pretty lousy powerband,

[rsmithdrift]

Let me put it this way, this guy that owns a tunning shop and has done countless SR20 and RB25 swaps on S13 and S14's actually told me my stock KA had 11.5/1 compression .......Do'h

Anyways, yeah, go to autozone and get a bosch universal O2 sensor, (they'll tell you which one for your car) it's like $15 bucks and easy as pie to change out (unless yours has welded it'self in like in my old Z )

and if yours was bad (check the 240.org faq on ECU diagnosis to figure out how to check) it may drastically improve your MPG and help out your bottom end/partial throttle torque.

Edit: and your gas tank is a 13 gal, but you can force 15.8 into it. Or aleast...into mine.

If I get 100miles per 1/4 tank it means I'm getting ~ 28mpg.

[lbrowne]

If I let the car go really empty I can get 50+ litres into the tank, thats going to first click off of pump, and then goin till it clicks again (which is usually right after) It seems that the capaacity is around 60 litres - if theres any other Canadian folks in here....

[ka24dave]

i havent actually had the patience to track my mpg exactly yet..although i need to. and i bought a bosch o2 sensor yesterday for $18. it normally would be 30+ but i got the kind that you cut and splice in yourself, saves money and i still get a premium sensor

[lbrowne]

so is there 1 or 2 I replace on my 90 s13?

Splicing it in with the old connector, don't you have to solder it?

[ka24dave]

dunno, i only need the one on the exh. manifold itself. looks like it unscrews, and yea i plan on soldering it on the old wire with the connector end, for a good connection. the replacement o2 sensor i bought also came with a lil shrink tube, that you heat with a heat gun ( or if your primitive like me, use a lighter at a distance ) that goes over your splicing to shield the wire and cover it snugly.

[rsmithdrift]

There is just one, it's on the exhaust manifold, and you have to have a special tool to get it out. (it's like $2 for the tool at any auto part store, just tell them what your doing and they'll know) because of where it's at.

It's going to be really really tight and a bear to get loose, but once it breaks free it just unscrews and the new one screws in to it's place. And you cut the connector off of the old sensor and just use the shrink tube to attach the new sensor to the connector. the threads should come with antiseize on them and it'll just screw back in. Done.

[lbrowne]

probably warm up the car to get it to break loose easier....

I think I'll do the cts first - try a tank of fuel, then the O2 sensor. I'll price them out this week and hopefully complete this weekend.

[ka24dave]

There is just one, it's on the exhaust manifold, and you have to have a special tool to get it out. (it's like $2 for the tool at any auto part store, just tell them what your doing and they'll know) because of where it's at.

It's going to be really really tight and a bear to get loose, but once it breaks free it just unscrews and the new one screws in to it's place. And you cut the connector off of the old sensor and just use the shrink tube to attach the new sensor to the connector. the threads should come with antiseize on them and it'll just screw back in. Done.

you forgot one important and very helpful thing, it helps tremendously to have some pb penetrator, that stuff works wonders on getting this lil bad boy out.

[lbrowne]

I wouldn't think I'd have to disconnect the battery to swap the cts - the O2 yes...

Anyways I picked one up, got a full tank and I'll be swappin out the cts today.

[ka24dave]

i didnt disconnect the battery on mine when i did the o2 sensor...as long as the key is off it is fine.

[KATwo40]

Uhhh...a 7/8" boxed end wrench fits the O2 sensor just fine.

[KATwo40]

..and i bought a bosch o2 sensor yesterday for $18...i still get a premium sensor

Those sensors are junk. I go through about three of those per year. They are notorious for going out pretty quickly on ALL cars. That's why they're only $18 instead of $50.

However, I still use them because I'm cheap.

[ka24dave]

Those sensors are junk. I go through about three of those per year. They are notorious for going out pretty quickly on ALL cars. That's why they're only $18 instead of $50.

However, I still use them because I'm cheap.

hmm...strange.. the ones we get here in fl are good i've seen some outlast the cars... anyhow mine is good, it has improved my 240's performance (slightly) and hasnt f-ed up so far... and it is cheap because you have to splice the wires yourself vs. getting a sensor with the plug in already attached to the end of it.

[KATwo40]

FYI: A slow O2 sensor isn't going to have any effect on open loop performance (your acceleration pull issue). The ECU only looks at the O2 for closed loop/light throttle.

And, like I said, regardless of whether or not they last, they're cheap and quick. I'm always game for savin' a few bucks.

[lbrowne]

Well its replaced, and I have a fresh tank of gas. We'll see what happens.

My car actually had this kinda of lag when you first got into 2nd and 3rd for a few hundred- 1k worth of rpm and then accelerated normally. I liked it to almost as if a clutch was slipping a bit, which mine isn't, but that sort of sensation.

I just took her for a burn and it appears that is not there anymore but I know better after driving her tomorrow for a longer distance.

[ka24dave]

yeah mine had that prob too. but mine still occurs randomly from time to time full throttle or partial throttle, it just lags after a shift for about 1k rpms. still trying to figure it out...the o2 sensor quickened it ever so slightly, but it is still a noticeable lag.

and FYI: open loop means the o2 sensor is NOT being used. the engine uses all sensors except the O2 to determine fuel delivery.

and open loop mode is only used during the below-operating temp range. and my problem isnt within minutes after startup like that during open loop. it is closed loop i have probs in.

and if your smart you would realize after buying 3 a year you could pay ten dollars more at the time of purchase and get a better one that will last you two years, thus saving you $90 dollars over the course of that period instead of you buying the bosch ones every time like you say you do. but hey, its your money....scary desicion tho dont ya think?


Modified by ka24dave at 12:48 PM 11/20/2006

[KATwo40]

Eh...you're wrong in your understanding of open and closed loop operation.

Open loop means "varying load and operation parameters."

WOT = open loop. Cruise = closed loop.

Not that it will get any more responses from me, as I was just trying to help with your problem, but I don't really see why you come on a forum, ask for help, then argue with everyone that tries to offer a tip. I couldn't give two craps if your car runs right or not. We don't do this because we get paid. We do it because we like to help.

Check your TPS adjustment. That's the most common cause of the surging situation.

Peace out.

[ka24dave]

What does the O2 sensor do?It is the primary measurement device for the fuel control computer in your car to know if the engine is too rich or too lean. The O2 sensor is active anytime it is hot enough, but the computer only uses this information in the closed loop mode. Closed loop is the operating mode where all engine control sensors including the Oxygen sensor are used to get best fuel economy, lowest emissions, and good power.

http://www.mr2.com/TEXT/O2_Sensor.html

pretty basic site for ya buddy. open loop is only used when the vehicle isnt within normal functioning temperature, and stays in open loop mode but when it is active, is stays in closed loop mode constantly regardless of throttle position. and your comments are unnessecary, i just argue with you (but by judging you turbocharge a heavy a** iron block, you cant be too smart anyhow.) so read up and enjoy

i came on here looking for help, not false opinions no how the sensor works. i need real answers not just shotty ideas from people turboing heavy iron blocks.

[neverlift]

L_O_C_Kthread now

[KATwo40]

What does the O2 sensor do?It is the primary measurement device for the fuel control computer in your car to know if the engine is too rich or too lean. The O2 sensor is active anytime it is hot enough, but the computer only uses this information in the closed loop mode. Closed loop is the operating mode where all engine control sensors including the Oxygen sensor are used to get best fuel economy, lowest emissions, and good power.

http://www.mr2.com/TEXT/O2_Sensor.html

pretty basic site for ya buddy. open loop is only used when the vehicle isnt within normal functioning temperature, and stays in open loop mode but when it is active, is stays in closed loop mode constantly regardless of throttle position. and your comments are unnessecary, i just argue with you (but by judging you turbocharge a heavy a** iron block, you cant be too smart anyhow.) so read up and enjoy

i came on here looking for help, not false opinions no how the sensor works. i need real answers not just shotty ideas from people turboing heavy iron blocks.

Sweet! I'm so glad to know that MR2 forums are the primary information source for Nissan ECU functionality!

For anyone else reading, that link above is inaccurate at best.

A non-heated O2 sensor (like you'll find in the early 240sx) will begin to function once reaching a temperature of roughly 450* F. However, the Nissan computer does not read the O2 sensor data in the entire fuel map. There are certain cells that are programmed to "read" the O2 sensor feedback. These cells are the idle and cruise load cells in the map, and NOT the moderate to heavy load cells. The narrowband O2 sensor will only reflect AFR's in the low to high 14:1 range (found during cruise and idle operation /GASP!).

If you get into re-programming (EEPROM tuning) the Nissan ECU's, you'll understand more about this.

Additionally, the primary source of fuel control for a Nissan MAF based ECU is the theoretical pulsewidth correction table. The ECU takes a voltage from the MAF sensor (according to it's mass airflow at the time the sample is taken) and converts it to a quantifyable number via the VQ (Volumetric Quantization) scale.

After obtaining a quantifyable number to represent the weightflow of air being injested, it then goes through a series of alghorithms using the K value to create a TP (Theoretical Pulsewidth for the injectors) that will yeild approx. 14.7:1 at any given engine operation condition.

Once the ECU has obtained a TP value, it then references the fuel correction table. The scales in the table are TP across the top and RPM down the side (these can be swapped to TP down the side and RPM across the top...doesn't really matter). At any given intersection of TP and RPM there is a correction value, which will modify the base injector pulsewidth to produce the desired fueling for that given operation load point.

These intersections are the "cells" which I described above, in saying that some have values to direct the ECU to use the O2 feedback and some don't.

To further support this, grab up a wideband O2 sensor sometime, or even just hit the dyno and do a couple pulls with their wideband O2 sensor installed. You'll find that the 240sx is VERY rich under heavy throttle operation, which is indicative of an ECU that's not looking at some magic fuel correction device.

Please, for the love of all engines, do not rely on the narrowband O2 sensor to correct your fueling for you in the heavy load areas, especially in a high-performance application.

And, ka24dave ~ Please, go adjust your TPS and your surging will likely stop.

[ka24dave]

i went to the mr2 site b/c it was the simplest way to inform you of your misguided sense of cars. the early 240's like mine work as i described, and i know it for a fact. so lets not hear any of this "dyno this, dyno that" garbage, as i wouldnt waste a minute on your theory. the ecu on a 91 240 isnt as complex as you make it seem. think back 15 years, you'll catch on eventually.

i started this thread to get solutions, if you have some, then please by all means feel free to post them. if you came on here to start a forum-flaming war, then get the hell off my thread.

.....and now for a response from another moron.....
Modified by ka24dave at 1:51 PM 11/23/2006

[neverlift]

katwo40sx stop! you have a very good understanding of th eccs dont kill yourself trying to explain.You clearly did almost word for word.

[lbrowne]

So far I this tank I'm not really noticing a difference, but its so cold out now I always find with any vehicle I've the really cold months.ownded that the mpg goes down during the really cold months.

[rsmithdrift]

KA24dave.......Your a moron.

Even My Z31 worked EXACTLY as KATwo40 described. And I mean exactly.......especially since it's the same damned ECU. And that car is now 22 years old.

And the MAF and the O2 sensor are.......Gasp....... Exactly the same. The only difference is that the ECU for my 1984 300zx is programed with maps for a 3.0 VG30E v6.

The parts won't trsnsfer over directly because they are shaped different to fit the car, but I assure you they work the same.

I had MAJOR problems with my Z and they were all caused by a faulty MAF sensor. O2 sensor will only affect MPG and part throttle (Closed Loop) operation. My manual for the car confirmed this in every way.

Fuel injection has been around for a LONG time bro. Don't make assumptions about it being primitive based solely on age.

Also, my friend who built his own VW whatever that thing is, it's a 85 and he programs his factory ECU the same way as on a NISSAN with MAF controlling the AFR and 02 being blind under WOT.

NISSAN calls WOT close loop "Blind Mode" because it ignores it's emission controls. 02 is one of them.

Many of nissan specialists confirmed this when I was trying to figure my Z and it's problems out.

I have already told you CTS is a main problem with powerband, but I don't think that's the problem with your car. The CTS works by telling the ECU how hot/cold the engine is and letting run lean/rich accordingly. If it's cold it'll choke and lean out, otherwise it'd stall. If it says it's too hot, it'll run rich to cool the engine down. If it goes bad the one on my Z always says it's -200* and you can imagine how lean it would try to run. It wouldn't even start when that happened. The 240 CTS sensor on the other hand quits sending a signal when it goes out, and that puts the car into safe mode, which makes the car run slightly rich untill 5500 rpm, even then it runs slightly rich. BTW, when the CTS sensor says the car is at operating temps, it is ignored untill it see's something it doesn't like, such as too hot or too cold or no signal at all, and then it adjusts as necessary.

My car pulls strong and even from 3500 to 6500 and peaks at 4800. Everything is new on my car and my timing is set to 25*

With 20* it pulls strong 3200 to 6100 and peaks at 4.5k.

Your car runs fine, welcome to 4 bangers. I miss my old Z for this very reason. Nothing like making good power at 2500 rpm....

[KATwo40]

^^^ Some of us "stupid" people have been able to make some power by turboing a heavy truck motor.

But what do we know?

[ka24dave]

@rssmithfdrift: i dont give a F about you or your car. if you actually read this entire thread instead of trying to bash me you will realize i already replaced my CTS. that helped a very little bit. next time read before you make yourself look like a jacka**

and yes, fuel injection has been around for some time, and i never made an assumption on anything. and please dont start off a post by calling me a moron, then by being nice in the end of your speech....(skitzo???)

@ka-t moron: wow you made 80 extra hp?? i could make the same power with a lighter aluminum block.

remember its not just power, its also weight that counts.

[KATwo40]

If you'd get over your ego long enough, you'd see that I already offered a solution to your surging sensation several posts back.

For some reason, you got all oppositional toward me after my first post in this thread, when in fact, I was trying to help you by pointing out that the O2 sensor isn't the problem here.

After you continued to argue that point, I even offered a detailed explanation of how the ECCS works (Nissan tuning system).

It's too bad you refuse to let us help you and accept the fact that we're all car guys here and we all enjoy tinkering with them. You like N/A, I like F/I. Some people like drag racing, some like road racing.

Who cares about the differences? Why not just let people help you and be willing to possibly learn something new and risk being wrong about a system or concept? No one is perfect, man. There's much I don't know about these cars, but I'm not afraid to admit it.

You seem quite adament about finding the fix for what you perceive as an issue with your car. I hope someday you can focus that energy positively so we can do what normally is done on forums -gladly exchange information with one another in an effort to expand our knowledge of the subject matter.

Silly bickering back and forth gets us nowhere and doesn't fix your car. I'll openly admit, it's difficult to refrain from reacting to someone's insulting opposition, especially when the insults are clearly personal. But, we're only human.

I'll post it for the third time, ka24dave. PLEASE, go check your TPS adjustment.

Here's why:

The ECU does not use the TPS to calculate engine load, but rather to adjust for throttle tip-in (compare these to the function of an accelerator pump in a carburetor) and decel compensation. If the TPS adjustment is off, the ECU will either undercompensate or overcompensate for a given throttle angle and cause a surging sensation during a steady heavy throttle pull.

Yes, I could be wrong. But this is the most likely problem.

[Jookmasta]

i had a similar issue with my car and it turned out to be the knock sensor................if all else fails, replace that............

[ka24dave]

just to firstly clarify, if you hadnt acted like a jacka** to me, i wouldnt have to you in return. You just have to look at it from its perspective, you cant exactly be here to see and feel the problem, thus can only make a relative assumption of the problem, i've exhausted all solutions i've heard so far and have had no better results.

If you'd get over your ego long enough, you'd see that I already offered a solution to your surging sensation several posts back.

For some reason, you got all oppositional toward me after my first post in this thread, when in fact, I was trying to help you by pointing out that the O2 sensor isn't the problem here.

After you continued to argue that point, I even offered a detailed explanation of how the ECCS works (Nissan tuning system).

It's too bad you refuse to let us help you and accept the fact that we're all car guys here and we all enjoy tinkering with them. You like N/A, I like F/I. Some people like drag racing, some like road racing.

Who cares about the differences? Why not just let people help you and be willing to possibly learn something new and risk being wrong about a system or concept? No one is perfect, man. There's much I don't know about these cars, but I'm not afraid to admit it.

You seem quite adament about finding the fix for what you perceive as an issue with your car. I hope someday you can focus that energy positively so we can do what normally is done on forums -gladly exchange information with one another in an effort to expand our knowledge of the subject matter.

Silly bickering back and forth gets us nowhere and doesn't fix your car. I'll openly admit, it's difficult to refrain from reacting to someone's insulting opposition, especially when the insults are clearly personal. But, we're only human.

I'll post it for the third time, ka24dave. PLEASE, go check your TPS adjustment.

Here's why:

The ECU does not use the TPS to calculate engine load, but rather to adjust for throttle tip-in (compare these to the function of an accelerator pump in a carburetor) and decel compensation. If the TPS adjustment is off, the ECU will either undercompensate or overcompensate for a given throttle angle and cause a surging sensation during a steady heavy throttle pull.

Yes, I could be wrong. But this is the most likely problem.

No sh** the o2 sensor wasnt the prob. that was just a battle you liked to try to wage on me.

and for the love of CARS please stop with the TPS garbage, that is NOT my problem, if it were, i would have posted back after your first uneducated guess.(im not attacking you on this, but you seem to have an obsession with TPS)
Modified by ka24dave at 11:23 AM 11/27/2006

[KATwo40]

Did you try the TPS adjustment at all? Only reason I keep bringing it up is because you never responded with a "tried the TPS adjustment and it didn't work."