casio

My car has hesitations, wont idle when started (has TB mod), hits a 2500rpm wall when cold, and has a 2500rpm hesitation (very frequently) when warm. runs better after that, but i believe there's more power to be found in the top-end (untuned s-afc installed). failed 15mph emissions test (1800rpm).

my car's check engine light doesn't always work, but i pulled codes when it was on. i got a 9 and 13; or thermosensor and pressure sensor. finding pressure sensor threads was no fun, but i gathered enough to at least test volts. actually, the wire colors were different, but common sense got me through i believe. i would like to add that, what i found funny, was there was 4 inputs listed, just as the plug has 4, but only 3 used on my sensor. this brings me to Wayne88n/a's question about the 12v wire. Wayne, i only got 5v (actually 4.8v i believe); no 12v.
my wires were Brown/Black - Ground; Brown/White - 5v (ref?); and Green/Yellow - Signal out.
well, having a pressure sensor code, i decided to see what that dealy, yo. first, for a reference, i tested at the sensor. with my bad (semi-erratic; i assume cold engine, normally idles fine) idle (say 600-800 give or take), i was putting out 2.8v-2.9v. alrite, fair enough. i found someone's volt numbers, but i think it was turbo. so, for me, 2.8-2.9volts is normal. then i test at the ecu. inbolting and twisting over, i stick in my wire, find a ground and check. a steady 2.9volts (so 2.8-2.9v). exactly at the sensor.
so, with a perfect voltage transfer from sensor to ecu, why would i get a code? i havent had the sensor unplugged or hose off since i reset codes.

casio
91 n/a

casio

something that confuses me is what happens when you have a code. for instance, say my ecu was getting no voltage from my pressure sensor's signal wire. this, not being intermittent or a one time thing, would make sense to throw a code resulting in the "intake pressure fixed at 760 mmHg (29.9 inhg)." however, what if a problem is intermittent, happened once, or is only in part of the potentiometer's (sensor; whatever type of variable voltage accessory it may be)?
for instance; what if i were to unhook the vacuum line (throwing a code i assume) and reattaching it? this would be an example of a one-time error. or, like some people have claimed, had a "bad spot" in the afm (though i'm not sure if its worthy of a code, just an example)?
mainly what i'm asking is, if something throws a code and the ecu is not reset, does the ecu acknowledge that the sensor works and continue to read it, or does it instead use its own 'fixed input' in case of a bad sensor?

(it seems hard to word, yet its a simple question)

WAYNE88N/A

Damn, you want me to read all that, lol...

You have an S5- I do believe that you guys have no 12v input to your pressure sensors or atmospheric pressure sensors like the S4's do...

The 2500 wall when cold- is that due to your secondary throttle plates not opening because of the thermovalve and dashpot doo-hickey?

We've been over this before- what are your readings at the ECU from the thermosensor?

2.9v at the pressure sensor input sounds kind off high at idle, leave the meter on, and advance the throttle- does the voltage increase towards 4.8v?

Why do you get a code? Hell I can't even figure out why I get a code, lol. Every time I get on her, bam, there goes the boost sensor code on my "real time" LED setup. Doesn't affect performance, though, so I don't worry about it. Just pretty flashing red lights at this point. Started after I installed the open exhaust; the voltage numbers look good, the vac gauge looks good. Beats me. Moral of the story- if your voltages increase in a nice linear fashion from that boost sensor input while driving, don't worry about it just yet.

If the ECU sees a total loss of signal, I would think it would use its stored "fail-safe" signal. But if it's an intermittent type thing (like my boost sensor codes) with good signals MOST of the time, I wouldn't think the ECU would keep jumping back & forth between the inputs and its stored code, that's just conjecture at this point...

BTW, I'm pretty sure that my boost sensor codes are because the pressure sensor and something else (AFM, maybe?) don't agree with what the ECU thinks they should be at a particular point on a romp (because of the different exhaust flow???), NOT because there is anything wrong with the boost sensor input...Again, conjecture

casio

my throttle body has the "mod" done, whatever all that entitles. BDC did it for me during my engine rebuild. i dont think i have either of those things listed. seriously, at 2500 rpm, the car stumbles so bad its like the brakes are on. i literally am slightly thrown forward.

i am yet to check the thermosensor. in fact *shhh* i dont even know where it is. i'm told its near the water pump, but i forget where. i guess i should be testing at the ecu anyways. before i did that, though, i would like to see if its plugged in or has a broke wire near the sensor (etc).
also, when the thermosensor fails and the ecu goes fail-safe, the temp is set at 176F. this is very close to normal op temps, especially for my n/a with a koyo. i'm not seeing how this could cause the 2500 wall(cold)/hesitation(warm). likewise, i dont see why my pressure sensor would cause it (unless it had a dead-spot; but as far as i know, there's no wear-part that could cause a dead spot). i have an extra tps i may hook up and see how the car reacts.

as hard as it was, i held the two wires i had jammed in the pressure sensor to the pins on the voltmeter and revved the engine. i remember seeing 3.xx and 1.xx, but i forget which one was higher rpm and which was letting off. i guess i should do the test again (but i hate rigging wires into the sensor's attachment/plug; why must test volts be so difficult?).


side note: the code on the pressure sensor is N350, which i believe is cali's ecu code; my ecu being N351 and convertibles being N353. interesting? not really. thats why its only a side note.

casio

haha, ive read some of your posts. they make my posts look like a seuss book next to a stephen king book !
i cant help it, i try to be specific.

WAYNE88N/A

Testing voltage is so hard because you're not doing it at the ECU, lol...

Here's my numbers from my boost sensor- yours will probably be a bit different, but should follow the same pattern:

Key on- 3.5v
750 idle- 1.25v
highway cruise- 1.8v
WOT- 3.3v
decel- .2v

And while you're down there at the ECU, check the voltage on that thermosensor too (have no idea which pin it is on S5's):

1/4 gauge- .5v
warm engine (to touch)- 1.1v
cold engine- 1.85v

This guy is the little green plug behind & below the alternator, on the back of the pump housing. They do get broken very easily, especially if any alternator removals have been done (the big bolt's nut at the back likes to turn its "tab" into it when tightening the bolt), been there, done that

casio

damn, i gotta try to rig this crap up and watch voltage when driving ?! might i ask how _you_ go about this? i think the easiest way would be to splice into the wires and solder a wire that can easily be used to test voltages, similar to how the safc is spliced into the wiring harness. i also need some gator clips. all i have is 22gauge solid copper wire (no idea what max amp/volt load), a volt meter, and ONE gator clip (attached to wire and male end; used for code checking). doesnt make code checking while drivig a walk in the park.

i hate that the FSM makes all sensor tests for OHMs. honestly, not in my entire life have i ever tested OHMs. with my luck i would blow the meter. i dont know how to test ohms, though i know i could search and find out pretty quickly.

casio

note: thermosensor - pin 2E (i found the ecu terminal sheet in the FSM finally; not the schematic, but just as helpful. tells voltage references, too)

your temp gauge reads different from S5s; warm engine is _just_ under half whereas, from everything i've read, S4s are 1/4. i assume your "1/4 temp gauge volt reference" is fully heated/warmed up engine.

FSM says: Idle/Engine Cold - .4v-1.8v
Water Temp; 68F - approx 2.4v
nothing about a fully warm engine.

casio

this time around i was having trouble getting a reading from the prssure sensor at the ecu. you know, i already tested once and found that i got the same numbers at the sensor as at the ecu, so i think i'm safe to test at the sensor. my car idled a few minutes and i got uncomfortable, so i'm gonna wait a minute before i test the pressure sensor again. but when i do, i'm testing at the sensor.

as for the thermosensor, i was getting off the wall readings. they wouldnt make up their mind. i would like to start off with the simple fact that everything was reading in negative; same goes for pressure sensor. i know this can mean the leads are just backwards, but i swore it was reading positive earlier when i tested the pressure sensor. anywho, the thermosensor's voltage would go as high as (-)4.9 or as low as (-)1s. it was erratic to say the least. if i changed my ground, it was a different voltage. if i kept it, it would fluctuate.
in my mind, when a sensor is messed up, it would either be all (sensor volt input >> directly to output; ie 5vref) or nothing (0volts). this erratic behavior is strange to me, but is that normal for a haywire sensor?

btw - my (S5) temp gauge was at ~1/5th between C and the center (completely warm). not sure if this matters as the voltage continually skipped around.

WAYNE88N/A

Must you argue, lol...Yes, the FSM only gives you a range in some cases, or an "approximate" voltage, and then only at idle or key on (at least for the S4's). That's why I actually recorded readings on my drives to work. I attempted to explain everything in that "ECU" writeup I did...The Reader's Digest condensed version:

1) get to the ECU
2) get a voltmeter, connect the black (neg) lead to one of the studs sticking up in the area. Yes, alligator clips come in damned handy. Connect the red (pos) lead to whichever pin you'd like to check. At this point you'd better have the FSM page for your car that illustrates the pin locations & what component or system happens to be that pin.
3) I use a 1 1/2" or so piece of aircraft safety wire, .032", to shove in the "back door" of the pin. It's big enough to stay in there once I make contact with the pin. A small paper clip might also work. I then connect the red lead via alligator clips to the piece of wire. There, hands-off operation.
4) Depending on what you're reading, and depending on what type of meter you have, set the scale to DC volts (5 volt scale works well for the sensor inputs, 15v scale for almost everything else)
5) Start the car. Let's say you're on the water thermosensor pin. The voltage will be, let's say, around 2v. As the car warms up, the voltage will fall. Nice smooth linear voltages heading down means that the sensor is probably good. .4v is the low end of the scale, in other words, the hottest the engine should get.
6) Drive around with the meter connected as above, stopping to change pins if you wish. Fun items to watch while driving include: AFM, TPS, boost sensor, O2 sensor, water thermosensor, AFM intake air temp sensor, and dynamic chamber (or TB) intake air temp sensor, because the outputs from these little guys vary wildly during driving and having some "fun" with the car.

There, wrote you a damn novel. You happy now???

casio

haha, you wrote more than necessary. pretty much i'm doing what you wrote. i have 22gauge (not sure of width; dont have a digital mic either). i was having trouble getting the wire to stay in, all the while trying to make the pos+ lead stay on the alligator clip. the clip didnt want to cooperate and hold both the voltmeter's lead and the wire into the ecu. thats my only alligator clip (i know, i need to buy some), too.
the voltmeter i'm using i have set to 20v, so i'm good there (i've actually taken 6 weeks, i believe, of automotive electrical, so i'm not _too_ too stupid).
as for driving around, well what can i say but "damn"? i cant believe you actually got your wires and clips to hold and actually drove. hah, i think i'd need to solder (splice) some wires in before i even think about going that far.

and as always, i very much appreciate your help.

i was thinking, though, how different would S4 volts be from S5. and if similar, would an S4 pressure sensor and S5 be compatible?
also, the FSM gives mainly ohms for testing sensors; the voltages i listed were references at the ecu. this is similar, but specific parts are listed in ohms whereas the ecu terminal readout gives a few volt references. kind of weird.

and i understand your input about the ecu's positive/negative issue. its pretty simple in a sense. inputs are positive and outputs (i guess all?) are negatives. when i first read the grounding issue, i was confused. you were referring to -outs- though which, i believe, negates all sensors.

WAYNE88N/A

Lol, OK, couple of things;

When I say alligator clips, I mean the one that can be used as jumper wires, in other words, it's a wire with clips at either end. One end goes on your ECU "insertion" wire, the other goes to the meter lead...

I don't understand your fluctuating voltages (or your negative voltages, for that matter). Are your grounds good? The OEM ones, not all the extra BS you guys like to throw on the car, lol...4.9v is NOT a good thermosensor input, unless yours is different than mine (I wouldn't think so).

What is your 5vref voltage at the ECU? I think you said it was 4.8v, right? That wouldn't affect your thermo sensor, though, because it doesn't receive that 5vref...

Quit worrying about which inputs are positive/negative, just keep that black meter lead on ground the whole time...

Now, if the ONLY sensor that's giving erratic readings is your thermosensor, you may have found your problem. I can't even figure out at this point if you've even got the meter hooked up correctly, or are using a bad ground, though, lol...

Read out everything you can (or want to) at idle, and compare to the FSM specs for idle voltages. Is everything fluctuating???

WAYNE88N/A

Psycho as I am, I reread everything you wrote again. One thing popped in my head- your TPS...What is that bad boy reading at idle, and when you hit that 2500 point?

casio

yea, see, i have ONE alligator clip, not the one with one on each side. the one i have is specially made to ground while the other end goes into the clip for code-checking.

i dont understand the fluctuating (like i said, if thats a normal 'bad sensor' habit, than that makes sense), but the negative voltages may just be the leads backwards on the voltmeter. i was ignoring the negatives, just typed it cause i'm extremely specific about things. i changed where i was grounding, all near the ecu. each choice (all chassis) yielded erratic results.

i'm not sure what youre referring to about the 5vref. are you talking about -out- of the ecu (pin 2I) ? if so, i never checked that specifically. i believe the 4.8 was at the pressure sensor (so i assume between 4.8 and 5.5 at ecu; specsheet shows 4.5-5.5v is normal).

i'm not worrying about the in/out pos+/neg-, just glad to understand it a tad more.

the meter is hooked up. i dont see hwo it could be hooked up incorrectly. if youre getting power readings, its pretty much hooked up right (and if theyre negative, the leads are backwards; no biggie). as far as grounds, i cant say. i dont have a specific "great" ground near the ecu. i used various pieces of metal and saw what their readings were.

i can get volt readings at idle, but i have nothing to compare them to. my engine has to be cold to check water thermosensor (though if it keeps being erratic, then i guess the sensor is wacko). its probably still a bit warm, so i dont know how accurate that would be. the pressure sensor is for 100 mmHg (3.9 inHg) vacuum applied (which i dont have the tool for) or 3.4-3.6v with hose disconnected and plugged. i was going to do this test when i got back out there.
one question; why must the pressure sensor be plugged? if its at barometric when you unplug it, how would leaving it unplugged differ from trapping in the same pressure? i would think it would read bar whether plugged or unplugged.

casio

yea, i mentioned earlier giving the other one a try. i havent done TPS volt tests, but as its hooked to my S-AFC, this should be easy. i want to say its .2v at idle (didnt we go over this in the other thread some days back? ).

oh yea, the problem is semi-intermittent. its very common, but doesnt _always_ hesitate when warm. when cold, its a wall. runs real bad when cold, stumbles, and that 2500rpm wall is nearly unavoidable. almost seems throttle position and/or gear are relevant. its strange. there's so many variables, but the only two i control are rpm and throttle position. though i could also watch my AFM on the SAFC. i need a bar gauge hooked to my car. maybe one that reads off the stock pressure sensor so i can see what that freaking thing is tellin my ecu. you better not be lying, pressure sensor! wish i could tell which students are lying to the teacher. (its a metaphor )

casio

TPS Full Range (i'm 98% sure the safc is hooked to Full Range)
FSM says:
Ign switch ON (idle position): .8v
Ign switch ON (Full throttle): 4.3v
Idle: .8v

Casio says:
Ign switch ON (idle position): .23
Ign switch ON (Full throttle): i didnt test this _just now_, but before i've gotten 4.2v
Idle: .23v

i did, however, rev my engine (neutral) to see where 1v was; coincidentally, it was at 2500rpm.

i guess i could have done this with the engine off, key on, but i revved it while it was still on from testing idle volts.

WAYNE88N/A

It's impossible to keep up with what you're writing, lol...

Hmm, one step at a time...

Yeh, you need a REAL set of jumpers with clips at each end. You already knew that...

What does the meter read when you read out the battery at the posts? I'm trying to figure out if you have a bad meter here, and that's why you're getting fluctuations, or if it's just operator error, lol...

The 5vref is the regulated voltage outputted by the ECU for the sensors- the AFM, TPS, variable resistor, boost sensor, and atmospheric pressure sensor. This also happens to be why all of the aforementioned sensors have nothing greater than about 4.8v inputs to the ECU. But you already knew that...

You're not comparing the idle readings to anything at this point, other than the ranges given in the FSM...Or, I've got readings to compare to, if you so desire...

The book has you disconnect the boost sensor hose because that results in a standard voltage that can be compared to FSM specs (it's the max voltage the sensor should output during normal driving, WOT, on NA's, anyway).

Metaphorically speaking, you CAN see what your boost sensor is doing because of it's voltage inputs at the ECU- you need to know how to interpolate the readings. Same thing for the O2 sensor, also, BTW...

Forgot you had an SAFC, don't know if that changes anything or not...Anyway, check each sensor, one by one, until you find one "bad", or find that they're all good. This is called troubleshooting.

casio

i've tested the battery before (due to problem starting; was a loose terminal). voltage was fine there. good meter. user error? possibly. the fluctuating voltages weren't on me. it wasn't like i tested the same thing different times and got different readings, i sat still reading the same power/ground and watched the voltage go crazy.

yea, i know what "5vref" is, but wasnt sure if you were referring to a particular one (_at_ sensor) or the ECU's main one (which is pin 2I). as said, i never checked this one, but since the pressure sensor was getting 4.8, i assume its all gravy there.

right, i checked FSM idle vs my idle; my off/closed throttle and idle are both ~.57v low (.23 vs .8); my full open is fine.

i still dont understand the difference with the hose/nipple on pressure sensor open versus plugged; both would be full (atmospheric), correct?? i'm not too worried about this as it doesn't help me. just curious.

the safc will help because tomorrow, hopefully, i'll use a couple of the extra sensor wires and hook them up to my pressure sensor and thermosensor. that way i can easily check the readings, whether driving or key on/engine off. it'll just be easier than alligator clips and voltmeter leads.

WAYNE88N/A

Man, don't you think that TPS is a little screwy??? I would say you need to adjust it, but your WOT voltages are in the ballpark. Strange. Try another one , if you have it. And the fact that it's outputting 1v (which should be about throttle closed/idle input) at the same time you're getting the hesitations should be screaming SOMETHING'S WRONG to you, lol...

Don't worry about the boost sensor hose thing, I take all of my readings with the hose on anyway. As long as you have something to compare (like the WOT/hose off FSM numbers) to, it'll be aight.

Hey-do you actually need the TPS connected to run the car? On S4's, she'll run without it, might be something to do for troubleshooting. Don't know how she'll act with the SAFC involved in the equation, though....

casio

i've known that the TPS (low voltage) was screwy, but was concerned about the 2 codes the ECU is actually throwing. as for adjusting, our full-range TPSs dont adjust, only the narrow range portion. and the fact that the 1v happens at 2500, where my hesitation is, doesnt really say much. now dont think i'm an idiot just yet.. i only say this because i see no reason that 1volt at 2500 should be any worse than all the lower voltages between .23 (my lowest) and that 1volt at 2500. furthermore, 1v isnt the (only) correct reference; full range side at idle is .8v; narrow is 1v. now, if the ecu only looks at narrow, yea, then its coincidental. still, why would 1v at 2500 be worse than lower volts at lower rpm if they're just as incorrect??

i've read we can run without the TPS. i read awhile back that, to test the TPS (one ghetto way), you let the car idle, unplug the TPS, and if the car's idle stays the same, the TPS is (likely) bad. i prefer a better technique, though this may well be perfectly fine. i really dont know. it makes some sense, though.

as for the SAFC, i'm not sure. i dont know if it needs to know the throttle position or not. i know i have mine hooked up to the AFM intercepting its voltage (whereas some people intercept the TPS and some the Pressure Sensor). if it did make a big deal, i could unhook the SAFC from the AFM wires and plug em back together.

WAYNE88N/A

Ahhh, even though you said "full range", and I read "full range", I still pictured the "narrow" range in my head, because I figured you must have been talking about that one. My bad...

At this point, unplugging the TPS might be the easiest way to troubleshoot this. It might at least tell you if it is in fact the TPS. Will the S5 MOPs still work OK with it disconnected?

I don't know anything about what you can do as far as the SAFC goes, never had to deal with that animal...

If you're worried about the codes more than the TPS, the first thing I would check would be the thermosensor, visually and electrically...But that's me...

casio

no prob, i know you have an S4, i'm the same way. in order to avoid my sociological theories, i'll just say its normal to accept what you know.

i'm already getting the bogus signal from the TPS, though i dont know how much exactly that throws off my fuel/timing/tuning. nor would i see why this would affect it when cold vs warm. but everything that makes an improvement is good for something.
MOP?? who cares! i premix. i honestly dont know what sensor(s) the ecu looks at to signal the MOP.

the SAFC has a few extra perks. having wires spliced into the ecu harness and seeing what voltage the ecu sees (or should be seeing) is a plus for obvious reasons.

i'm not really worried about the codes more than the tps, per se, it was just that they're more "in your face." i would think something like the tps would throw a code, but maybe not. i'll say i'm most worried about whatever is making my car run worse.
you seem to bring up the thermosensor a lot. this continually puzzles me. i dont know how much tuning is different for a cold engine, but i'm more concerned with how my car runs when warm (for now at least). the ecu, when in fail-safe mode, reads 176degrees for the thermosensor. this seems reasonable when the engine is in fact warm.

i need to get some real-time pressure sensor voltages and test and/or swap that tps. i'll re-bump this thread when i get those done. i more than appreciate your input. i dont know why my threads get so few posts. maybe i've made too many enemies or ticked off enough people..

WAYNE88N/A

Sociological theories? Lol...

TPS should throw a code when it loses signal (been there, done that on that one, too) but you won't be noticing it due to the bucking going on, lol...

The main reason I keep trying to get you to verify the thermosensor one way or the other is because I've been there on that one too. Long, long time ago I cracked the sensor backshell with that damn alternator nut (with the locking tab/ harness standoff on the nut, to be more precise) while tightening the big bolt at the bottom. Don't know if S5's have this feature or not. Anywhose, it was a hairline crack, not very visable, but the contacts inside would seperate when the engine got hot. Driving down the road all hunky-dory, and all of a sudden she would just lose power for a couple of seconds, like a limp-home thing, then all back to normal again. Another symptom was that she would crank for about 5 seconds more than usual before she would start. This was in the days before my LED code lights, so you can imagine how long it took me to finally find the problem.

So, lets say your thermosensor or wiring is bad. The ecu will default to the 176*F setting, which means when she's cold, that guy is going to be telling the ECU that she's hot, while all of the other sensors are going to be telling it she's cold. Talk about screwing with the ECU's head, lol.

Ha, we're from Texas...That's enough right there to get people pissed off at ya...You know, jealousy

casio

i found the water thermosensor. i'd seen it before, just didnt know what it was.
okay, i tested it, again, and again got a few erratic voltages and then paused at 4.99v. i started the car and did the 'idle when cold test.' youre supposed to see .4-1.8v; i saw a straight 4.99v. i can only assume that the sensor provides a resistance, so when its messed up, it closes the circuit completely.

i tested the pressure sensor again. the one volt reference the FSM gives it checked out fine. it says 3.4-3.6; i got 3.4. i didnt bother taking the vacuum line off or plugging it, i just tested. i figured if the volts were off, then i would do that. i got 3.4v, so i considered that test passed.
btw: i did this test at the sensor. (heh, i know.... )

now for the TPS. i ohm-tested the one on the car and the extra one. thinking about it more, i think it should be on the car to test accurately. it may not be as out of spec as i thought. as for the one on the car, it was near proper spec, but not quite. i left the numbers in the car, but i'll post them later. neverminding those numbers, i did find something interesting. the TPS (i dont recall if it was narrow, full range, or both) had kind of a dip in it. in the high 3 range, after being linear, the ohms would go back the other way, then continue the proper way again.

thermosensor: needs to be replaced (but damn its hard to get to!)
pressure sensor: seems fine, but may replace to see if it gets rid of the code.
tps: seems to have a bad spot; i dont know what causes this, but it may need to be replaced.

Kenteth

I just wanted to say I pulled a code 13 today and new it would be hell to find info on it. You guys have alot of helpful info here!