Forums/Z31P/z31-repairs-forums engine-mechanical/85T Bad Hesitation/Hiccup/Misfire
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JLaraZ31: (2017-08-22 00:50:07)
So recently I've been having this problem, I've looked into and searched others with similar problems to try and find a solution. At first I thought it was the CAS because it threw that code. Upon replacement, the code went away but I still had the same problem, checked codes and founs for CHTS, ended up being the wire coming undone from the harness.
After that I also adjusted the AFM with guidance from the fuel service manual to get it to where it needs to be; I also checked for vacuum leaks but couldn't find any. It ran better but still had the issue. Replaced the sparkplugs as They were pretty fouled and looked like they needed to be replaced. Ran much better and only hesitated bery lightly but was still hesitating.
At on point it didn't want to hit boost as I went through the RPM almost as if it was in limp mode. Whenever I revved it in idle it would black smoke but I dont have any codes except for idle switch which I've had for a while causing a high idle.
I do have an intercooler as far as mods go, I'll check distributor timing tomorrow and double check for any vacuum leaks or loose connections in the couplers.
any input would greatly appreciated
JLaraZ31: (2017-08-22 13:40:23)
So I went to check the distributor timing and vavuum leaks (haven't checked intercooloer set up yet)and didnt find anything wrong, took for a test drive and it still acted up. When I got back went to pull the ecu for any codes and when I went to turn the key it didn't light up. I tried another ecu that I have to see if it did the same but it wasn't getting any lights either.
if any one could help guide me in finding where the power source goes for the ecu that would be appreciated as well.
JLaraZ31: (2017-08-23 13:26:31)
Was a blown fuse, got it to run again. Still having the same issue though. Will check CHTS again as well.
JLaraZ31: (2017-08-24 12:55:11)
So after checking a few small things I started driving it around town and it didn't to do it as much when it was at ooerating temperatures. Sometimes it would do it but it would be for about a 1/4 mile and than be normal. After having left the store to go home it didn't do anything out of the ordinary at all except for one time when getting off on a light and the engine temp was roughly a quarter on the gauge.Any input on that?
JLaraZ31: (2017-08-25 12:29:54)
Went to read to spark plugs (3 days old) and they are blacks than charcoal. I know the CHTS is good so I'm leaning towards the waiting right now. I'll check that out later today.
JLaraZ31: (2017-08-25 14:44:55)
Well the CHTS wiring is good, still having that issue. Will pull the intercooler piping today and inspect to make sure everything is tight amd sealed.
JLaraZ31: (2017-08-26 01:20:45)
Double checked my intercooler piping and everything was fine but still checked everything. I also double checked theAFM calibration to make sure it wasn't too rich or lean. I changed one plug wire and it almost didn't act up until I got home from the store but it wasn't as terrible as it was before. I'm going to replace the rest ou'd them and see if that fixes it. Looks like it may be the plug wires. Whenever I can I will update on it.
FrozenZ: (2017-08-27 12:04:10)
If your plugs say that you are running crazy rich there's two other things worth checking, the TPS and the O2 sensor. The old school wisdom was that the O2 sensor didn't do anything outside of "cruise" but I found that when I had an otherwise perfectly running turbo motor, without the O2 sensor the car had serious driveability issues. It's probably worth replacing.
If the TPS is set wrong, or failing intermittently and giving weird readings, the fuel pump could be kicking in and out when it shouldn't.
JLaraZ31: (2017-08-27 15:42:44)
If your plugs say that you are running crazy rich there's two other things worth checking, the TPS and the O2 sensor. The old school wisdom was that the O2 sensor didn't do anything outside of "cruise" but I found that when I had an otherwise perfectly running turbo motor, without the O2 sensor the car had serious driveability issues. It's probably worth replacing.
If the TPS is set wrong, or failing intermittently and giving weird readings, the fuel pump could be kicking in and out when it shouldn't.
I'll double check the TPS again as well as the O2 sensor. But wouldn't the O2 sensor not allow me to check AFM calibration in that setting if it was bad? Just curious as i am still learning about the z31.
NissanXRMA: (2017-08-27 18:20:34)
How old if your dizzy cap and rotor? Are they OEM?
JLaraZ31: (2017-08-27 23:48:46)
How old if your dizzy cap and rotor? Are they OEM?
No, the PO replaced them a few months before I bought it as well as the CAS. I'm also using the PRW2 Power transistor and have recently replaced the ignition coil a month ago.
FrozenZ: (2017-08-28 10:36:09)
I'll double check the TPS again as well as the O2 sensor. But wouldn't the O2 sensor not allow me to check AFM calibration in that setting if it was bad? Just curious as i am still learning about the z31.
Only time I ever calibrated my AFR was with a brand new O2 sensor so I can't say what happens if you try it with a funky one. The ECCS will happily accept non-sane inputs like -50C fuel temps and try to work with them, so I'm not sure how far I trust its diagnostics.
JLaraZ31: (2017-08-28 14:14:25)
Only time I ever calibrated my AFR was with a brand new O2 sensor so I can't say what happens if you try it with a funky one. The ECCS will happily accept non-sane inputs like -50C fuel temps and try to work with them, so I'm not sure how far I trust its diagnostics.
Hmm good to know. I'll look into my O2 whenever i have the chance.
also, while I'm waiting to get my plug wires i bandaged mine with electric tape and have only had a slight stutter on cold start after 2nd gear.
JLaraZ31: (2017-08-30 11:49:26)
Update: I got installed new plug wires and it only hesitates at cold start for 2 gears. I'm wondering if maybe I didn't properly install one of them fully (cylinder 4 was the hardest for me) but after that it doesn't come back anymore. Thoughts?
Z_Karma: (2017-08-30 17:36:12)
Also could be ECU related.
My 84T runs fantastic, no problems, passes emissions and is reliable.
However, if i try to drive off on a cold start without letting it idle for a minute or so, it'll buck and stutter and maybe backfire if i don't let off or feather the pedal.
The earlier ECU's had a problem with lean surge when they're cold. IIRC, there was a known issue and a second module was added into the harness and mounted
beneath the battery tray, although i cannot find the TSB that mentions this. Mine has this module and still has issues with cold starts.
There was also an oldschool fix by switching the CHTS signal to the FTS
Some info is still archived in various forum threads like this but a lot is not easy to find anymore.
Over the years on here and other forums, I've pretty much surmised that the best remedy for this cold start/lean surge issue is to convert what is required to run a later model ECU.
This may or may not be related to what issues you are encountering but it could be related.
JLaraZ31: (2017-08-30 20:03:39)
Also could be ECU related.
My 84T runs fantastic, no problems, passes emissions and is reliable.
However, if i try to drive off on a cold start without letting it idle for a minute or so, it'll buck and stutter and maybe backfire if i don't let off or feather the pedal.
The earlier ECU's had a problem with lean surge when they're cold. IIRC, there was a known issue and a second module was added into the harness and mounted
beneath the battery tray, although i cannot find the TSB that mentions this. Mine has this module and still has issues with cold starts.
There was also an oldschool fix by switching the CHTS signal to the FTS
Some info is still archived in various forum threads like this but a lot is not easy to find anymore.
Over the years on here and other forums, I've pretty much surmised that the best remedy for this cold start/lean surge issue is to convert what is required to run a later model ECU.
This may or may not be related to what issues you are encountering but it could be related.
I appreciate that, what year do you recommend? 87 88?
Also checked my codes and have 21 and 31. Confusing me how they came up.
JLaraZ31: (2017-08-31 02:56:47)
Quick update: Today after work it started acting up again even at operating temps and would struggle to accelerate. But as I was arriving home it acted just fine. Could the codes have something to do with this or could it be something else? afm?
acted perfectly normal today with only a sputter once in 4th. Although I did find a two wires touching those from the CAS on the passenger side head and moved them out of the way. Maybe that caused something? Beats me.
Z_Karma: (2017-08-31 21:03:55)
Intermittent issues of any sort are a pain in the ass to troubleshoot, but you do learn a lot. You should find out what those wires are in the diagram (GOT FSM).
As far as recommended ECU, Read here.
Xenons site has tons of great information.
JLaraZ31: (2017-09-01 11:05:12)
Intermittent issues of any sort are a pain in the ass to troubleshoot, but you do learn a lot. You should find out what those wires are in the diagram (GOT FSM).
As far as recommended ECU, Read here.
Xenons site has tons of great information.
Yes, I do have the FSM as well as a Haynes manual (haven't sat down to look at both for the differences). I looked up to what stray wires went and they were for the air regulator. Still in the engine just not hooked up.
I appreciate that very much, because of school I'm not going to have as much time with it but I will do what i can to keep updated on.
JLaraZ31: (2017-09-02 22:28:41)
So I went and bought a multimeter and tested my chts (both my spare and current one) and both are working fine. Because of my code 21 I am going to test the transistor and CAS to be safe. Is the prw2 a pnp or npn? Anything else i should test for?
JLaraZ31: (2017-09-03 15:17:45)
So, folowing the FSM and everything you guys have told me to check I am stumped. O2 is good, ignition coil is good, CAS is good, transistor only differs by almost 1 volt, and afm is good. Checked my plugs and they're black and smell of gas. I'm almost out of ideas but will check and see everything else one more time.
FrozenZ: (2017-09-04 11:50:57)
Uhhh… hmm. Have you got a fuel pressure tester? Check and make sure your FPR responds to changes in vacuum… you can just pull the vacuum line and that'll tell you if your FPR is doing something, but it would be better to actually check the fuel pressure.
JLaraZ31: (2017-09-06 01:06:26)
So, Im gonna go ahead and say i have no idea what i did when testing everything, but she runs perfectly, no surges at cold or operating temps, all codes cleared, everything perfect. 1st I thought it was just acting right as it did before the issues, but she's not giving me problems or issues. I guess make sure everything is reading right? I've no idea right now.
JLaraZ31: (2017-09-11 15:17:30)
So update after a week: it's been running good; however every so often I will get the symptoms again but more controllable than it was before and it's very short. Checked codes and I have AFM, CAS, and Load signal. Any input on these codes? I'll test them when i get out of classes.
JLaraZ31: (2017-09-17 14:47:11)
So after looking things up thanks to Z_Karma's link I found out my ECU is from an 86 NA. For the 6 months I've had the car it never gave me any issue until this one. would it cause any issues using an NA ecu on a turbo engine not counting my current situation? Should i try a turbo ecu from an 84/5/6/7?
JLaraZ31: (2017-09-19 00:23:11)
I keep checking the codes as it will run perfectly fine with no issues and suddenly it will black smoke like a diesel and not want to accelerate, but once it can it will accelerate like there was never an issue until I get within lower RPM ranges. Only codes I have are 13, 21, and 31, after reading the FSM 21 could be from fouled out plugs from how rich it has been running, but 13 still eludes me. I'm assuming that 31 is with 13 as the first time it has acted like this was when I got the car in february and it turned out to be the wire for the CHTS being outside of its pin. I've checked the CHTS and the CHTS subharness as far as readings go and, when disconnected from the ECCS, reads what the CHTS is showing (which is within working range as far as the FSM says), but when connected to the ECCS it reads somewhat lower than what the CHTS does. Is that normal or is my ECU gone? Also I've inspected the CHTS subharness closely and saw that it has some damage to it could this be my issue or would it not matter as much since the proper reading from the CHTS is going to the ECU pinouts?
FrozenZ: (2017-09-19 12:00:42)
Stop trying to troubleshoot other things until you put a turbo ECU in the car. The main thing that's wrong is that your injectors are, like, 50 per cent larger than the ECU believes they are and the fuel and timing maps are different.
JLaraZ31: (2017-09-19 12:32:40)
Stop trying to troubleshoot other things until you put a turbo ECU in the car. The main thing that's wrong is that your injectors are, like, 30 per cent smaller than the ECU believes they are and the fuel and timing maps are different.
It will be awhile before i can get a turbo ECU for it. Are there pinout differences between the ecus?
GodofRichy: (2017-09-19 17:21:26)
Although I'm not sure about the pinout differences, everyone is right about the ecu. NAs came with 180cc injectors while Turbos came with 260cc injectors. The fuel pressure for both are the same, so you have a Non turbo ECU which continues to foul the plugs since the injectors are 80cc bigger than what its programmed for. Rockauto has remanufactured ECUs, but I've never personally ran one. Also here's a website you should get familiar with.
Rockauto(Parts distributor)
http://www.rockauto.com/en/catalog/n…computer),2896
RedZ31(Jason's site that has a ton of information about our cars)
JLaraZ31: (2017-09-19 18:30:39)
Although I'm not sure about the pinout differences, everyone is right about the ecu. NAs came with 180cc injectors while Turbos came with 260cc injectors. The fuel pressure for both are the same, so you have a Non turbo ECU which continues to foul the plugs since the injectors are 80cc bigger than what its programmed for. Rockauto has remanufactured ECUs, but I've never personally ran one. Also here's a website you should get familiar with.
Rockauto(Parts distributor)
http://www.rockauto.com/en/catalog/n…computer),2896
RedZ31(Jason's site that has a ton of information about our cars)
Reading into the information about ECUs I saw it mentioned the desirable unit for 84/5 turbo is the 88/9 NA ecu; however wouldn't that still be somewhat similar to the 86NA as far as injector sizes go?
I appreciate all the helpyou guys are giving me greatly.
FrozenZ: (2017-09-19 18:57:40)
That's only if you are going to go with a Nistune system. You can probably find an 84-5 turbo ECU on here. Tbh I have heard of enough bad ECUs lately that I would probably go with one of the reman ones from rockauto and get the 1-year warranty.
JLaraZ31: (2017-09-19 20:16:06)
That's only if you are going to go with a Nistune system. You can probably find an 84-5 turbo ECU on here. Tbh I have heard of enough bad ECUs lately that I would probably go with one of the reman ones from rockauto and get the 1-year warranty.
I'll try to look and see if there are any on here, thank you. My brother had found an 86 turbo that he's going to take the ecu out of and send to me. I know I may need to change the O2 sensor to be compatible with it but with it being side feed would it affect anything that I'd need to make changes off or best stick with the 85T ecu?
FrozenZ: (2017-09-20 01:36:17)
86T ECU should drive 85 injectors but I can't speak from experience.
https://dev.z31library.com/xenonzcar_archive/z31/modelse…ral+Turbo+5spd
I have an 84T 5spd ECU I could sell you but a) it hasn't driven a car in at least two years; and b) I'm in Canada so shipping's gonna be a lot more. PM me if nobody else comes through.
JLaraZ31: (2017-09-20 01:45:24)
I'll try the 86 T ecu and see what happens when he sends it. I may take you up on thatoffer, I just have to wait until bills are paid and I'm not being swallowed by school.
GodofRichy: (2017-09-20 19:37:37)
86T ecu should run your car, however keep in mind that the O2 for 85T and 86T cars are different types. The best thing for you would be to get a 87NA ecu with Nistune installed, but that's time and money in order to get the board, get Nistune installed, etc… Basically what would happen is Nistune would get installed into that 87 NA ecu, and yourself or the tuner would load a 84-85T factory tune. However if you wanted to get more power from your car, you'd have the option to tune your car accordingly(for things like larger injectors, larger turbo, cams, etc…).
JLaraZ31: (2017-09-20 23:29:14)
86T ecu should run your car, however keep in mind that the O2 for 85T and 86T cars are different types. The best thing for you would be to get a 87NA ecu with Nistune installed, but that's time and money in order to get the board, get Nistune installed, etc… Basically what would happen is Nistune would get installed into that 87 NA ecu, and yourself or the tuner would load a 84-85T factory tune. However if you wanted to get more power from your car, you'd have the option to tune your car accordingly(for things like larger injectors, larger turbo, cams, etc…).
I was thinking about doing that, but with my financial stability at the moment I cannot until the end of the semester when I'll have more time and funds to be able to do that. The 86T ECU is off of my brother's friend who isn't going to start work on his 86 until spring time; giving me time to save money for it and all. I do appreciate the information.
It wont be for a couple days til I receive it so I'll just have to wait until then.
JLaraZ31: (2017-10-09 03:09:33)
So I got the 86T ECU in and by God does it feel better, granted O2 sensor is needing to be changed but I was wondering if the titania is a direct swap in on mine or anything like that. If not what can I do to run boost safely without hurting anything?
Dunkine: (2017-10-09 19:06:15)
Need to change bungs & wiring, Titania are 17MM and Zirconium are 22MM.
Detailed info at https://dev.z31library.com/xenonzcar_archive/z31/ECUdifferences.html
FrozenZ: (2017-10-09 20:41:05)
The O2 sensor doesn't do anything that will prevent detonation, that's all in the fuel and timing maps. It's not like a modern engine management system, it's not a wideband. If you have no O2 you're going to start, cruise, and idle rich. You might find driveability issues in certain circumstances but that's all. Ir's no less safe to run boost w/o your O2 than with it.
JLaraZ31: (2017-10-12 22:23:44)
Thanks for letting me know, i have the o2 sensor for the ecu and was thinking of making an adapter to use it.
JLaraZ31: (2017-10-14 02:52:12)
So I drive with the O2 unplugged and tested everything out and all seemed normal. After getting to opperating temp I tried to go WOT to see how it would feel, but 1st gear stumbled on itself, 2nd, 3rd etc hesitated like it didn't know what it waned to do before accelerating as it should. I checked the plugs and they where kinda white, but it black smoked whenever I tried it in first. Any ideas what this could be?
JSM: (2017-10-15 21:10:56)
IAlso I've inspected the CHTS subharness closely and saw that it has some damage to it could this be my issue or would it not matter as much since the proper reading from the CHTS is going to the ECU pinouts?
Im wondering if this could be your issue. Is it fixable? If your losing connection to your ECCS I could see it continuing to throw codes. What is the damage?
JLaraZ31: (2017-10-18 16:19:25)
Im wondering if this could be your issue. Is it fixable? If your losing connection to your ECCS I could see it continuing to throw codes. What is the damage?
I will be double checking everything when I get the O2 sensor situated to make sure I don't have a similar problem as I was having with the previous ecu.
JLaraZ31: (2017-10-18 16:25:35)
So when I was trying to swap the O2 sensors I ran into a lot of trouble as in, it would not come out with an impact, breaker bar, and it started to strip. So I'm going to resort to putting another bung for it. Does anyone have a good spot or idea to where it could be placed? I was thinking before the turbo but not sure as there's not much room for me to think of areas to put it at.
FrozenZ: (2017-10-19 19:28:33)
So when I was trying to swap the O2 sensors I ran into a lot of trouble as in, it would not come out with an impact, breaker bar, and it started to strip. So I'm going to resort to putting another bung for it. Does anyone have a good spot or idea to where it could be placed? I was thinking before the turbo but not sure as there's not much room for me to think of areas to put it at.
Don't give up yet. If you haven't completely rounded the bolt yet, just go buy a proper O2 socket (if you haven't.) Hit the sensor and bung with PB blaster, go drive the car for 15 minutes, come home, hit it with PB again and then wait five more minutes before going to town on it. I'm not saying it'll pop right out, and it may not come out at all. But I've always been able to get O2s out that way.
JLaraZ31: (2017-10-19 22:02:05)
Don't give up yet. If you haven't completely rounded the bolt yet, just go buy a proper O2 socket (if you haven't.) Hit the sensor and bung with PB blaster, go drive the car for 15 minutes, come home, hit it with PB again and then wait five more minutes before going to town on it. I'm not saying it'll pop right out, and it may not come out at all. But I've always been able to get O2s out that way.
I've tried to do that and using my dads o2 socket set to pull it out but after the 2nd slip I didn't want to risk it. Took it to a muffler shop but they couldnt break it loose without slipping either and they couldn't install the bung in a the same area.
Currently I'm driving without the o2 sensor, but startups it tends to backfire, when getting into boost (at 1 psi and above) it hesitates, at wot feels like it doesnt want to accelerate, and runs lean which confuses me as i thought some said it would run richer.
I'm sure you guys may know exactlt what it could be, I'mjust tired right now from clinicals.
JSM: (2017-10-20 00:52:02)
Isn't the o2 in just the down pipe after the turbo? Can you find a used down pipe?
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Dunkine: (2017-10-20 01:16:44)
The bung is different sized too isn't it? Get a used down pipe like JFM said, but with the right sized bung and maybe the correct o2 sensor already in it [archived image: smile.png]
JLaraZ31: (2017-10-20 02:09:41)
I may try that, but taking it off might be somewhat of a problem as I don't want to snap any bolts and what not, but I was going to park it when winter hits and get a turbo back exhaust to replace the stock system, but I may see about removing the downpipe whenever i get a good amount of free time from school for that O2 sensor.
JSM: (2017-10-20 02:26:27)
This may prove useful:
http://redz31.suomiz.net/pages/turboupgrade.html88-89 turbo cars that have the T25 DO NOT use the same exhaust elbow, the exhaust turbine housing is slightly different, and contains the wastegate flapper as part of the turbine housing as opposed to part of the elbow. If you have a T25 (88-89 300zx turbo) you will need to find a Nissan T3 exhaust housing and O2 elbow off the earlier Z31 turbo cars. 280 ZX Turbo's (S130) use the same T3 as the 300ZX turbo (Z31) did in 84; the turbo is the same, but the exhaust elbow is not.
FrozenZ: (2017-10-20 18:45:39)
I've tried to do that and using my dads o2 socket set to pull it out but after the 2nd slip I didn't want to risk it. Took it to a muffler shop but they couldnt break it loose without slipping either and they couldn't install the bung in a the same area.
Currently I'm driving without the o2 sensor, but startups it tends to backfire, when getting into boost (at 1 psi and above) it hesitates, at wot feels like it doesnt want to accelerate, and runs lean which confuses me as i thought some said it would run richer.
I'm sure you guys may know exactlt what it could be, I'mjust tired right now from clinicals.
OK stupid question but are you *absolutely sure* that the ECU you borrowed is for a turbo? Like, did you check the serial? That sounds a little bit like the NA tune on a turbo. I remember somebody else had this problem ages ago. Might be a totally dumb question, but easy to check.
JLaraZ31: (2017-10-21 14:10:10)
OK stupid question but are you *absolutely sure* that the ECU you borrowed is for a turbo? Like, did you check the serial? That sounds a little bit like the NA tune on a turbo. I remember somebody else had this problem ages ago. Might be a totally dumb question, but easy to check.
Yeah, I checked it before putting it in to make sure, don't remember the serial number off the top but it said from 96 turbo 5speed federal.
JLaraZ31: (2017-10-21 14:13:03)
This may prove useful:
http://redz31.suomiz.net/pages/turboupgrade.html88-89 turbo cars that have the T25 DO NOT use the same exhaust elbow, the exhaust turbine housing is slightly different, and contains the wastegate flapper as part of the turbine housing as opposed to part of the elbow. If you have a T25 (88-89 300zx turbo) you will need to find a Nissan T3 exhaust housing and O2 elbow off the earlier Z31 turbo cars. 280 ZX Turbo's (S130) use the same T3 as the 300ZX turbo (Z31) did in 84; the turbo is the same, but the exhaust elbow is not.
Thamks, i appreciate you looking into it for me, ill see about finding the elbow for it online or fromnsomeone else depending which comes first.
FrozenZ: (2017-10-21 14:38:20)
Yeah, I checked it before putting it in to make sure, don't remember the serial number off the top but it said from 96 turbo 5speed federal.
nvm
JLaraZ31: (2017-11-09 16:14:34)
Alright so update: it's still lean, I did find 2 vacuum leaks for the breather houses. Replaced them and she perked up a little, but still lean. I am confused as to where else to check as I've tried ditating brake cleaner at anywhere thay air could get in but haven't found one (yet) wondering what input you guys may have to help me out.
JSM: (2017-11-21 20:33:57)
Alright so update: it's still lean, I did find 2 vacuum leaks for the breather houses. Replaced them and she perked up a little, but still lean. I am confused as to where else to check as I've tried ditating brake cleaner at anywhere thay air could get in but haven't found one (yet) wondering what input you guys may have to help me out.
Saw this on FB. Not sure if you were looking for one. https://www.facebook.com/groups/9327…55332868872867
JSM: (2017-12-29 02:52:10)
You ever figure this out?
JLaraZ31: (2018-06-20 20:23:27)
You ever figure this out?
haven't been on here as much as school has been royally throttling me. I did, it was the Fuel pressure regulator wish I couod have confirmed way sooner but at least it was fixed.