it do it worse when the engine is hot or cold? usually surge is coused by a lean condition. is the surge down hills still at half throttle or when your completely of the throttle? have you checked the spark plugs to see if they are bad?

[andox]

I think I have the same problem. Please anybody and everybody help me.

Car Details: 1990 240sx (ka24e)

Confuseing.. manufactured 89 but it says 90 i dont know what to say..

So far my car is stock except for the following:

Air filter: I took off the box stuck on a air filter on the maf with the sensor just push in there.

Exhaust Tip:Took it off a friend's celica when he crashed and added it on to my stock pipeing.

Sympton:If i give it partial throttle after 3k rpm (ocassionaly) my car'll sputter. It will sputter at 4k rpm for sure. I can feel something I think passing through my exhaust.. kind of like 3 big air bubbles. or 3 quick back fires..

If i cruise at 4k ocassionaly it'll continue to sputter.

When it sputters, it can be "strong" enough to bother my traction and weight balance. Can't turn very fast up in the canyons.

Someone please help.Thank you

[NISTECH]

this air filter thing you got goin on sounds a bit suspect, But not sure I completely comprehend what your trying to say you did.Better discription or pics will definitly help.

[andox]

for the air filter..

i just took off the stock box and stuck on a filter that my friend gave me.But for my model there's some type of sensor that conects to the box. The 91 and up doesn't have this sensor.

=====D <~ pretend that's my stock intake manifold.. and the "D" is the air filter..

I unscrewed the sensor from my box and just stuffed it in through the bottom of the airfilter where it meets the intake manifold.

===D ^ |

When i get my hands on a digital camera i'll take a picture.

[NISTECH]

Ok I know what you did. Is it an oiled filter? if oil gets on the MAF it can hose it up.

[andox]

I dont think it's oiled.. im a lil confused.

[NISTECH]

I stated I knew what you meant,I know what you did you added a cold air intake.

If the filter is a K&N style filter it is usually oiled, If over oiled ,the oil will get on the hot iwre of the airflow meter and damage it.

[NismoRacer34]

Ok, I'm bringing up an old thread but better that than make a new one, right?I'm having the exact symptoms as the op. I recently had the engine out to install a t25 turbo. At first it was too rich to start and I figured out my z32 maf was missing one of the two grounds so I replaced the terminal and spliced it into the other ground wire. Now I'm getting the same sputter/misfire the op was having. I would pm him but he hasn't been active in four years . It seems to be running very rich at idle.Setup:T25370cc injZ32 mafEnthalpy ecuWalbro 255Emissions delete

things done so far:Checked voltage of tps- .5 closed to 4.2 wot smooth in betweenchecked maf volt- .5 off 1.1 idleNew o2 sensorNo vacuum leaks found

Also, just in case it helps, I tried setting idle and it will not go under 900 rpm even with the screw in iacv all the way in. Like I said, no vacuum leaks found though.

Please help