with my little POS 88 300zx!
I know this is a Supra Forum but a friend (also on here) suggested I should try, so I try.
This is something my bf wrote in another forum (300zxclub), so please forgive me if it doesnt make sense at times:
Model Year : 1988
Body Style: 2+2
Trim: GLL
Drive-train: Turbo/Automatic
(Canadian option package)
Introduction:
Basically when we first picked up the car I noticed that it was a bit sluggish and idled rough, I figured that it just needed a tune up. After having driven the car only about an hour or so I noticed that it was becoming more and more difficult to drive. Too me it seemed to be running pig rich. I happened to be visiting my snap-on dealer and the car was turning over slowly. He load tested my battery and alt, Battery showed 14amps and the alt produced 12 amps. Later that night the digital dash was cutting out and the engine was struggling and stalling. I swapped out the battery with a friends optima drycell to get me home so I could grab a good battery from my house (He needed his battery back and I figured mine was just dead.) and return his. With his battery the car actually responded quite well, but was still a bit sluggish out of the hole. When I returned his battery and put mine in the car wouldn’t idle, would hold an rpm or speed for only a few seconds then not respond to the throttle whatsoever and fall back to an idle or stall completely out. I figured that maybe my battery was no good, so I borrowed his back with the promise of driving it back in my service van. Now with his battery the car acted up completely and ended up having to be towed home. I recharged my battery and installed a new bosch alternator into the car with the hopes that this would solve the problem. Did not, though now the charging system is working great.
At first I just fiddled around with connectors, trail and error type deal until I found that with the AFM disconnected the car actually ran extremely smooth and responded well to the throttle. I replaced the AFM with a used unit that I personally pulled from a good running 88 2+2 Turbo GLL automatic… the exact duplicate of our car but black/charcoal gray, and the problem still persisted. Though now with the AFM disconnected the car isn’t quite as receptive to the throttle, but that might just be my imagination.
I have the 1988 Nissan factory service manual in PDF that I downloaded from carfiche.com I think it was… it’s been about a year since I downloaded it. I followed the instructions to the T in the manual and this is what I found
With the AFM plugged in:
Engine seems to run extremely rich, while also running very rough. If you manage to actually get the engine to race at all it will not hold an rpm for more than a few seconds. The idling seems to struggle and it seems as though the engine is not firing on all cylinders. The car was semi drivable like this but consumes huge amounts of fuel, even by Z standards. The condition has worsened to the point that it is no longer drivable. The engine struggles too much to get the car moving never mind up to rpm.
With the AFM disconnected:
The engine runs and idles smooth, though at about 1300 rpm. Obviously the engine will not rev past 1900 rpm, but otherwise sounds beautiful which suggests to me that the issue is not mechanical and that it is majorly related to the AFM.
I replaced the AFM with a good used unit that came out of a good running car (88 Turbo 2+2 GLL). This did not solve the problem at all. I did notice that on the "female" plug it is missing one connector in slot (A) while there is a corresponding male plug in slot (A).
After pulling the codes from the ECU this is what I was able to gather together.
Codes
12 - Air Flow Meter
23 - Idle Switch Circuit
42 - Fuel Temperature Circuit
Code 12 :
After following all diagnostics on the afm I have found this.
Reading 13.38 volts at the AFM, 14.36 volts at the battery
Reading 0.6 and 0.7 ohms respectively
Reading 2.7-2.8 volts at idle
Reading about 3.5 volts at about 4000 rpm, but I notice that from basically 3000 to 4000 rpm the voltage hovers around 3.5-3.8 volts with little movement. Does not seem to be following a linear path as I would imagine that it should do.
Also just to eliminate the possiblity there is no volt reading from the AFM with it dissconnected.
Code 23:
Found no issue with the throttle position sensor. Got a reading of 8.33 volts with the fuel pedal not being pressed. Depressing the fuel pedal closed the switch as it should, and showed no voltage.
Code 42 :
Reading a constant 5.0 volts which suggests that there is a possible short in the line for the fuel temp circuit. With the lead disconnected from the fuel temp sensor I still get 5.0 volts. I only tested the fuel temp sensor disconnected when the engine was completely up to temp, and I got ~ 3.5 ohms.
After that someone said it might be an intake leak but we couldnt hear anything that would suggest an intake leak. So yeah:
I have not been able to find any hints of a vacuum/boost leak. I disconnected a couple of different vacuum hoses to be sure and the engine bucked (with afm plugged in) and near stalled.
While I have not pulled any codes from the ecu this time the "Check engine" LED on the ECU is still on (I have the ecu pulled out).
I started the car with the afm dissconnected and let it warm up. It idles at about 1300 rpm but is showing two bars on the dash. Usually at idle they only show one. I plugged the afm back in and the car idled stable at 1200 rpm and didn't sound like it was missing or anything and also was drivable. Though I did notice that the inital throttle response was hesitant but it didn't buck or kick. After driving the car around a little bit it started to act up, I was a bit agitated with the car and did a rockford u-turn that ended up being 3-360's, though afterwards the engine stopped acting up other than the hesitation at the beginning of the pedal. After about 3500 rpm the engine seemed to come all the way on but does run a little bit hot up there.
After shutting the car off and starting it again it was undrivable and I had to disconnect the afm to get the car home. When I got back home I started playing with the idle-up solinoid and it didn't seem to help at all. I let the car idle a little bit with the afm disconnected and reconnected the afm and it idled up and was running smooth. Idle was holding at about 1500 rpm with 2 bars on the digi-tach. Unfortunately I do not have a proper vacuum gauge so I'm not able to get an accurate reading.
After playing around with the connectors a bit I found that after the 20 second idle up with the afm plugged in the engine would idle down and go up to 3 or sometimes 4 bars and would struggle to idle eventually stalling. I played around with disconnecting the afm and plugging it back in and it started to get a bit better. Sometimes for a few seconds it would struggle after the idle up then it would smooth out, but would idle at about 1100 rpm with 2 to 3 bars. I re-adjusted the timing, which turned out to be out quite a bit and now the car idles smooth at 1000rpm but still shows 2 bars and hesitates off the throttle. Under WOT accellerating the turbo is all there, but doesn't sound as pernounced as it was in my 86 (2+2 GLL Turbo Auto) but it was still a little bit sluggish and wasn't able to accelerate past 130 kph with any major increase in speed. I also noticed that the kick down for the transmission doesn't seem to be working and it is consistantly shifting at 4400 rpm, where my 86 would shift at 5600 rpm.
It is still consuming astronomical amounts of fuel, and will back-fire from time to time when I go from idle to WOT, but it is driving somewhat decently and idling smoothly at 1000 rpm. Still showing two bars on the digi-tach.
Attemped to adjust the throttle position sensor, as I move it counter-clockwise the motor will make a bit of a sucking sound through the airfilter and will drop to about 700 rpm and struggle to idle, jumping up to 3 bars on the digi-tach. If I leave it at the point just above where the switch activates, the engine idles smooth at about 1000 to 1100 rpm. (During writing of this the engine has been idling since the beginning and I'm adjusting things as I go, but I have not restarted the engine)
Restarted the engine, it went straight to 1000 rpm and idled smoothly, blipping the throttle to 5000 rpm I let it fall back down to idle. It dropped to 700 rpm and struggled to run. I restarted the engine again and it went to 700 rpm and struggled. This is with the TPS set above the idle mark.
Setting the TPS clockwise past the switch point I started the car. For a few seconds it held a perfect 800rpm with only one bar on the digi-dash and idled smoothly. After that it started to struggle but somewhat responded to the throttle. After restarting it went straight back into trying to die. If i hold the throttle at 2200 rpm the engine will stay there smooth for about 10 seconds then start to fall off and struggle again.
Tried the same as above but with the TPS set correctly and it did the same things, except idled about 200 rpm higher.
Now with the AFM dissconnected it will only idle with the TPS set past the idle point. If I have it on the idle point it will not always start. It's a few month old TPS from nissan. If I let the car idle for a minute or two with the AFM disconnected then plug it back in the engine will idle nicely at 1000 to 1100 RPM with two bars on the digi-dash. If I adjust the TPS counterclockwise back to the point where the relay kicks and it starts to idle rough it will stall. If I leave it just above that point it idles well and responds decently to the throttle, but if I hammer on the throttle too hard it will back fire. Still showing two bars on the digi-dash.
The only thing out of norm that I've noticed is that according to the FSM the bottom two prongs on the TPS are supposed to be the idle switch, yet when I tested this unit it was the top two. Is this an error in the FSM or a mess up on my TPS?
I managed to get the car to run decently and took it for a longer drive around my town... Near the end of the run I noticed that the headlights were getting excessively dim and the car was running worse. About 5km from my house the dash started to kick in and out and I realised that it was running out of power. By the time I got the car home It wouldn't go past 3000 rpm freewheeling. I remember when I took the voltage reading off the AFM it was supposed to be the same as the battery but it was 13.38 volts where the battery was 14.36 volts. I noticed that a couple of other readings where a couple volts lower than they were supposed to be according to the FSM. My question: Is it possible that a bad connection somewhere, causing a voltage drop, is causing the ECU to missread the information being prosented? If this is a possibility where would be the best place to start looking?
I havn't got around to testing the resistance across the terminals but I was showing a definate voltage drop when taking messurements following the directions in the FSM. Again: When testing the battery feed at the afm I was getting 13.38 volts while at the battery terminals I was getting 14.36 volts. When testing the idle switch at the ECU I got ~8.3 volts when it should have been about 10 according to the FSM.
Also all of the pins on the AFM itself are there, but the female receptical on the wiring harness is missing a receptical in slot "A", I pulled back the boot to see if it slipped out or something but I find no evidence of there ever have been a wire there.
According to the tests described in the FSM the AFM is ok, but I will check the resistance based off your readings tonight.
I am concerned that there is a voltage drop to the electrical system from the battery and mabye the possibility that the hot wire from the Alt to the batt is broken or causing an issue.
So I'm left with two basic avenues to follow: check the AFM again and discount it as the issue. The only actual code that has seemed to be right was the fuel temp sensor, which is obviously a short in the line but I do not have another 88 GLL harness to replace mine with.
Now someone said that something similar happened to him and it was caused by the ECU... so we got an ECU out of the 88 300zx from a friend. Unfortunately he has a standard car, not an automatic... so we are not sure if that effects anything. Well, result was: Nothing changed, my car still sucks ass! HELP!!!
I know this is a Supra Forum but a friend (also on here) suggested I should try, so I try.
This is something my bf wrote in another forum (300zxclub), so please forgive me if it doesnt make sense at times:
Model Year : 1988
Body Style: 2+2
Trim: GLL
Drive-train: Turbo/Automatic
(Canadian option package)
Introduction:
Basically when we first picked up the car I noticed that it was a bit sluggish and idled rough, I figured that it just needed a tune up. After having driven the car only about an hour or so I noticed that it was becoming more and more difficult to drive. Too me it seemed to be running pig rich. I happened to be visiting my snap-on dealer and the car was turning over slowly. He load tested my battery and alt, Battery showed 14amps and the alt produced 12 amps. Later that night the digital dash was cutting out and the engine was struggling and stalling. I swapped out the battery with a friends optima drycell to get me home so I could grab a good battery from my house (He needed his battery back and I figured mine was just dead.) and return his. With his battery the car actually responded quite well, but was still a bit sluggish out of the hole. When I returned his battery and put mine in the car wouldn’t idle, would hold an rpm or speed for only a few seconds then not respond to the throttle whatsoever and fall back to an idle or stall completely out. I figured that maybe my battery was no good, so I borrowed his back with the promise of driving it back in my service van. Now with his battery the car acted up completely and ended up having to be towed home. I recharged my battery and installed a new bosch alternator into the car with the hopes that this would solve the problem. Did not, though now the charging system is working great.
At first I just fiddled around with connectors, trail and error type deal until I found that with the AFM disconnected the car actually ran extremely smooth and responded well to the throttle. I replaced the AFM with a used unit that I personally pulled from a good running 88 2+2 Turbo GLL automatic… the exact duplicate of our car but black/charcoal gray, and the problem still persisted. Though now with the AFM disconnected the car isn’t quite as receptive to the throttle, but that might just be my imagination.
I have the 1988 Nissan factory service manual in PDF that I downloaded from carfiche.com I think it was… it’s been about a year since I downloaded it. I followed the instructions to the T in the manual and this is what I found
With the AFM plugged in:
Engine seems to run extremely rich, while also running very rough. If you manage to actually get the engine to race at all it will not hold an rpm for more than a few seconds. The idling seems to struggle and it seems as though the engine is not firing on all cylinders. The car was semi drivable like this but consumes huge amounts of fuel, even by Z standards. The condition has worsened to the point that it is no longer drivable. The engine struggles too much to get the car moving never mind up to rpm.
With the AFM disconnected:
The engine runs and idles smooth, though at about 1300 rpm. Obviously the engine will not rev past 1900 rpm, but otherwise sounds beautiful which suggests to me that the issue is not mechanical and that it is majorly related to the AFM.
I replaced the AFM with a good used unit that came out of a good running car (88 Turbo 2+2 GLL). This did not solve the problem at all. I did notice that on the "female" plug it is missing one connector in slot (A) while there is a corresponding male plug in slot (A).
After pulling the codes from the ECU this is what I was able to gather together.
Codes
12 - Air Flow Meter
23 - Idle Switch Circuit
42 - Fuel Temperature Circuit
Code 12 :
After following all diagnostics on the afm I have found this.
Reading 13.38 volts at the AFM, 14.36 volts at the battery
Reading 0.6 and 0.7 ohms respectively
Reading 2.7-2.8 volts at idle
Reading about 3.5 volts at about 4000 rpm, but I notice that from basically 3000 to 4000 rpm the voltage hovers around 3.5-3.8 volts with little movement. Does not seem to be following a linear path as I would imagine that it should do.
Also just to eliminate the possiblity there is no volt reading from the AFM with it dissconnected.
Code 23:
Found no issue with the throttle position sensor. Got a reading of 8.33 volts with the fuel pedal not being pressed. Depressing the fuel pedal closed the switch as it should, and showed no voltage.
Code 42 :
Reading a constant 5.0 volts which suggests that there is a possible short in the line for the fuel temp circuit. With the lead disconnected from the fuel temp sensor I still get 5.0 volts. I only tested the fuel temp sensor disconnected when the engine was completely up to temp, and I got ~ 3.5 ohms.
After that someone said it might be an intake leak but we couldnt hear anything that would suggest an intake leak. So yeah:
I have not been able to find any hints of a vacuum/boost leak. I disconnected a couple of different vacuum hoses to be sure and the engine bucked (with afm plugged in) and near stalled.
While I have not pulled any codes from the ecu this time the "Check engine" LED on the ECU is still on (I have the ecu pulled out).
I started the car with the afm dissconnected and let it warm up. It idles at about 1300 rpm but is showing two bars on the dash. Usually at idle they only show one. I plugged the afm back in and the car idled stable at 1200 rpm and didn't sound like it was missing or anything and also was drivable. Though I did notice that the inital throttle response was hesitant but it didn't buck or kick. After driving the car around a little bit it started to act up, I was a bit agitated with the car and did a rockford u-turn that ended up being 3-360's, though afterwards the engine stopped acting up other than the hesitation at the beginning of the pedal. After about 3500 rpm the engine seemed to come all the way on but does run a little bit hot up there.
After shutting the car off and starting it again it was undrivable and I had to disconnect the afm to get the car home. When I got back home I started playing with the idle-up solinoid and it didn't seem to help at all. I let the car idle a little bit with the afm disconnected and reconnected the afm and it idled up and was running smooth. Idle was holding at about 1500 rpm with 2 bars on the digi-tach. Unfortunately I do not have a proper vacuum gauge so I'm not able to get an accurate reading.
After playing around with the connectors a bit I found that after the 20 second idle up with the afm plugged in the engine would idle down and go up to 3 or sometimes 4 bars and would struggle to idle eventually stalling. I played around with disconnecting the afm and plugging it back in and it started to get a bit better. Sometimes for a few seconds it would struggle after the idle up then it would smooth out, but would idle at about 1100 rpm with 2 to 3 bars. I re-adjusted the timing, which turned out to be out quite a bit and now the car idles smooth at 1000rpm but still shows 2 bars and hesitates off the throttle. Under WOT accellerating the turbo is all there, but doesn't sound as pernounced as it was in my 86 (2+2 GLL Turbo Auto) but it was still a little bit sluggish and wasn't able to accelerate past 130 kph with any major increase in speed. I also noticed that the kick down for the transmission doesn't seem to be working and it is consistantly shifting at 4400 rpm, where my 86 would shift at 5600 rpm.
It is still consuming astronomical amounts of fuel, and will back-fire from time to time when I go from idle to WOT, but it is driving somewhat decently and idling smoothly at 1000 rpm. Still showing two bars on the digi-tach.
Attemped to adjust the throttle position sensor, as I move it counter-clockwise the motor will make a bit of a sucking sound through the airfilter and will drop to about 700 rpm and struggle to idle, jumping up to 3 bars on the digi-tach. If I leave it at the point just above where the switch activates, the engine idles smooth at about 1000 to 1100 rpm. (During writing of this the engine has been idling since the beginning and I'm adjusting things as I go, but I have not restarted the engine)
Restarted the engine, it went straight to 1000 rpm and idled smoothly, blipping the throttle to 5000 rpm I let it fall back down to idle. It dropped to 700 rpm and struggled to run. I restarted the engine again and it went to 700 rpm and struggled. This is with the TPS set above the idle mark.
Setting the TPS clockwise past the switch point I started the car. For a few seconds it held a perfect 800rpm with only one bar on the digi-dash and idled smoothly. After that it started to struggle but somewhat responded to the throttle. After restarting it went straight back into trying to die. If i hold the throttle at 2200 rpm the engine will stay there smooth for about 10 seconds then start to fall off and struggle again.
Tried the same as above but with the TPS set correctly and it did the same things, except idled about 200 rpm higher.
Now with the AFM dissconnected it will only idle with the TPS set past the idle point. If I have it on the idle point it will not always start. It's a few month old TPS from nissan. If I let the car idle for a minute or two with the AFM disconnected then plug it back in the engine will idle nicely at 1000 to 1100 RPM with two bars on the digi-dash. If I adjust the TPS counterclockwise back to the point where the relay kicks and it starts to idle rough it will stall. If I leave it just above that point it idles well and responds decently to the throttle, but if I hammer on the throttle too hard it will back fire. Still showing two bars on the digi-dash.
The only thing out of norm that I've noticed is that according to the FSM the bottom two prongs on the TPS are supposed to be the idle switch, yet when I tested this unit it was the top two. Is this an error in the FSM or a mess up on my TPS?
I managed to get the car to run decently and took it for a longer drive around my town... Near the end of the run I noticed that the headlights were getting excessively dim and the car was running worse. About 5km from my house the dash started to kick in and out and I realised that it was running out of power. By the time I got the car home It wouldn't go past 3000 rpm freewheeling. I remember when I took the voltage reading off the AFM it was supposed to be the same as the battery but it was 13.38 volts where the battery was 14.36 volts. I noticed that a couple of other readings where a couple volts lower than they were supposed to be according to the FSM. My question: Is it possible that a bad connection somewhere, causing a voltage drop, is causing the ECU to missread the information being prosented? If this is a possibility where would be the best place to start looking?
I havn't got around to testing the resistance across the terminals but I was showing a definate voltage drop when taking messurements following the directions in the FSM. Again: When testing the battery feed at the afm I was getting 13.38 volts while at the battery terminals I was getting 14.36 volts. When testing the idle switch at the ECU I got ~8.3 volts when it should have been about 10 according to the FSM.
Also all of the pins on the AFM itself are there, but the female receptical on the wiring harness is missing a receptical in slot "A", I pulled back the boot to see if it slipped out or something but I find no evidence of there ever have been a wire there.
According to the tests described in the FSM the AFM is ok, but I will check the resistance based off your readings tonight.
I am concerned that there is a voltage drop to the electrical system from the battery and mabye the possibility that the hot wire from the Alt to the batt is broken or causing an issue.
So I'm left with two basic avenues to follow: check the AFM again and discount it as the issue. The only actual code that has seemed to be right was the fuel temp sensor, which is obviously a short in the line but I do not have another 88 GLL harness to replace mine with.
Now someone said that something similar happened to him and it was caused by the ECU... so we got an ECU out of the 88 300zx from a friend. Unfortunately he has a standard car, not an automatic... so we are not sure if that effects anything. Well, result was: Nothing changed, my car still sucks ass! HELP!!!
