bsmuwk Posted June 13, 2012 Share Posted June 13, 2012 Car ran out of gas on me and I hadn't realized (illegal tow bent up my fuel tank a tad so the gauge reads off). COINCIDENTALLY, I did the FSM test for the AFM and it failed (car was running weird beforehand anyway) put it in a friends car and his car wouldn't run with it either. So low and behold I did an entire 300ZX ECU swap from an 84-86 and the car starts and runs. However, it's running like crap. If I unplug the CHTS the car will rev nicely but under load it will cut out and backfire around 4k rpm. If I have the CHTS plugged in, the car will have a surge in idle, and will fall on its face with just the merest of touch to the throttle. I have new plug wires in the car now (they shocked me when I touched them), new TPS on order, new cap and rotor on order, etc. Any ideas where this could lead? I'm assuming the 300ZX ECU's code blinking should provide me some info as to how I should attack the situation, but I'm curious where everyone else stands on this. Thanks folks. Quote Link to comment Share on other sites More sharing options...
Heroez Posted June 13, 2012 Share Posted June 13, 2012 Do the tune up parts first. These cars are known to be problematic since the 80s. 3 ASE mechanics have had my 83 turbo for a month trying to figure out why its backfiring and stumbles at 2-3k RPM. Quote Link to comment Share on other sites More sharing options...
ArchetypeDatsun Posted June 13, 2012 Share Posted June 13, 2012 I hope im not thread jacking but I have the same damn problem, mine has 87 Z31 ECU & MAF the funny thing though it use to run really good before but after my head needed work it ran like crap. After the rebuild of the head it runs a little better when the car is cold, once it's warm is stummbles and it feels like It has loss of power. Don't know If your car does the same? Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 I should have those tune up parts in a day or so, but damnit. It was just confusing. The AFM tests bad, I was expecting it to fail, which is why I had my 300ZX swap ready to go in. No issue there, put everything in and the car runs. There IS fuel pressure and fuel flowing. I can clamp off the return line and there is no change in how the car runs, so I'm not associating this with fuel delivery. It seems whatever's happening is ignition related. A very bad misfire with any touch of the throttle. It's got me stumped. I'm ready to rip every wire out of the car and rewire everything and do an LS1 swap while I'm at it. lol Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 13, 2012 Share Posted June 13, 2012 (edited) I know it's a dumb question, but have you replaced the CHTS? Also when/if you replaced it did you replace it with a CHTS from a 280ZX or a CHTS from a Z31? I swear I read somewhere that the Z31 CHTS is slightly different and that it doesn't seem to operate correctly if you use it on the L28. Also is your O2 sensor hooked up and working? Also check the ECU codes. Another thing I've read is that if the Z31 chopper wheel is placed in the Crank Angle Sensor upside down the car won't run right, but I've heard it won't idle so I don't know on that one. Have you tried shaking the harness connected to the ECU to make sure there's not a wiring problem somewhere? Also when was the last time you replaced your coil/igniter? Edited June 13, 2012 by DuoWing Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 I know it's a dumb question, but have you replaced the CHTS? Also when/if you replaced it did you replace it with a CHTS from a 280ZX or a CHTS from a Z31? I swear I read somewhere that the Z31 CHTS is slightly different and that it doesn't seem to operate correctly if you use it on the L28. Also is your O2 sensor hooked up and working? Also check the ECU codes. Another thing I've read is that if the Z31 chopper wheel is placed in the Crank Angle Sensor upside down the car won't run right, but I've heard it won't idle so I don't know on that one. Have you tried shaking the harness connected to the ECU to make sure there's not a wiring problem somewhere? Also when was the last time you replaced your coil/igniter? I haven't replaced the CHTS. The Z31 CHTS is too short to use in the L28 so I wouldn't be getting a decent reading for that anyway. My O2 sensor is hooked up, but I have no clue if its working. The Z31 chopper wheel was removed from the Z31 distributor I got with my swap. I installed it in the same orientation it was in when I received the Z31 distributor. The harness has Z31 connectors. I've shaken and cleaned every damn plug on the engine. Coil and igniter haven't been replaced. The car is getting nice blue spark so I would imagine that wouldn't be the issue? Seems just when the CHTS is unplugged the car has balls until 4k RPM then eats dirt. Quote Link to comment Share on other sites More sharing options...
Heroez Posted June 13, 2012 Share Posted June 13, 2012 Just to add to the confusion, all good working 280zxt AFMs test bad according to the manual. I figured that out the hard way. Eventually we tested 3 known good turbo air flow meters and they all failed the resistance tests. So the manual isn't flawless. As for your other problem, its temperature related so look at temperature relevant parts. If your spark is weak, you may need that IC module on the coil bracket. All this is advice from a guy that has a similar problem, gave up, took it to some ASE certified mechanics, and they can't seem to make progress either. I can only conclude that the problem is the ECCS in general. Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 Well, I have a TON of spare parts for the car that I got from my dad when he gave it to me a while back. It's all ignition related, I know that now for sure with the unplugging of the CHTS, but my question around the issue is WHY? What does the CHTS do when its unplugged? Quote Link to comment Share on other sites More sharing options...
DuoWing Posted June 13, 2012 Share Posted June 13, 2012 When the CHTS is unplugged the ECU basically ignores all sensors and runs off it's pre-determined maps, but part of that is also the fact that those pre-determined maps are also somewhat designed to get you around, but at least as I understand you'd essentially be in limp mode. When the CHTS is unplugged the car will generally run more rich. When everything is working properly the car will then run as it's supposed to, but with a bad CHTS basically these things default to where the car is thinking it's running extremely cold and it's just dumping fuel and making the car run really rich which makes it bog, backfire, idle poorly, etc. I would say replace your CHTS and go from there. I believe the sensor isn't too expensive. Quote Link to comment Share on other sites More sharing options...
Heroez Posted June 13, 2012 Share Posted June 13, 2012 There is no limp mode, but it does have fail safe mode. After 30 years the wiring is a total loss especially the wires near heat from the engine. How far will Grandma Z run if we keep picking her up? Would you be patching up the EFI if it was from the 50s? Maybe Megasquirt is the propper fix. Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 I'll be ordering the CHTS tonight then. Just for clarification, I went out and red the blinks on the ECU and came up with all of these: 13 - Cylinder Head Temp Circuit 21 - Ignition Signal missing primary circuit 23 - Throttle valve switch 24 - Neutral Park Switch 31 - AC stuff 34 - Detonation Sensor 41 - Fuel Temp Sensor circuit In regards to having the car run, I still have my 280ZX knock sensor hooked up. The car doesn't have a fuel temp sensor like the Z31, nor does it have the Neutral park switch. So I'm assuming codes 24, 31, 34, and 41 are not needed. So my problems lay withing 13, 21 and 23? Does anybody else have any inherent fault codes when running the Z31 ecu on an S130? Quote Link to comment Share on other sites More sharing options...
JSM Posted June 13, 2012 Share Posted June 13, 2012 Before you order the parts, check the continuity from the wire that leads from CHTS to the pin on the ECU. You'll have to look in the FSM for the Pin #. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 13, 2012 Share Posted June 13, 2012 " I can clamp off the return line and there is no change in how the car runs, so I'm not associating this with fuel delivery. " I would rethink that portion of your diagnosis. " Eventually we tested 3 known good turbo air flow meters and they all failed the resistance tests. So the manual isn't flawless. " I think that went to the reading of the meter and having it in the wrong range (or in autoranging) which confused you. I have NEVER had an AFM that failed the test in the book that wasn't bad. "Known good" doesn't mean that they can't be bad, or won't have drivability problems, or that when they test 'bad' that the impact they have on the driveability is in any way significant...especially if your wiper arm doesn't dwell in the 'bad' area and moves across it quickly.My experience with the Manual in regards to component tests has been spot-on, I would not ding it in respect to troubleshooting the EFI or ECCS System especially! Quote Link to comment Share on other sites More sharing options...
Heroez Posted June 13, 2012 Share Posted June 13, 2012 I only did one of the resistance tests. cgsheen and hogman did the other two and the results were within 1 digit. It is true that my inexperience and autorange meter tricked me. If you say the manuals tests are accurate, then I must reconsider my views given your experience and credentials. I am just a confused hobbiest pushed to the brink of madness by a car problem I dont understand. Readers, please disregard my earlier remarks. I was letting my emotions dictate my words, and allowing my ignorance in these matters to come out. Im sorry for that. Your car troubles hit a little too close to home. It sucks to be helpless, and sucks that nobody near me can fix my car, and all I can do is watch it rot away. Maybe its time for me to let go of the turbo dream. Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 I put a fuel pressure gauge on the line right after the fuel filter, fuel pressure at idle is 32psi and when I rev the car (with chts unplugged) it sits steady at 36psi. I don't know accuracy of the gauge. Quote Link to comment Share on other sites More sharing options...
B. Whisky Posted June 13, 2012 Share Posted June 13, 2012 (edited) I can't speak to the applicability of my experience to the po's, as I haven't coverted to the z31 efi yet, but my zxt would bog out at ~4k, and backfire through the intake. After testing at the ecu plug the first issue I encountered was the tps. Turned out I had an intermittent open circuit, which turned out to be an extremely corroded wire in the boot at the connector of the tps itself. It was broken completely and just barely making contact. Addressing that revealed the tps to be mechanically damaged inside, so it wouldn't stay locked to the throttle butterfly. Swap another in, adjusted, and i was good to go. As for the chts, the way I have my car set up with all the idle speed controls removed, my engine floods out if that connection is lost. If I cycle the ignition of and on, I can hear my injectors click once, and my oil smells like gas if I try that enough times. I just skimmed through this thread, but if the backfiring you experience is through the intake, I want to say lean towards the tps, or rather, check that circuit. Hope this helps. Edited June 13, 2012 by B. Whisky Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 Well, I'll be swapping in a new TPS as soon as it comes in the mail. I'll be adjusting per fsm. Checking for continuity at the ecu plug for the chts will be done later today when I find my multimeter. I can't remember where I put it in the past day. Sad? Lol Quote Link to comment Share on other sites More sharing options...
B. Whisky Posted June 13, 2012 Share Posted June 13, 2012 Since your getting a new one, open up your current tps by grinding off the two rivets on the back. Looking inside should give you a good idea of whats going on in there. It's a pretty simple device, and I'm inclined to say it shouldn't just go bad like a sensor giving resistance values to the ecu. In my case, I'm certain it broke from me trying to adjust it out of its range of movement, before I went and referenced the fsm and found the faulty wire. Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 Well the TPS is replaced and while I still can't find my multimeter, I played with the adjustment of the TPS and it seemed like there was a slight change in behavior, but no dice. If I had the tps unplugged and tried revving, the engine just stalled. I'll assume the tps is functional at this point, but at an unknown adjustment (for now). Quote Link to comment Share on other sites More sharing options...
bsmuwk Posted June 13, 2012 Author Share Posted June 13, 2012 There is no intake backfire, It's running rich. Quote Link to comment Share on other sites More sharing options...
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