Please help, My car is dying....

[emperor_lunchbox]

Whenever I lift off the throttle, the car bucks and falls flat on its face.This is just basic driving, not abusing the motor at all. This problem has gotten progressively worse, at first I thought it might have been bad gas, then the transmission, and then the plugs....Now I am at a loss. I need this motor to last til I get my spare built. What do you guys think?

[S13 240SX]

kinda need a little bit more info to try to help you out... hrmmm how does your car idle?

[Ni2s4s0aSnX]

Bad or loose sensor maybe, or sensor wires.

[emperor_lunchbox]

my idle is rough. it bounces between 5 and 700 rpms. I also get a hint of valve tap.I thought it might be my catalytic converter, I had a ford probe that had a clogged CAT and I gutted it and it fixed the problem.But this time the car bogs when I lift off the gas. I cant hold the car at one speed either. If I am going 45 it will buck, but when I accelerate to 50 it stops. If I hold it af 50 it will buck so on and so forth...any ideas to what could cause this. I also think it could be my throttle cable. Its sticks. When it bogs if feels like someone is tapping the brake while I am still holding the speed. its very annoying and starting to concern me.

[S13 240SX]

well man still can't firuge it out for you... only thing I can fix of, is run the ecu for codes, spary some wd-40 on the throttle cables to get them not to stick, and run some sea-foam in the break booster line, and some sea-foam in the oil.. if you run the sea-foam you gotta make sure you run the car while adding the sea-foam in, run the car for 5 to 10 minutes, and then shut the car off, and right away you must change your oil aftter you are done running the sea-foam though... those are the only tips i got for ya man.

[Ni2s4s0aSnX]

Yup, throttle cable sticking could cause that problem.

[Meantime]

It sounds like you are running too rich. Your most likely culprits are one (or more) of the following sensors gone bad, listed in order of likelihood:

1) Coolant temp sensor2) O2 sensor3) MAF sensor

In my experience it is usually 1) that causes the problem and since it's $25 at the dealer and takes about 10 minutes to replace, check that out first. I've had that sensor go bad on both my KA and my SR and it caused all sorts of bogging issues both times. It didn't throw a code either time, even when the sensor was bent/cracked from corrosion.

O2 sensor is also cheap and easy to replace. It doesn't sound like a MAF sensor issue, usually that causes a wacky all-over-the place kind of idle if something is amiss. Check 1) and 2) before you go any further.

[emperor_lunchbox]

well, there is a new problem. I have noticed that the when I am at idle, the rpms rise and drop very quickliy, like I am tapping on the gas. The whole car shakes, it feels like its going to stall, but it doesnt.Has anyone ever had this happen before. Could bad plugs cause this?

[AmoebAssassin]

My car had the same problem as yours and it was the coolant temp sensor.

[emperor_lunchbox]

I will be replacing the coolant temp sensor in the next few days. I have heard from a few people that that could be the source of the problem, So that will be the first thing I replace. I will post back when that doesn't work, and yes, I am a glass half empty kinda guy.

[NateDogg]

Why don't you test it instead of potentially wasting money. THe only way to troubleshoot is to find the 'trouble' and then 'shoot' it. Can you dig it?

[emperor_lunchbox]

I can dig, How do you test the coolant temp sensor?

[s13drft89]

Sounds like what had happened to my car, my problem was my oring in my injector, (number 3),also could be another one, the bottome oring would usually tear, which had then sent to much fuel, and have a misfire, and cause the motor to run on only 3 pistons, as well as the idle low, and the car shaking, start up the car, go into the engine bay, now unplug an injector 1 by 1, leave it off for about a good 5-7 seconds, now if the the idle drops then the oring is fine, now if the idle is the same as before, then mostly the oring is no good, also check the grommets(hold the injectors in line, rubber circle piece) but first try the unplug injector trick.-Ricky

[emperor_lunchbox]

how much do injector O-rings run?If they aren't too expensive (I can't imagine why they would be, but who knows...) I would just replace them.Does anyone know the part number?

[s13drft89]

Orings doest cast a lot but there are pretty pricy at the dealership, thats where the only place i can find it at, non my local automotive (kragen.autozone, etcc) have any. Just call in the parts department, and ask them how much for the 91-98 240sx orings, if you are going to change them out, make sure to get the ones you need, or are you just going to get all of them? remember before putting in the injecter lub it up with some grease, only the oring, not the whole injecter, if you dont have any grease, do the trick that nissanfanatic taught me which is to dip them in motor oil. Then put them on the injector and put them in. tighten the caps, and your good to go. hope this helps.-Ricky

[RotaryKnight]

well, there is a new problem. I have noticed that the when I am at idle, the rpms rise and drop very quickliy, like I am tapping on the gas. The whole car shakes, it feels like its going to stall, but it doesnt.Has anyone ever had this happen before. Could bad plugs cause this?

From the look of it, it sounds like you have a dead cylinder.Check all 4 cylinders for spark, fuel, and compression.

[emperor_lunchbox]

well I got the car back from the shop today after 7 days. My mechanic (former) says its the IACV valve and I just don't think that could cause all of these problems. I dont think he even looked at it. Altho, he did do something to it because it wouldn't start. Oh well, I am building a new motor. Hopefully I can find all the parts soon and get some people who can help me install it.

[Dattebayo]

Idle issuse are pretty common with KA motors.

If its your "IACV" it could be one of two valves, the "AAC/IACV" on the firewall side of the intake plenum or the "air regulator" under the intake runners (hard to get to...).

If the idle fluctuates like you say it does, then it souds like a viable diagnosis from your mechanic. The AAC/IACV is pretty easy to replace if you have a 10mm ratcheting box wrench like this one:

Dont forget to get the old gasket crap off, too!

[JNM240]

Before changing out anymore parts, at least check the vacuum hoses to the IAC valve. Your car is 15 years old, and that means the rubber hoses are 15 years old as well. If they are cracked and leaking air, instant bad IAC valve diagnosis. Also check the electrical connector that plugs into the IAC valve, as well as the electrical connector that plugs into the coolant temp sensor. If they are green and corroded, clip some decent ones off a junkyard donor (doesnt even have to be a 240, any Nissan plug will work) and solder some new ones in.

[emperor_lunchbox]

is there a way to buy new ones, is there a kit or does anyone know of the part numbers. I have been to junk yards around here several times, they are bone dry. They never have anything close to what I am looking for. I would like to try and replace all of the vacuum lines for my new motor (if I keep going on with the project).

[S13Coupe]

Just curious. Did you or your mechanic ever get a fuel pressure reading?

[emperor_lunchbox]

I dont think so. I am not too sure what he did. I dropped it off on a Tues. and I picked it up the following Tues. and it didn't want to start, had an oil leak and wouldn't shift into second. But I got that fixed. I think I need a nissan surgeon. My car is really sick.