SR TPS question [Archive] - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

SHIFT_*grind*

10-05-2008, 07:24 PM

My car runs like shit. It starts up really rough, idling extremely low, sometimes stalling. Eventually the idle stabilizes at ~850RPM, but I can still hear it missing. The car barely accelerates; it can't handle any sort of load without missing and sputtering.

When I check the TPS per the FSM instructions, the resistance reading with the throttle wide open is ~10k ohms, twice what it should be. So I buy one from a member who's parting out his perfectly running car. This isn't a noob with 5 posts, he's sold plenty of parts so I'm inclined to believe him. I put this sensor on my car, it reads exactly the same: ~10k with the throttle wide open. Car still runs like shit.

What's up? It seems like I got another bad sensor, but why would his car be running fine with it? Are they easy to damage? His car was running a MAF-based PowerFC, could that have anything to do with it?

Here are the possibilities I can think of:

1) The sensor I got is bad; maybe it's fragile and got damaged in transit, who knows.
2) I'm an idiot, and am measuring resistance wrong (although I don't know how this would be possible) and something else is causing my problems.
3) The S13 SR TPS is different from the S14, and should read at ~10k ohms at WOT. The FSM I have is the one for the S14 SR20, since the S13 SR FSM is fairly unattainable.

Someone help me out, seriously.

projectRDM

10-05-2008, 07:27 PM

I'm almost certain the TPS is different between chassis. They are on KAs anyway. Is yours a flat plastic sensor with a 3prong plug on one end, or does it have two 3prong plugs?

((sr)) kelly

10-05-2008, 08:04 PM

its really weird... but the symptoms of your car dont resemble a bad tps to me.. my friends sr20s TPS was bad and it didnt act like that at all..

do you know anyone with a running sr20 near you?? you can transplant parts untill you pinpoint the culprit

rps13drift

10-05-2008, 08:06 PM

Sounds like a ignition problem dude!

UNISA JECS

10-05-2008, 08:09 PM

I believe the FSM is wrong about the ohm's, its reversed IIRC.

It should be;

Throttle posistion

10 ohms closed
2 ohms fully open

Heres anotehr thread where someone was thrown off to:
http://zilvia.net/f/tech-talk/136620-tps-reading-wierd-ohm-values.html

UNISA JECS

10-05-2008, 08:25 PM

Also for the Automatics its backwards to on the continuity test.

This guys also caught it here:

Testing TPS with multimeter: 240SX Technical Forum: Nissan Forums / Infiniti Forums - NICOclub (http://forums.nicoclub.com/zerothread?id=352953)

d-magic

10-05-2008, 10:43 PM

Do you have ticking noise associated with your problem. If so, pull your valve cover. I thought that my cam timing was off. That's the same problem i was having today, and found #4 exhaust rocker to come out. It was a nightmare, cause i think that one of my shims fell in the oil pan. I've been pissy since then.

SHIFT_*grind*

10-06-2008, 07:39 AM

I'm almost certain the TPS is different between chassis. They are on KAs anyway. Is yours a flat plastic sensor with a 3prong plug on one end, or does it have two 3prong plugs?

Single 3 prong plug, I think the one with twin 3 prong plugs is the auto sensor. According to phase2 (http://phase2motorsports.stores.yahoo.net/srtpsse.html) they're all the same, but that's hardly definitive.

its really weird... but the symptoms of your car dont resemble a bad tps to me.. my friends sr20s TPS was bad and it didnt act like that at all..

It made sense to me at first; the fact that I can't change throttle position without sputtering makes a bad TPS seem plausible. I don't know anymore, though.

I believe the FSM is wrong about the ohm's, its reversed IIRC.

It should be;

Throttle posistion

10 ohms closed
2 ohms fully open

Heres anotehr thread where someone was thrown off to:
http://zilvia.net/f/tech-talk/136620-tps-reading-wierd-ohm-values.html

That looks like it's for a KA.

I'm not sure how the TPS could be on upside down; there's only one way it can bolt to the throttle body. Resistance definitely goes up with the throttle. I'm starting to think the FSM might be wrong about the values though, or that the S13/S14 TPS sensors might be different, like projectRDM suggested.

At any rate, since two different sensors (one from a perfectly running car) showed the same resistance values, my problem is probably somewhere else?

Injectors are all dead on at 11 ohms. I tested the resistance on the coil packs and they all seemed fine; could one of them have gone bad and still test fine with a multimeter?

Could it be something as simple as a boost leak? The car boosts fine, just doesn't have any power. I don't get that staccato machine-gun backfiring, so I don't think it's the timing.

Compression? :(

ROIDMONKEY

10-06-2008, 08:19 AM

my car kinda do the same.. when is cold only tho.. after like 10 mins running it got fix by itself.. those firs 10 mins runs lean lean thats why u feel ur car rought .. i change so far coil packs /TPS/ ECU coolant temp/ check vacum lines and other shit.. next thing and im very sure is what is causing my problem(after changing all that LOL) its the Idle control

SHIFT_*grind*

10-06-2008, 09:44 AM

Yeah, my car runs like ass all the time. :(

Here's a link to another thread with more details on my setup, and problems: http://zilvia.net/f/tech-talk/212263-sr-sputtering-bogging-misfiring.html

SoSideways

10-06-2008, 11:30 AM

Hmm...

Shouldn't you check for Volts as well?

Ohms is only really telling you whether or not it's getting power, not getting power.

Volts will tell you if the brushes inside are working properly or not.

IIRC, at idle, the TPS values should read around 0.42 Volts (the default range should be like 0.30 Volt to 0.60 Volt), and at WOT it should be approximately 4 Volts.

SHIFT_*grind*

10-06-2008, 11:48 AM

Ohms is only really telling you whether or not it's getting power, not getting power.

But it's not getting power at all, because the resistance test is done with the harness unplugged. Voltage readings are taken with the harness plugged in, car running and warmed up.

I haven't checked the voltage because according to the FSM, the resistance is way off and it means the sensor is bad and needs to be replaced.

SoSideways

10-06-2008, 12:16 PM

But it's not getting power at all, because the resistance test is done with the harness unplugged. Voltage readings are taken with the harness plugged in, car running and warmed up.

I haven't checked the voltage because according to the FSM, the resistance is way off and it means the sensor is bad and needs to be replaced.

So have you replaced it?

SHIFT_*grind*

10-06-2008, 12:23 PM

That's what I'm saying; I replaced my TPS with one from another member who's parting out a perfectly running car, and there was no change. The resistance was off on his as well.

It's possible that a) both sensors are bad, even though his car was somehow running fine (I bought it from ((sr)) kelly up there), b) both sensors are perfectly fine and the S14 SR FSM lists the wrong values for what the resistance should be, (or the S13 SR TPS sensor is different from the S14 SR TPS) or c) I'm a complete idiot and am measuring the resistance wrong, even though I followed the FSM to a T.

UNISA JECS

10-06-2008, 12:41 PM

Did you tottally miss my post about the ohm specs in teh FSM are ass backwards?

ROIDMONKEY

10-06-2008, 12:44 PM

U can also recalibrate ur TPS if u have a stand alone ecu... not sure how with stock .. that helps too

SHIFT_*grind*

10-06-2008, 12:58 PM

Did you tottally miss my post about the ohm specs in teh FSM are ass backwards?

No. Did you miss this one?

That looks like it's for a KA.

I'm not sure how the TPS could be on upside down; there's only one way it can bolt to the throttle body. Resistance definitely goes up with the throttle.

This looks like a KA to me:

http://farm1.static.flickr.com/170/417026689_4f98a122f5_o.jpg

On my car, the resistance goes up with the throttle, just like the S14 SR FSM states...it just goes up much higher. But if the FSM you posted lists the specs backwards, maybe the S14 SR FSM just lists the wrong WOT resistance...

SHIFT_*grind*

10-07-2008, 06:35 AM

I checked the ECU and got code 34: detonation/knock sensor. No TPS code, so......I guess it's fine, and I have other problems?

sbc

10-07-2008, 04:51 PM

The TPS is different from s13 to s14 SRs. I got mine from west covina/thenismoshop for like $40.

I also had trouble with the resistance but I set it using voltage instead and figured that was fine.

UNISA JECS

10-07-2008, 05:40 PM

No. Did you miss this one?

This looks like a KA to me:

http://farm1.static.flickr.com/170/417026689_4f98a122f5_o.jpg

On my car, the resistance goes up with the throttle, just like the S14 SR FSM states...it just goes up much higher. But if the FSM you posted lists the specs backwards, maybe the S14 SR FSM just lists the wrong WOT resistance...

The S13 KA and S13 SR and for that matter the B13 SE-R TPS spec the same and follow the same resistance test, I knew of this since about 2000.

aguadilla

10-07-2008, 08:59 PM

Have you noticed any black smoke upon startup? What about vacuum leaks? Have you checked your fuel pressure regulator, pull the vacuum line off and see it there is any gas in the hose. Anyhow hope this helps.

UNISA JECS

10-07-2008, 09:13 PM

Ok SHIFT *grind* dug this up for you and look it says SR20DET, even the japanese FSM is incorrect, and no this isn;t photochoped...haha

http://i167.photobucket.com/albums/u159/zilvia_album/KA24DE%20REBUILD/SP32-20081007-201114.gif

http://i167.photobucket.com/albums/u159/zilvia_album/KA24DE%20REBUILD/SP32-20081007-201117.gif

http://i167.photobucket.com/albums/u159/zilvia_album/KA24DE%20REBUILD/SP32-20081007-200651.gif

slider2828

10-07-2008, 09:23 PM

I am almost thinking his ecu is bad.... Did you fry any fuses or spark anything while working on your car? Replace the Ecu and try again.

slider2828

10-07-2008, 09:31 PM

OHM testing and voltage testing for TPS is different too. OHM testing is testing when it is unplugged. Voltage testing is when the TPS is plugged in. Come on now...

Secondly replace your knock sensor, you can use KA or even Sentra SER SR20DE

SHIFT_*grind*

10-08-2008, 06:40 AM

The S13 KA and S13 SR and for that matter the B13 SE-R TPS spec the same and follow the same resistance test, I knew of this since about 2000.
......
Ok SHIFT *grind* dug this up for you and look it says SR20DET, even the japanese FSM is incorrect, and no this isn;t photochoped...haha

Thanks for that!! That at least shows definitively that the S13/S14 sensors are different...do you know where I can find that entire S13 SR20DET FSM?

The thing I don't understand is......you're saying that the TPS resistance is actually backwards from what the FSM says. ~2k ohms at WOT, ~11k ohms resting. I've tested two separate TPSs, one from a perfectly running car, and they do not work that way. The resistance increases as the throttle goes down. There is zero possibility of them having been put on backwards.

It actually makes more sense to me now seeing the S13 SR FSM, where it specifies ~2k resting, ~11k WOT...that's fairly close to the ~1k/~10k that I observed.

Have you noticed any black smoke upon startup? What about vacuum leaks? Have you checked your fuel pressure regulator, pull the vacuum line off and see it there is any gas in the hose. Anyhow hope this helps.

No black smoke. I don't think I have vacuum leaks, but I've been trying to put together a boost leak tester to find out for sure. Pressure regulator is a newly installed Nismo adjustable (yeah I know, not the absolute greatest) and my fuel pressure is fine, 36/43.

I am almost thinking his ecu is bad.... Did you fry any fuses or spark anything while working on your car? Replace the Ecu and try again.

When I was installing a couple of gauges, I did some dumb shit with the relays and melted a wire going to one of my radiator fans :( But, that circuit involves the battery, a relay, and a toggle switch; I'm not a wiring expert, but it shouldn't affect the ECU. Before and after that, it drove mostly fine, with some hesitation at part throttle in the middle of the rev range. It's gotten progressively worse and now it's bad enough that I can barely accelerate at all and it often stalls upon startup.

The progression makes me think of a part, like a sensor, gradually going bad and making the car run worse in the process. If I did something like fry the ECU, it would probably immediately make the thing run God-awful-miserable :p

SoSideways

10-08-2008, 08:35 AM

So... have you replaced or at least looked at the knock sensor yet?

SHIFT_*grind*

10-08-2008, 08:42 AM

SoSideways

10-08-2008, 08:52 AM

I haven't had a chance yet; just pulled the code yesterday and I'm at work all day :(

Whether the knock sensor is causing all my problems or not, it's pretty clear that it's gone bad (or maybe the wiring has), so I'll take a look at the wiring, replace the sensor if necessary and see where it gets me.

I would say, to just go over there and look over the wiring, and at least stick the multimeter on it to check the sensor to see if it is still reading within the parameters called for by the FSM.

If it is indeed bad, then at least you know by replacing it, that you're 1 step closer to a good running car, maybe even fixed the problem completely :)

SHIFT_*grind*

10-08-2008, 09:07 AM

Yeah, I'll definitely check it with the multimeter before replacing it, they're ~$150 new.... :ugh:

WILDACEX187

10-08-2008, 10:35 PM

SHIFT_*grind*

10-09-2008, 06:25 AM

sorry to thread jack but i am interested in this also. i have this problem on my car YouTube - car (http://www.youtube.com/watch?v=1XJEmICRsuM) . when i give my car partial throttle it makes the rpms jump around

i connected my friends power fc to check tps voltage and it was reading 0 volts at closed throttle and 3.90v at WOT. is that right? im about to take the car to a shop next week cuz this is driving me crazy

The car is doing that by itself? The revving up and down between 1k and 2k? I had that same problem on my RB20 S13. It happened because I took the IAC valve off to clean it, and unwittingly lost the little spring that was inside it and put it back together without the spring. It pissed me off so much because it would just constantly rev up and down once the car was warmed up; I had some redneck in a lifted Ram try to race me because he thought I was revving on him :rolleyes: I finally realized what was wrong, pulled the IAC valve from a B13 Sentra in a junkyard, took the little spring from it, and put it in my IAC valve. No more problems.

So, all that is to say......maybe check your IAC valve, if you haven't already.

SHIFT_*grind*

10-09-2008, 08:19 AM

Might this have anything to do with the fact that I switched to BKR7ES plugs (copper) from BKR7EIX plugs (iridium)? Copper plugs apparently give a better spark than iridium and just need to be changed more often, and they only have a few miles on them, but......the car had iridium plugs in it the last time it ran right.

SoSideways

10-09-2008, 08:38 AM

sorry to thread jack but i am interested in this also. i have this problem on my car YouTube - car (http://www.youtube.com/watch?v=1XJEmICRsuM) . when i give my car partial throttle it makes the rpms jump around

i connected my friends power fc to check tps voltage and it was reading 0 volts at closed throttle and 3.90v at WOT. is that right? im about to take the car to a shop next week cuz this is driving me crazy

As for you, have you ever checked the FSM?

The TPS voltage should be between 0.3v and 0.6v at the closed position, and should be approximately 4v at WOT.

I have mine set to 0.42v in the closed position, and 4.07v at the WOT position.

Might this have anything to do with the fact that I switched to BKR7ES plugs (copper) from BKR7EIX plugs (iridium)? Copper plugs apparently give a better spark than iridium and just need to be changed more often, and they only have a few miles on them, but......the car had iridium plugs in it the last time it ran right.

I highly doubt going from copper to iridiums would cause your car to "not run right".

Have you checked your KNOCK SENSOR yet? lol

Geez dude, quit dancing around the bushes, check it, then report back the results. If you don't find anything wrong w/ the knock sensor or its circuits, then we could look for other possibilities, but right now, all symptoms point towards the KNOCK SENSOR or its circuits.

SHIFT_*grind*

10-09-2008, 08:40 AM

I know I know I know, I will. Tomorrow. I have 0 time to even touch the car during the week, but I have tomorrow off. In the meantime I'm just speculating =P Trying to think of info I haven't mentioned to see if it jumps out at anyone.

I went from iridium to copper, not the other way around.

SoSideways

10-09-2008, 08:45 AM

Either way, the plug change shouldn't change the way your car drives that dramatically, unless there was already an underlying problem.

Since the coppers do burn a little hotter, it is possible that the faulty KNOCK SENSOR is now picking up some noise generated by the hotter burns of the copper plugs, thus triggering your ECU to go into "limp home mode".

SHIFT_*grind*

10-09-2008, 08:53 AM

KNOCK SENSOR

...

KNOCK SENSOR

KNOCK SENSOR

I get it, I'll check the knock sensor. :p Stuff just piles up, I gotta change the serpentine belt and a strut mount on my wife's car too. I miss the college days when I could just come home from school every day and start wrenching. Now it's like, one day every 2 weeks is designated "fix car shit" day :(

SoSideways

10-09-2008, 08:59 AM

I get it, I'll check the knock sensor. :p Stuff just piles up, I gotta change the serpentine belt and a strut mount on my wife's car too. I miss the college days when I could just come home from school every day and start wrenching. Now it's like, one day every 2 weeks is designated "fix car shit" day :(

I know how it goes man.

My car's STILL DOWN from like 3 months ago, and we're moving out of this house on Saturday, and I won't get the last part to put the car back together in 1 piece until Saturday.

After that, I still need to put coolant in it and bleed it (I can do that on the driveway since it's sloped, will help the process go faster), THEN I can drive it to the new place.

Talk about having no time to do stuff... I gotta figure out why my front coilovers are being bitches and won't turn, since I have to raise the front of the car like half an inch... instead of loosening the collars and just turning the shock bodies, I gotta take the bolts off of the lower bracket and spin them that way... hopefully they're not seized.

FUN DAYS AHEAD!!

SHIFT_*grind*

10-09-2008, 09:24 AM

Yeah, the last time my car really ran was late June. I'm tired of this, I want to just get rid of it and get a stock S14 or something and not mod it. Really, I won't mod it this time. Promise.

........

WILDACEX187

10-09-2008, 12:31 PM

its not doing it by itself, its doing it when i give it partial throttle. if i give it alot of gas its good. somebody told me i have a lazy tps which is not giving me the voltage i need. i tried to move it but the car wouldnt even start when i had it at WOT at like 4.16v

SHIFT_*grind*

10-10-2008, 01:21 PM

The knock sensor might as well be welded to the fucking block. Goddamnit. I hate cars.

SHIFT_*grind*

10-11-2008, 11:12 AM

OK. A word of advice, to anyone who's going to be taking off their knock sensor.

1) Go ahead and change your fuel filter at the same time, so it'll be out of the way.
2) Remove your intake manifold support bracket, and toss it, if you haven't already.
3) Take the starter out. Two bolts, it takes like a minute and will give you SO much more room.
4) Jack the car up and get at it from underneath.

It will save you a LOT of time and aggravation.

I got the knock sensor off. Just looking at it, it looks fine...no cracks or anything like that. I took the sheath/wrapper off of the knock sensor harness, though, to see if anything looks bad in there......is it supposed to look like this??

http://smg.photobucket.com/albums/v245/bigjay00213/100_1286.jpg
http://smg.photobucket.com/albums/v245/bigjay00213/100_1289.jpg

SHIFT_*grind*

10-11-2008, 05:25 PM

Does that look normal......?

SHIFT_*grind*

10-11-2008, 08:53 PM

Someone tell me this......in this picture here:

http://smg.photobucket.com/albums/v245/bigjay00213/100_1289.jpg

Toward the right side, right by the plug that connects to the sensor, you can see the wire kind of hanging free. I haven't cut anything open, but I assume this is the harness' ground wire that shields the signal wire.

Is it supposed to be just hanging free like that, or should it be connected/grounded to something?

SHIFT_*grind*

10-13-2008, 09:26 AM

OK. I did the following:

1) Checked for continuity between the signal pin of the knock sensor, and the back of the sensor. It's fine. 5.6 M ohms of resistance, if I'm reading it right. So, the sensor is fine.
2) Checked for continuity in the wiring harness, between the knock sensor harness signal wire and ECU harness pin 27. Again, no problems.
3) Reconnected the knock sensor and the subharness, grounded the sensor to the engine (by laying it on the intake manifold), and checked for continuity between ECU harness pin 27 and engine ground. Once again......all fine.

All the wiring between the ECU and knock sensor seems to be fine. Including the sensor itself.

At this point, the FSM says to check the ECU terminals for damage (there's none), erase the code, and test drive. Somehow, I don't think I fixed my problem. Should I be looking for a short somewhere?

Someone chime in here. Please.

slider2828

10-13-2008, 11:10 AM

That harness looks like sh!t.... it does not look like that normally.... come on factory wouldn't put something in that looks like that and knock sensors are sensitive to electrical irregularities...

SHIFT_*grind*

10-13-2008, 12:32 PM

I thought it looked like shit as well, but I also tested it with the multimeter...only had continuity between the two ends of the signal wire, and then continuity between the ground pin and the wire hanging off the end (meaning no shorts in between). So while it looks ass it appears that it works properly...

Should I try to buy a new subharness? Or make one?

slider2828

10-13-2008, 12:46 PM

Well all you can do is unplug all the power, reset the ecu and try again... Also remember to get out of the error mode and into the regular drive mode... See if your ecu flashes errors again.

SoSideways

10-13-2008, 12:51 PM

Is the ground/shielding on the right side of that picture there touching a bare signal wire? Or is it just touching the signal wire's cover?

Because the ground wire/shielding should not be touching the bare signal wire... if they're touching, then that's a short, and will cause your sensor to not work properly.

Try to see if you get continuity between the signal wire and the grounding/shielding on the wire. If you get continuity, that means they're shorted out somewhere along that piece of wiring.

SHIFT_*grind*

10-13-2008, 01:01 PM

Try to see if you get continuity between the signal wire and the grounding/shielding on the wire. If you get continuity, that means they're shorted out somewhere along that piece of wiring.

That's what I meant here:

I also tested it with the multimeter...only had continuity between the two ends of the signal wire, and then continuity between the ground pin and the wire hanging off the end (meaning no shorts in between).

The shielding wire on the right side of that picture only had continuity with the ground pin on the harness.

Ugh, I hate my car.

SoSideways

10-13-2008, 01:21 PM

You said you only checked between pin 27 on the ECU harness and the signal wire pin on the end of the harness by the intake manifold...

Did you check the ground on that harness?

I forget if the ground is tied to the ring terminal grounds on the intake manifold or if it's clumped into the nest of grounds and grounds into the ECU or what, but you should check that out and see what's going on there.

SHIFT_*grind*

10-13-2008, 01:25 PM

It's tied to the ring terminal grounds on the intake manifold, two of them. I did notice that the two ring terminals were bolted to the same spot for some reason, so I separated them...I couldn't imagine that doing much though. I'll check for continuity between the shielding wire (in the picture) and the intake manifold.

That shielding wire is supposed to be just hanging there that way, then? I mean, it wasn't just hanging free, it was taped up in the wire sheath I took off, but still...