# 1992 KA "bucking" proplem...



## JayLew (Sep 15, 2002)

Yes I searched, but, I found WAY to many conflicting stories.

Basically my car will not hold a steady RPM (while moving....it idles perfect however). Example: Im cruising at 2500 rpm with my foot lightly on the gas and then the car will start to jerk and hesitate for no reason.

One person said it is the MAF?

My friend said his TPS was causing his car to buck.

Another said that his timing chain tensioner was causing too much slack in his chain and causing the engine to surge erratically. <----My tensioner is bad by the way.

So basically if you guys have had this problem, what did you do to fix it?


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## dj42000_2000 (Oct 19, 2004)

i had the same problem, but I am probably in a different situation. when I first got the car, alot of the connections and sensors were bad, so I replaced my water temp sensor (the 2-wire one),the TPS, and the o2 sensor. my car had a blown head gasket and a leaky radiator, and every time the water level dipped a little, my car would buck. the engine management was very confused as to the actual water temp. so here's what I say: clean your MAF. take some air intake cleaner and spray the shit out of the wires inside it. clean your throttle plate(just because you're pretty much there already, and it won't hurt). Check your distributor, wires, plugs, and everything else you can. check all of the electrical connections you can find. check your vacuum and your fuel pressure regulator. check your fuel pressure. After a thorough inspection under the hood, unplug the negative terminal of your battery for approx. 10 minutes, then hook it back up.
Does this happen after the engine is warm, or while its still cold? did this start all of a sudden, or over time? is the car still driveable? if you want a walkthrough on any of the things I mentioned, let me know. I hope this helps some.
also, make sure to check all of your fluids.

truman
peace


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## JayLew (Sep 15, 2002)

dj42000_2000 said:


> Does this happen after the engine is warm, or while its still cold? did this start all of a sudden, or over time? is the car still driveable? if you want a walkthrough on any of the things I mentioned, let me know. I hope this helps some.
> also, make sure to check all of your fluids.
> 
> truman
> peace


It started very slowly, but, then a cold front hit this weekend and it got out of control.

Ive cleaned the throttle plate, changed the plugs, rotor, and cap, and the fuel filter is new <----I changed all of this before the problem happened.


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## calebxmartyr (Apr 9, 2004)

are you allowing your car to warm up all the way? cause i know mine drives bitchy as hell when its cold.


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## dj42000_2000 (Oct 19, 2004)

here's where i'd probably start. I'd check my thermostat and make sure its there and working(my car didn't have one due to previous owners). I'd also replace the engine management coolant temp sensor. make extra sure there is no air in the coolant system. the sensor shouldn't be more than $30. make sure it is the 2 wire. just as a side thought, how old are your hoses? they are like $10 a piece and its alot cheaper than a tow if one blows...
Since it idles fine, let it completely warm up and see if the problem goes away. if it does, my above course of action will remedy it. if the problem still exists, let us know.

truman
peace


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## JayLew (Sep 15, 2002)

dj42000_2000 said:


> here's where i'd probably start. I'd check my thermostat and make sure its there and working(my car didn't have one due to previous owners). I'd also replace the engine management coolant temp sensor. make extra sure there is no air in the coolant system. the sensor shouldn't be more than $30. make sure it is the 2 wire. just as a side thought, how old are your hoses? they are like $10 a piece and its alot cheaper than a tow if one blows...
> Since it idles fine, let it completely warm up and see if the problem goes away. if it does, my above course of action will remedy it. if the problem still exists, let us know.
> 
> truman
> peace


Thanks for the advice.

I think Im going to change all of the above regardelss of whether or not its the problem.

Right now though it looks as if my timing chain tensioner is to blame (causing slack and friction in/on the chain). 

Ill find out Friday for sure (my only day off to work on it). Ill let you know what the prob was.


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## dj42000_2000 (Oct 19, 2004)

Just for some info and reading:
you can probably check the chain tightness by removing the upper timing chain cover and valve cover. be wary after that point, replacing the timing chain is a fairly dedicated process (my head is off right now...). FYI: the tensioners are hydraulic. I am unsure as to the total milage of my engine (or car for that matter), but I'd guess around 180K on the engine, and everything related to my timing chain is in good condition. That said, they wouldn't have timing chain kits if it never needed replacing. The best price I found for pretty much everything but the seals was $250. best of luck with the troubleshooting/240-workday.

truman
peace


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## Prelude Guy (Jul 19, 2004)

How hard is it to check the TPS and coolant temp sensor??


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## JayLew (Sep 15, 2002)

Prelude Guy said:


> How hard is it to check the TPS and coolant temp sensor??


Its not hard to check a TPS, you just need a multi-checker, and the factory spec of the TPS.

And the coolant temp sensor is cheap enough to where you might as well just change it for the heck of it.


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## dj42000_2000 (Oct 19, 2004)

To answer your question, not too hard. the following material I have taken from the August '04 edition of Tomorrow's Technician, which my good friend Swich let me borrow/have. It has a full article on how to test nissan electronics.

For the coolant temp sensor, you'll have to tap into the wires going to it. there will be a power wire and a signal wire. as the temperature of the water increases, the voltage on the signal wire will decrease.

Engine Coolant Temp------Voltage------Resistance
14 F-----4.4V----9.2
68 F-----3.5V----2.5
122 F----2.2V----.84
194 F----1.0V----.25

For the TPS, you'll need a voltmeter or lab scope.
1. Start the engine and warm it to operating temp.
2. turn off ignition and wait at least 3 seconds.
3. turn on ignition switch.
4. check voltage between ECM terminal 23 and 25(ground).
With the accelerator fully released the voltage should be .35V to .65V. there should be a linear rise in voltage as the throttle is depressed. With the throttle wide open, the voltage should be at 4V.

The terminals mentioned are for OBDII cars I believe. I would just tap into the wires off of the throttle body.
hope that helps you out some.

truman
peace


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## Prelude Guy (Jul 19, 2004)

JayLew said:


> Its not hard to check a TPS, you just need a multi-checker, and the factory spec of the TPS.
> 
> And the coolant temp sensor is cheap enough to where you might as well just change it for the heck of it.


I see. Can you give me some direction here? I have a friend with an 89 240SX too. I was thinking about borrowing his TPS. Is it a part that can be easily taken off??

Also, where can I get a coolant temp. sensor?? Any pics of what it looks like??

Thanks,

Andy


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## JayLew (Sep 15, 2002)

Prelude Guy said:


> I see. Can you give me some direction here? I have a friend with an 89 240SX too. I was thinking about borrowing his TPS. Is it a part that can be easily taken off??


Dont take the TPS off of the throttle body, if you do youll have to recalibrate it, which can be a pain. 

The safest way to swap a TPS is to swap the entire throttle body..


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## dj42000_2000 (Oct 19, 2004)

the process of removing it can be quite a pain depending on the condition of the wires and how dirty everything is. anytime you're working after the air filter, getting crud or fluid into the engine is bad. basically to remove it you'll have to drop the intake side to the throttle body, the throttle body itself (which is held on by 4-6mm allen bolts), and all of the hoses/lines running to it. Be careful with the gasket unless you have another or are going to make one... the electrical connector is fairly large and is located about 4" away from the throttle body. installation is the reverse.
I'd make sure that you had the resources available to replace the throttle position sensor if it is bad, to keep from having to repeat the work. (aka at least find out if there is one in town...) sometimes i have problems getting parts same day, sometimes even next day. 
if your friends car is running properly, i would take your TPS and put it on his car. see if there is any difference. This can help eliminate possible issues from troubleshooting two problems. say your TPS and your coolant temp sensor are both misreading, you could pass by part of the answer and not know it b/c there was no instant change. misreading sensors can also occur when they are still reading, but not accurately.
when you swap any sensor, I reccommend disconnecting the battery for 10 minutes to reset the engine management. It will take a few minutes for everything to be properly set again after reaching operating temp.

JayLew-I've never had problems calibrating my TPS when I got one. It took the engine a few minutes of driving to relearn the fuel/spark maps and regain perfect idle, but no problems calibrating. How do problems like calibration occur and how would you fix it? just curious incase I have to one day...

truman
peace


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## Prelude Guy (Jul 19, 2004)

dj42000_2000 said:


> the process of removing it can be quite a pain depending on the condition of the wires and how dirty everything is. anytime you're working after the air filter, getting crud or fluid into the engine is bad. basically to remove it you'll have to drop the intake side to the throttle body, the throttle body itself (which is held on by 4-6mm allen bolts), and all of the hoses/lines running to it. Be careful with the gasket unless you have another or are going to make one... the electrical connector is fairly large and is located about 4" away from the throttle body. installation is the reverse.
> I'd make sure that you had the resources available to replace the throttle position sensor if it is bad, to keep from having to repeat the work. (aka at least find out if there is one in town...) sometimes i have problems getting parts same day, sometimes even next day.
> if your friends car is running properly, i would take your TPS and put it on his car. see if there is any difference. This can help eliminate possible issues from troubleshooting two problems. say your TPS and your coolant temp sensor are both misreading, you could pass by part of the answer and not know it b/c there was no instant change. misreading sensors can also occur when they are still reading, but not accurately.
> when you swap any sensor, I reccommend disconnecting the battery for 10 minutes to reset the engine management. It will take a few minutes for everything to be properly set again after reaching operating temp.
> ...


Thanks for the help, Truman. I have a question though. I thought that the KA24E and KA24E were different. i thought the CTS was MUCH easier to change compared to the KA24DE. The instructions you posted are for all motors or just the KA24DE??

Thanks,

Andy


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## JayLew (Sep 15, 2002)

dj42000_2000 said:


> How do problems like calibration occur and how would you fix it? just curious incase I have to one day...
> 
> truman
> peace


What I mean is that when you take the TPS off of the throttle body, and then put it on a new throttle body, it will no longer read to the factory spec. I just think using a multimeter and constantly rotating the TPS untill it reads the right voltage isnt worth the hassle.


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## dj42000_2000 (Oct 19, 2004)

as far as TB, I am speaking for the DE, as that is what I own. as far as the specs and such, I don't know any more than that is what Tomorrows technician had... I just replaced mine, so as to avoid any problems in the future... other than that, I don't know, but i can find out more if you need me to, or ask a few technicians i know. My friend has the E on his car and I could take a look at his and tell you more...
hope that helps.

truman
peace


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