Jersey Posted August 14, 2003 Share Posted August 14, 2003 Hey all. Ok, first an update on my sudden rich idle condition for all that have read/replied in my other post. Ripped it all apart AGAIN last night, AFM, boot, I.C. pipes...etc..and checked all sensor values AGAIN and this is what i found out - nothing is wrong with any of it! So....i checked my meter against my buddies Fluke. Guess what...my POS meter was out of calibration! ah ha! So, i started re-checking all the ohms/voltages on all the sensors AGAIN and the O2 is NOT reading in spec. At idle after warmed up, it shows about 280ohms. Running it @ 2000rpm for at least 4 minutes, it goes up to about .410 and that's about it. Snap the throttle plate closed - it jumps back down to .1 and then levels off around .340. No wonder the little green light on the ECM never flashed after running it @ 2K for over 4 minutes - it never broke the .45 threshold! UG. Anyway, i picked up a new O2 today and will install it tonight. Lesson learned...check your meter every now and then! Ok, so here's why i posted this topic - i'm looking gain some more knowledge on these sensors. Some of you may know me but for others, I'm basically trying to stretch the most out of a stock L28ET and it's components. The crazy reasoning behind this? MONEY Married/2 children, this is a "toy" as wife refers to it and does not exactly enjoy consistently spending lots of cash on, new house = bigger mortgage and taxes suck....blahblah...i'm sure you get the idea. I also think you can get the L28ET to really perform with little tweaks here and there without breaking the bank and i enjoy trying as long as i get the darn time! ha. All in question are referring to a L28ET which some components/values may differ from the N/A ZX's. I'm pretty sure the ECM adjusts the air/fuel mixture relative to the values returned from ALL these sensors basically by adjusting injector pulse width - the duration the injector stays open and sprays. And that's basically my question - do all these sensors, by means of the ECM, effect injector width? Please correct me on anything i post here as i'm always willing to learn and if you have any other information on any of these components and/or if they do more than effect just the injector, please, share at will! 1 - ATS (Air Temp Sensor) - mounted inside AFM - increases or decreases resistance relative to air temp. 2 - AFM (Air Flow Meter) - It has an initial resistance value (i believe for the ET's it's suppose to be 280-400ohm) This initial resistance value also has an effect on the full sweep values of the flapper. 3 - HTS (Head Temp Sensor) - increases or decreases resistance relative to cylinder head temp. 4 - O2 (Oxygen Sensor) - increases or decreases resistance relative to oxygen measured in downpipe. 5 - TPS (Throttle Position Sensor) - Connected to the throttle plate and has idle, off idle and WOT contacts. It sounds (by ear) as if this sensor actually controls injector pulse speed when changing from idle to off idle contact, but not sure. 6 - Another question on the TPS - there is a 3rd WOT contact that is unused on the ET. Why? Is there a way we can use this contact when we are at WOT, stretching every gear down the track, to throw more fuel at the increased boosted air? Sorry for being rhetorical in any of the information i asked because i'm sure it's all somewhere in the archives but, if you have a minute and know some or all of the answers, i'd appreciate it. Thanks. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 14, 2003 Share Posted August 14, 2003 I hear you Jersey, on the money thing. I have 2 young kids too, and a very limited budget. Interesting on the O2 sensor and how your meter was so far off. But that's one sensor that will die on you, no surprise. The rest of them are very durable, I haven't lost any yet. Of course the air temperature sensor bears on the injector pulse width, but I can't say whether it affects the WOT maps or not, but certainly in closed-loop calculations and trim. Personally I can't stand the stupid flapper AFM, and that's why I got rid of it with a Z31 ECU conversion. The TPS of course is for idle. With zero load, throttle closed, it is indicating to the ECU to run the motor lean for best emissions, and I believe that is not closed loop; runs off a programmed map. So when you come off idle, it switches modes to cruising, and uses the O2 sensor to balance the mixture. There is no input to the turbo ECU to indicate WOT, and that's why you can't hook it up. I'm sure there is a ghetto rig possible, but the ECU just seems to know when you are WOT, and it fuels properly. I don't see a need for it personally. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted August 15, 2003 Share Posted August 15, 2003 I have that sensor info in the FSM. I'll look it up when I get a chance. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 15, 2003 Share Posted August 15, 2003 Glad to hear you found a foothold with this problem, I've been wondering what's been going on with your car. It's also a great thing that you posted this right now... I was just about to post a question about exactly what the TPS does, as I keep going back and forth between having it connected and disconnected... obviously it doens't seem to have much effect on the way the car drives, I notice the idle will fluctuate one way or the other whenever I mess with it. So my question is this, what would the EXACT effects be if I drive with it disconnected? It will just run a bit richer at idle? Super plug fouling rich or just bad for emissions rich? Will it affect the drivability of the car at all? I swear it feels better disconnected, even though logic says it does/should only affect idle. I too noticed that the turbo TPS doens't have the third pin for WOT position. Think I better replace the O2 soon also... Jersey did you buy one from regular auto parts store or from nissan dealership, and how much was it? Quote Link to comment Share on other sites More sharing options...
Bernardd Posted August 15, 2003 Share Posted August 15, 2003 Married/2 children, this is a "toy" as wife refers to it and does not exactly enjoy consistently spending lots of cash on, new house = bigger mortgage and taxes suck....blahblah...i'm sure you get the idea. I also think you can get the L28ET to really perform with little tweaks here and there without breaking the bank and i enjoy trying as long as i get the darn time! ha. Nice to hear other people have the same budget minded approach as I do. On to your questions. The air temp and Afm combine to tell the ecu the mass of the air being ingested. Same thing as the maf on the z31 eccs only rudimentary. Hts provides an enrichment to engine when cold. The lower the resistance the higher coolant temp= less fuel. I installed a switch to add 5k resistor to the circuit at wot. Didn't notice any increased power. o2 sends a voltage to the ecu telling it to correct for a 14.7 afr. If you disconnect it completely the car should run fine. Or get a new one. Tps tells ecu the car is off idle. SleeperZ is correct in that it's a table (at least in the z31ecu it is) The reason for the 3rd terminal is that's the way bosch makes 'em. In later model Nissans the tps is used as a tranny control input. The ecu combines the afm and rpm for determining engine load. At about 4500rpm the afm is fully open and the ecu uses rpm only. Inside the afm is a small circuit with enrichment resistors. You can easily customise acceleration enrichments by changing the values. I've chosen to use the z31 ecu along with an eprom burner to make my own custom maps for larger injectors. So far everything has cost around 200 dollars canadian.(not counting injectors) Cheaper yet would be bypassing air around the afm and/or tampering with the spring (inside afm) is no cost at all, when using larger injectors. Hope that helps, Bernard Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 15, 2003 Author Share Posted August 15, 2003 Hey guys, thanks for the replies. I changed the O2 last night and it didn't help. It does give much better readings - .4v @ idle, .9v running @ 2k rpm for 5 minutes, but it still runs rich as heck at idle and the LED on the ECM still won't blink, EVER. It does light when i turn the key into the ON position so i know it's not just blown out. Hey, i'm trying to think of everything So then i start digging around again last night until about 2am and still haven't figured it out. Unreal. What gets me now is the Head Temp Sensor readings. With the sensor unplugged, key in the run position, i'm getting 5 volts on the yellow/green. The resistance across the head temp sensor is right in the curve as per the FSM at all different temps so it is working properly. Just for argument sake, the water temp is at about 110 and the resistance across the head temp sensor at this temp is right about 1.1k ohms. When i connect the plug back into the sensor, i now get a 2.4v reading on the yellow/green wire and a .02v on the black? Then i cut the black wire off of the back of the head temp sensor and measured both again, still plugged in - now it's back to the 5v on the yellow/green and it also shows 5v on the black! Then, I traced and ohmed out both wires back to the ECM to make sure neither weren't shorted to ground or each other, which they both tested fine. I also ohmed out both pins from the HTS to the head to make sure it was not grounded internally, and it wasn't. Does this sound right? In the FSM, it seems to only list what the value of the resister should be at, at certain coolant temps, not what the voltages in or out should be at certain temps. At least i can't find it in there. Also in the AFM, the air temp sensor inside the AFM shares the same curve as the HTS so, i checked that just for the heck of it. Maybe it would explain how the HTS circuit should work, i thought, anyway. With the harness plugged into the AFM, one wire on the ATS had 8v on it (figuring in) and (at the time, whatever air temp it was reading) 5v on the other wire (figuring return value) Then i put both legs of my meter on each of the pins and it gave me the 3v - the voltage drop across the resistor. Fine, that seems to measure correctly. I would think the HTS would be somewhat the same....something like 5v in through the yell/green, across the variable resistor, and back to the ECM with the new lower value, like 2-3v. Not on mine and maybe this is just how it works. i don't know. I also took off all connections, cleaned them all with a dremmel/wire brush, ran ground legs all over the car and none of it helped. One thing i did find strange, if i pull the vacuum line off of the FPR and plug the hole in the intake, she runs exactly the same. I thought at idle, if i did this, the FPR diaphram would drop, clamp off most of the return line and drown her in fuel? I checked fuel pressure last night and @ idle (gauge between filter and fuel rail) and it reads perfect - 38psi. Makes no sense but i'm all out of sense with this rich idle problem now anyway! If anyone has any suggestions or has ever read voltage in thier HTS, please, post away Thanks so much for all the info on the sensors and info you supplied guys. Helps me understand how the whole system works in conjuntion with each other better. I'm also glad i'm not the only "older 35 yr old" married with children guy here and can share my pain Actually, my wife has really been great about it all. Never know what next month will bring 525 - i went to Pep boys and picked the O2 up - made by bosch, $20 for the one without the male end and $30 with it. Thanks again guys. Quote Link to comment Share on other sites More sharing options...
mobythevan Posted August 15, 2003 Share Posted August 15, 2003 My completely stock setup with fuel pressure gauge between the filter and fuel rail reads 30psi at idle. It reads more like 38psi if I pull the vacuum line off the FPR. Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 15, 2003 Author Share Posted August 15, 2003 ut oh. Why do i have a 36-38psi @ idle as being the correct # in my head? And i just went right by this after i checked because i thought that was what it was suppose to be??? Maybe i'm thinking of my old '77 280? If it's suppose to be around 30 with 18-21hg vac @ idle, then the 38psi i'm getting is probably, hopefully, causing my problem! And when i checked the pressure, i did it twice with the return line hooked up and then again with a hose going into a open tank just to make sure the 5/16" return line wasn't too small for the high pressure Walbro pump or if it was clogged or something. It didn't change the pressuse either way and i blew the return line out just to make sure it was clean anyway. So, if it is suppose to be 30 and i'm at 38, then basically the only "logical" thing left is the FPR. When i pulled the vac line off of the FPR and it did nothing to the idle (stayed rich and no change in idle) i put 20hg's of vacuum on it and it did hold, but it also didn't effect idle/rich problem. Wonder if it's just stuck closed? I also thought this may be the problem and did tap it a few times when i had the 20hg's on it but it didn't make any difference and i just figured that it all must be right and fuel pressure was right @ idle anyway (so i thought) so figured all was fine. hmmm. Now i need to go home and re-read the FSM and re-check that pressure. Moby, thanks a bunch. If this is it, i'll owe ya one. Quote Link to comment Share on other sites More sharing options...
BayAreaZT Posted August 15, 2003 Share Posted August 15, 2003 According to the service manual 30psi at idle and 37psi the moment accelerator is depressed. Hope this is the answer to your problem. Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 15, 2003 Share Posted August 15, 2003 I guess I run rich at idle, I run 43.5 psi at ALL times, didnt think it would matter too much. All I really care about is my mpg and my Boost power. I do get a rock solid 22hg doing so with 850rpm. Very strange issue Jersey, very strange. Im out of ideas, sorry bro. Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 16, 2003 Share Posted August 16, 2003 I still wonder if a screwed FPR could be the cause of my problem too? Already almost every problem I've had has also been happening to at least one other person, and their fix usually worked for me... and same as Jersey here I've gone thru and checked and double checked almost eveyrthing and am really running out of options... that FPR was about the only thing I dont really have a way to check. Should the car run differently at idle if I pull off and plug the vacuum line that goes to it?? Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 16, 2003 Share Posted August 16, 2003 I guess I run rich at idle' date=' I run 43.5 psi at ALL times, didnt think it would matter too much. All I really care about is my mpg and my Boost power. I do get a rock solid 22hg doing so with 850rpm. Very strange issue Jersey, very strange. Im out of ideas, sorry bro.[/quote'] Are you saying you have no boost reference on your FPR? That can be hard to tune out. Especially under boost. Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 16, 2003 Author Share Posted August 16, 2003 Man, i am hoping Dale. Home now. I put the gauge in line, between the filter and hard line and yup, 38lbs @ idle. Vac gauge showing 20hg. If i pull the vacuum reference off of the FPR, the pressure jumps up to something like 45lbs. 327 - aren't you running 370 injectors? I would think 43.5 @ idle, it would be rich. Ever check what voltage your O2 is sending? Damn, if your Z is basically built like mine and you have a rock solid idle with 43.5lbs @ 850rpm, i guess getting this thing down to 30lb @ 20hg isn't going to solve my problem. I wish my buddy would show up with my vacuum pump! He's on his way and if i can manually get the pressure down by applying more vacuum than 20hg to the FPR, we'll see if it does the trick. Hoping so. 525 - here's a cheap way to check your pressure. Go to a Home Depot, or whatever you have near you and pick up a 0-100lb gauge ($10), then go get a couple of brass fittings ($1) for your fuel lines to hook to and have some teflon tape ($1) so it wont leak when you put it all together. If you dont have any small clamps, that'll cost maybe another $1. All in all, it shouldn't all cost more than $15 and you will always know what your pressure is. Me, on the other hand had all this and didn't want to permanently install it and THOUGHT it was suppose to 36-38lbs @ idle. DUH. We'll see soon if this was my problem.... Quote Link to comment Share on other sites More sharing options...
Guest bastaad525 Posted August 16, 2003 Share Posted August 16, 2003 awesome thanks for the tip!! Will probably do this tommorow if I have time and see what my fuel pressure is at too... will go a long way towards easing my mind to find out one way or the other if everything is okay there. What I'd really like to do is get one of those in-car units so I could see what it's doing when my car starts acting all funky when I get on it... but for now I think I'm gonna have to stick with the $15 method... thanks for the tip again Jersey Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 16, 2003 Share Posted August 16, 2003 I guess I run rich at idle' date=' I run 43.5 psi at ALL times, didnt think it would matter too much. All I really care about is my mpg and my Boost power. I do get a rock solid 22hg doing so with 850rpm. Very strange issue Jersey, very strange. Im out of ideas, sorry bro.[/quote'] Are you saying you have no boost reference on your FPR? That can be hard to tune out. Especially under boost. Oh no, I do have a boost reference as well. Oh heck no I wouldnt run a fpr without a boost reference, that crazy. I like the response at 43.5psi a lot more. Quote Link to comment Share on other sites More sharing options...
fl327 Posted August 16, 2003 Share Posted August 16, 2003 Hey Jersey. Your power is still good right? Car drivable? Im in awe as to why your car is running funny, sorry to say. I can think of absolutely nothing after reading your posts here and on zcar.com. If I could check it out in person, might be different issue. Im thinking about the 370cc swap though- Ive have just never been a big fan of playing with the AFM, I have a couple spares I might tinker with though. I like running 43.5 psi because the car is little faster to respond when I run it like this. If I ran 370cc I would run a little lower fuel pressure, maybe 34-35 or so, have to see how lean of an idle I could get with the AFM tweaking alone before playing with the fp, or vice versa. Im stumped Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 16, 2003 Author Share Posted August 16, 2003 I AM STUMPED AS WELL 327! Power is good and yes, driveable, but i know something is wrong because she just stopped idling correctly one day out of the blue and is running real rich down low. I cannot believe this is getting the best of me. I has to be something stupid. Ok, newest update, as of 2:30am last night - So i get my vacuum pump and try to pull the pressure down close to 30psi. With as much vacuum i can apply to the FPR, the lowest i can get it is around 32-33psi and guess what, no change at all! Unreal. I let all vacuum go to the FPR, pressure rises to 42-43 and still no real change in idle - still rich as a pig. Mind you, this is all with one port of the intake manifold uncapped, only because she'd crap out after a minute of idle due to running super, super rich (burning eye syndrome) Ok, so THAT'S NOT IT. I then start playing around with everything AGAIN and just for kicks, decide to re-check timing. Yep, dead on 20deg BTC. Then checked to see what she advances too...NOTHING. I get no advance, actually no movement at all...just a steady 20deg BTC ALL THE TIME. Rev it up, idle drops below 800 when throttle slapped closed..still 20degrees. HUH? I figured maybe it runs at a default value of 20deg until it's warmed up (closed or open loop mode) and made sure it was up to normal operating temp and it still didn't change..always 20BTC. It's just one thing after another right now. I don't get it. Must have stepped in the wrong Now i'm thinking ECM again, but i'm still not convinced that's it. I'm really betting it's something simple. That's usually how it is when i run into this much trouble with something..like a ground or something! Anyway, that's where i'm at now. Guess i need to make a new post about '82ZXT dizzy and Crank Angle Sensor operation to figure out what could possibly be the reason it's not advancing. Maybe THIS is causing all my issues. Man, i wish this on noboby. If any of you guys following my dilemma have any info on the CAS other than what the FSM says, please post it. Guys, thanks a lot for all the help and time you've taken to think and post about what could possibly be wrong. I will not give up. Thanks again. The saga continues.... Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 16, 2003 Share Posted August 16, 2003 Jersey, you have a bad pressure regulator. If it's not 38 or so psi with the reference removed, it's bad. And it will cause it to run rich at idle, I know, because I had one do that on me. Caused me to fail an emissions test, and it ran poorly too. Quote Link to comment Share on other sites More sharing options...
Jersey Posted August 16, 2003 Author Share Posted August 16, 2003 Nathan - i did pull the FPR diaphram up enough with about 30hg vacuum to get the pressure down to about 32psi but it never ran better, still rich as heck. Maybe my pressuse is a little high due to the Walbro pump i have in. That's the way i'm writing fuel pressure off right now anyway since i found this NEW problem - TIMING. I'm going to start troubleshooting in that direction to see what i come up with . Thanks a bunch for the suggestion. Quote Link to comment Share on other sites More sharing options...
SleeperZ Posted August 16, 2003 Share Posted August 16, 2003 It should be possible for a higher flowing pump to overwhelm a stock regulator, especially at idle. If you can monitor fuel pressure while driving, you can confirm that problem by checking the pressure goes down under moderate loads, or verifying once under boost that your pressure is 37 psi plus your boost pressure. Quote Link to comment Share on other sites More sharing options...
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